Major issue in TS100 code - Chapter 1. ADC

[sandmanRO]

Three weeks ago, while in the look for a portable iron I ended-up purchasing a Miniware TS100 unit. I was petrified by the crudeness of delivered factory firmware and I was looking for alternatives. I came across your firmware, but honestly I was not significantly impress as compared to factory firmware. Left without alternatives I had no choice but build my own. Nevertheless, I though I would share with you some of the issues I noticed in your code. No offense gents, but let me just say that your code works by pure accident. In fact, it's one tick away from failure. Where I should start? Oh well...there we go:

1. Before bells and whistles let's focus first on what is matter the most, that data acquisition. a. The injected ADC1 channel is not triggered when you believe it does. In the way the TIM2 CTR1 was configured, the injected ADC1 (temperature reading) is triggered on period complete (as opposed to pulse complete) of TIM2 CTR1, that is, right when the heating is about to begin. Only the use of the smallest sampling time and the delay induced by software starting of TIM3 CTR1 (the actual power PMD control) from TIM2 CTR4 period complete interrupt saves the execution from total failure, that is reading the temperature while the tip heater is on. b. All the STM32 documentation specifically state not to simultaneously sample the same channels with both ADC1 and ADC2 when dual ADC mode is used as this could lead to conversion errors, and yet, the code does exactly just that, on both regular and injected channels (ADC2 duplicates the readings of ADC1, same channels at the same time). c. The input voltage readings are not synchronized with the PID. As the input voltage drops during heating window, you get a collection of random values between maximum voltage (voltage at idle) and minimum voltage (voltage during heating window). No wonder the voltage readings, even with the 16 sample DMA buffer averaging + extra post acquisition (8 samples deep) average filtering, jump all over the place. d. During the switch between 'fast' and 'slow' PWM, for some unknown reasons you took the approach of changing everything, tick rate, total tick count and the pulse count of TIM2 counters. This leads to variable PID cycle rates which in turn makes the full scale synchronization with all ADCs virtually impossible. e. The LIS2DH (the accelerometer with the latest revision of TS100) is not configured properly (if at all - the code is attempting to configure the interrupt registers using a wrong address with unknow side effects). No wonder your code ended up getting the accelerometer data in pulled mode. Otherwise getting the accelerometer data in pulled mode is not necessarily a bad thing as it allows to do some extra processing at your won pace. However, you activated the high pass filter which means you are eliminating exactly the static acceleration (Earth gravity) that is critical for orientation discrimination. No doubt, LIS2DH orientation data sucks. I agree. As the LIS2DH does not provide low pass filtering (only high pass filter), in my implementation I ended up using a simplified STD (standard deviation) filter, to determine if an orientation change was triggered by a temporary acceleration or by static acceleration (Earth gravitational field). Only the last one would be consider for an orientation change as I don't want the display to flicker every time I move the iron left or right. Moreover, LIS2DH generates orientation data only for the axis with maximum acceleration. So if the tip of the iron is oriented significantly upwards / downwards (accelerometer X axis) you will no longer get orientation for the axis of interest (accelerometer Y axis) in respect with left/right handed display orientation so I'm compensating this by using a software algorithm that considers the actual X, Y, Z accelerations as provided by the accelerometer. Now I'm keeping the iron only in automatic orientation mode by default as finally it's working consistently.

Well, these were the DAQ (data acquisition) problems. Here are my solutions. For start let's review the correct daq sequence:

As the injected ADC channels are triggered by the RISING edge of the TIM2 CTR1 counter (and NOT by the falling edge of the counter output), to get the timing right, it is critical then that TIM2 CTR1 is configured as ACTIVE LOW (sConfigOC.OCPolarity = TIM_OCPOLARITY_LOW;) Moreover, to avoid data conversion errors, I use the ADCs as follow: ADC1 regular, rank 1 through 4 for reading handle temperature, injected ADC1 ranks 1-4 for tip thermocouple, injected ADC2 ranks 1-4 for voltage input readings, both injected channels with a post acquisition (8 slots deep) average filter. Anything, regular and injected, use the same sampling time of ADC_SAMPLETIME_28CYCLES_5 (anything lower than this would not be enough to correctly measure a 'large' signal like when the input voltage has a value of 24V, even if internally divided by the R20 (75kOhm) and R21(10kOhm) resistive divider). Moreover, the samples are updated in ONE single place, that is within the PID loop. All other calls within app would call for filtered (average) result. This way we keep everything synchronized. You guys do that and you will be amazed how stable everything becomes (so stable that several times during development I though the STM32 just hanged on me...nope...only scary stable readings). For PID I'm using a simple, yet fully effective self-decaying integrator and nothing else (no proportional, no derivative term). When integrating I'm taking into account the PID cycle period as integration time, and as decaying factor I'm using the thermal inertia of the tip (thermal mass) that makes perfect physical sense. Despite its simplicity, it turned out to be so accurate that I even had to include a gain of 2 when integrating for compensating for the fact we are actually pumping current through the tip only half the time of TIP2 CTR4 pulse as the actual TIM3 CTR1 that drives the power has 50% duty cycle.

Regarding timers, in my implementation I keep the TIM2 period (total ticks) fixed at 199 ticks and change only the TIM2 frequency (TIM2 prescaler at 4000 and 8000 respectively) and the pulse width of TIM2 CTR4 as requested by the PID. The TIM2 Period / PID Cycle will switch only between fixed 5Hz and 10Hz rates so everything stays synchronized.

I would stop here. If I start talking about user interface, it would take me days.

Below it's a glimpse of my implementation. All sort of bells and whistles like OLED contrast, enhanced graphics, double click button events, single / dual language support + spot on data acquisition w/ augmented automatic display orientation. Despite my best efforts I could not manage to get more than two languages fit in at a time. In my implementation each language adds about 10k to the hex file. With one language the hex is about 113k, two languages about 123k, three languages in excess of 132k so it would no longer fit in.

Idle Screen (graphic mode) Buttons pop-up with animation (they 'inflate' with animation from the small buttons) when sensing movement so the user would know which button does what No tip display Tip hot notification

[Ralim]

Hello,

Okay there is a fair bit here to unpack, so I will probably be back later on with more to this reply as I have time to check things out.

But I will address the things I can now.

a) Timer+ADC setup may be wrong

Honestly back when this was coded forever ago I did do a fair bit of validation on this, but it could absolutely be wrong. Would definitely love to see a PR if you feel like making one 😂 But, I absolutely will dig into this as you are probably right here. Ill have to get back on this at some point as it will take more time than I have right now.

b) Dual sampling of two the two adc's at once which may be bad

Could you point to a reference for this? Back when this was written it was written in reference to the STM32F1 reference manual. So would love to know where this from :)

c) Input adc readings are not sampled inline with PID

So the intent of the current code is that we want to measure a mix between voltage during sag and at idle to allow for showing both to the user, though this is probably pointless at this point in time.

d) Not certain off the top of my head, will need to look at this again but most likely it can be optimised

e) That code was once upon a time from an Adafruit library, though we do not use the interrupts as one some irons they do not work (not soldered correctly).

The highpass was turned on to be used for activity detection, with orientation based on its internal orientation engine. It has long been intended to change all of the accelerometers to not do internal filtering and perform the display orientation detection in code but no one (mostly me) has bothered to code it. If you would like to share, I'm sure it would be adopted with open arms ❤️ But also this is something that should be done long term at some point.

f) Handle all ADC sampling in one place only This I 100% agree with and will work to have done, its a quite logical optimisation that is long overdue.

Honestly it sounds like you have done a fantastic job of re-writing software for these devices, if you would like to contribute anything back to this software that would be fantastic, or even open source your software so that others could use it / community could share resources and ideas back and forth. Obviously there is no pressure to do this though; this is just a tiny project in the corner of the internet :) This project does need some love and a little life in innovations, so anything you would want to release would be excellent to see, though no pressure. There has been a lot of hands in this codebase over the years and some things have evolved more than others. It is probably worth doing a re-evaluation from the ground up of some of the code that has been around for ~5 years.

Definitely appreciate the effort in writing this up for the community, and will be back soon (i hope) with some changes based on this, I think you are absolutely correct on these and integrating some or all of these will take time but should be worth it.

[discip]

@sandmanRO Good Morning, It seems that you have done your homework prior to having posted this and consequential you have a pretty good idea of ​​what you've written about. Very promising at first. Kudos! 😲 Still, it would be nicer if you talked more respectfully about the work of others.

Your work will prove to be good on its own if it works on other TS100s as well.

On the other hand, you did a great job posting this.

Especially this part made me prick up my ears:

You guys do that and you will be amazed how stable everything becomes (so stable that several times during development I though the STM32 just hanged on me...nope...only scary stable readings)

Because there were discussions in the past about the temp readings being all over the place.

The graphic mode got my attention as well.

And maybe the code for the TS80 & TS80P could be improved with your knowledge as well. 😃

Looking forward to the next chapter. 😁

@Ralim Kudos for staying objective!

@sandmanRO & @Ralim

It would be exciting witnessing a collaboration between the two of you.

[Ralim]

@discip I agree with the comment on the tone; this very much comes across exceptionally confronting which is not what I hope the author intended. I took a fair break after reading this the first time before I wrote the response.

Honestly, all of these changes here sound like exactly the sort of tweaks and changes I would love to be able to pull in to improve the state of things for everyone. I wasn't surprised that there were bugs in the setup of the DAQ code, some of this code goes back to when I was first using STM's and hasn't ever really been touched since then.

If the code for this was open sourced or even chunks of it posted here or as a PR It would be greatly accepted and integrated.

Would be huge appreciation for graphical improvements given that some people really love flashy GUI's :)

That said, guessing by the screenshot this code is not based off IronOS, so assuming as such PR's are unlikely.

That said, the writeup is highly appreciated, have always wanted someone to audit this code and I think I finally have that 🙃

For the first point I'm not 100% certain the code is exactly wrong as the TRGO output is not being used, but rather the direct link from T2 CC1 to the ADC, and the CC1 event is triggered on match, ignoring the polarity of the PWM configuration. I've done a little bit of testing around this and I feel that the current setup is valid albeit not well documented with the ADC being set directly to the CC1 signal rather than the TRGO output.

My validation for thus was to move the ADC sample time well into the PWM driver area (pull it back into the "power" area) and test both methods, and both methods resulting in similar disturbances depending on where the value for channel 1 of timer 2 is set to. Noting sample size here is only two units as thats all I have on me at the moment. Could be something else going widly wrong 😁 Did also disable the fast/slow PWM code to make this a fair test. That said, this testing has shown that we could easily have a longer adc sampling time, so I probably need to dig into why it is so short. I think it was done to keep short the settling time to the ADC cap was quite fast with the nearly direct drive of the op-amp, but might need to get out the scope or datasheets to validate that.

Though I do think your setup is more logical of a way of going about it though, so inclined to change to it anyway just since it is far more clear of a setup.

Would be curious to see the actual setup you are using on the timer to have these scary stable readings, if you are willing to share of course.

Testing just one injected channel seems to perform about the same as the pair, though not particularly noiser than the other from what I've seen and I do like the idea of moving the power sampling to be in sync in the ADC2 injected time slot. I'll have to do the maths about the sampling time, the 8pF internal capacitance is quite small in the stm32; but also this will heavily depend on the speed of your ADC :)

I agree the fast and slow pwm is a bit odd, I believe the authors intent was that it preserves the same delay+sample time, even with the speed change. As this part should be fairly constant, rather than having just a change of the divider, as this would effectively half (or double; your choice) this time period the ADC is sampling in.

Anyways, definitely some good food for thought in this; and also a huge thankyou for your interest in the first place :)

[sandmanRO]

Hello Gentlemen, English is not my first language (that I suppose is obvious) so please don't take my bluntness as lack of respect. I took the time to write down my findings and that by itself is anything but lack of respect for your work. Few questions have been raised. I will address them. First the use of the same channels on dual mode. stm32s-adc-modes-and-their-applications-stmicroelectronics.pdf Please refer to the page 9/18 (top of the page, Dual Mode, Note)

[paulfertser]

On Wed, Sep 08, 2021 at 03:22:11AM -0700, Ben V. Brown wrote:

I agree the fast and slow pwm is a bit odd, I believe the authors intent was that it preserves the same delay+sample time, even with the speed change. As this part should be fairly constant, rather than having just a change of the divider, as this would effectively half (or double; your choice) this time period the ADC is sampling in.

I do not remember it clearly by now but it feels like your description is pretty accurate. Guess the idea was that we want to spend as little time as possible on ADC (when going full power), and your code ("slow PWM) was already doing that, so using higher PWM frequency when lower power was asked for requires changing the ADC times as it's expressed in PWM clock ticks or else we would be trying to measure too fast for the hardware.

-- Be free, use free (http://www.gnu.org/philosophy/free-sw.html) software! @.***

[sandmanRO]

As my code is fairly different I will right down some snippets of code that would follow the naming used with your code (if/when possible) so it could integrated with yours with minimum effort if you decide to do so. I should have them in a couple of days or so. I hope it's ok if I will attach them as zip file here.

[Ralim]

Hello Gentlemen, English is not my first language (that I suppose is obvious) so please don't take my bluntness as lack of respect. I took the time to write down my findings and that by itself is anything but lack of respect for your work.

No problem, honestly your English is good enough that it isnt super obvious its not your first language. Out of curiosity, what is your native language? (As a sad single language user I find it super interesting to hear about)

Few questions have been raised. I will address them. First the use of the same channels on dual mode. stm32s-adc-modes-and-their-applications-stmicroelectronics.pdf Please refer to the page 9/18 (top of the page, Dual Mode, Note)

Ouch, yep I never saw that note. I've not really noticed the impact of this but definitely will get a patch to work around this; will follow your suggestion to sample vin at the same time.

As my code is fairly different I will right down some snippets of code that would follow the naming used with your code (if/when possible) so it could integrated with yours with minimum effort if you decide to do so. I should have them in a couple of days or so. I hope it's ok if I will attach them as zip file here.

Honestly, so long as the code is readable in English (or near enough, online translators get me quite far) to figure out intent, dont stress too much about restructure, I've worked with some terrible things, I'm sure your code is perfectly understandable.

Attaching a zip is completely fine, anything you are willing to share I would love to be able to see, and integrate what can be integrated :)

[sandmanRO]

As for the 'precise' time when the injected ADC is triggered you could try this. Get the ticks from TIM2 CTR1 Period Complete and compare them with the ticks right after the PID triggered. If the injected channels starts on TIM2 CTR1 Pulse Complete the difference should be at least the equivalent TIM2 CTR1 pulse width. Otherwise (and you will notice that) if the difference is like 0-1 ticks then the injected ADC is triggered by TIM2 CTR1 Period Complete and not by pulse complete as intended. The PID loop wakes up triggered by injected ADC conversion complete interrupt so measuring the time from PID loop would give us a fairly accurate (within 1 tick) time when the injected ADC is triggered.

[discip]

@sandmanRO & @Ralim

As I assumed, your getting along quite well already. 😁

Can't wait to see the results of this teamwork of yours!

[sandmanRO]

Sorry I missed that question, possibly others. I'm Romanian. For the past 15 years I've been running a small business in the field of data acquisition (www.roscientific.com). Before that I was employed as software engineer for the top dog in the field. That would be National Instruments. However, I'm a programmer by trade. My actual background is physics. Nevertheless, it turns out that having a decent physics background is a good assed in this business as it allows to interface with customers from various engineering fields...and that would be about me. Returning to the issue, if a full code overhaul is not critical then I could add relevant snippets of code (with minimum variable naming changes) in plain text. I would start with the very core of my PID loop.

[sandmanRO]

// Sandman note: //////////////////////////////////////////////////////////////////////////////////////////////////////////
//                                                                                      //
// PID Challenge - we have a small thermal mass that we to want heat up as fast as possible but we don't    //
// want to overshot excessively (if at all) the setpoint temperature. In the same time we have 'imprecise'          //
// instant temperature measurements. The nature of temperature reading imprecision is not necessarily       //
// related to the sensor (thermocouple) or DAQ system, that otherwise are fairly decent. The real issue is  //
// the thermal inertia. We basically read the temperature in the window between two heating sessions when   //
// the output is off. However, the heater temperature does not dissipate instantly into the tip mass so     //
// at any moment right after heating, the thermocouple would sense a temperature significantly higher than  //
// moments later. We could use longer delays but that would slow the PID loop and that would lead to other  //
// negative side effects. As a result, we can only rely on the I term but with a twist. Instead of a simple //
// integrator we are going to use a self decaying integrator that acts more like a dual I term / P term     //
// rather than a plain I term. Depending on the circumstances, like when the delta temperature is large,    //
// it acts more like a P term whereas on closing to setpoint it acts increasingly closer to a plain I term. //
// So in a sense, we have a bit of both.                                                        //
//                                                                       So there we go...
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

        // Setpoint delta
        setpointDelta = pidSetpoint - tipTemperature;

        // P = (Thermal Mass) x (Delta Temperature / T_FACTOR) / 1sec, where thermal mass is in X10 J / °C and
        // delta temperature is in T_FACTOR x °C. The result is the power in X10 W needed to raise (or decrease!) the
        // tip temperature with (Delta Temperature / T_FACTOR) °C in 1 second.
        // Note on powerStore. On update, if the value is provided in X10 (W) units then inertia shall be provided
        // in X10 (J / °C) units as well. Also, powerStore is updated with a gain of 2. Where this comes from: The actual
        // power CMOS is controlled by TIM3->CTR1 (that is software modulated - on/off - by TIM2-CTR4 interrupts). However,
        // TIM3->CTR1 is configured with a duty cycle of 50% so, in real, we get only 50% of the presumed power output
        // so we basically double the need (gain = 2) to get what we want.
        powerOut = powerStore.update(HW_TIP_THERMAL_MASS * setpointDelta / T_FACTOR,     // the required power
                                     HW_TIP_THERMAL_MASS,                       // inertia factor
                                     2,                                         // gain
                                     Board::getPwmCycleRate(),                      // PID cycle frequency
                                     powerLimit);                                   // power limit

[sandmanRO]

The powerStore is based on this template:

template <class T = int32_t> struct Integrator
{
    T sum;

    T update(const T val, const int32_t inertia, const int32_t gain, const int32_t rate, const int32_t limit)
    {
        // Decay the old value. This is a simplified formula that still works with decent results
        // Ideally we would have used an exponential decay but the computational effort required
        // by exp function is just not justified here in respect to the outcome
        sum = sum * (100 - inertia / rate) / 100;
        // Add the new value x integration interval ( 1 / rate)
        sum += gain * val / rate;

        // limit the output
        if (sum > limit)
            sum = limit;
        else if (sum < -limit)
            sum = -limit;

        return sum;
    }

    void set(T const val) { sum = val; }

    T get(bool positiveOnly = true) const { return (positiveOnly) ? ((sum > 0) ? sum : 0) : sum; }
};

[sandmanRO]

I keep all the internal temperature related variables in Celsius multiplied by T_FACTOR (this is 9000). This way we can switch back and forth between C and F units without changing the actual internal value.

[sandmanRO]

the powerLimit is minimum between the hardware limit (with TS100 this would be 65W) and the user specified limit

[sandmanRO]

getPwmCycleRate() would return the actual frequency (in Hz) of the PWM cycle (in my case this switches between 5Hz and 10Hz only, depending on the conditions)

[sandmanRO]

Now let's go the configurations for ADCs and TIMs

[sandmanRO]

This is ADC1. The regular ADC1 reads the handle temperature, injected ADC1 reads tip thermocouple

static void ADC1_Init(void) { ADC_MultiModeTypeDef multimode; ADC_ChannelConfTypeDef sConfigRegular; ADC_InjectionConfTypeDef sConfigInjected;

hadc1.Instance = ADC1;
hadc1.Init.ScanConvMode = ADC_SCAN_ENABLE;
hadc1.Init.ContinuousConvMode = ENABLE;
hadc1.Init.DiscontinuousConvMode = DISABLE;
hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc1.Init.NbrOfConversion = ADC_CONVERSIONS;
HAL_ADC_Init(&hadc1);

sConfigRegular.SamplingTime = ADC_SAMPLETIME_28CYCLES_5;
sConfigRegular.Channel = TMP36_ADC1_CHANNEL;
sConfigRegular.Rank = ADC_REGULAR_RANK_1;
HAL_ADC_ConfigChannel(&hadc1, &sConfigRegular);
sConfigRegular.Rank = ADC_REGULAR_RANK_2;
HAL_ADC_ConfigChannel(&hadc1, &sConfigRegular);
sConfigRegular.Rank = ADC_REGULAR_RANK_3;
HAL_ADC_ConfigChannel(&hadc1, &sConfigRegular);
sConfigRegular.Rank = ADC_REGULAR_RANK_4;
HAL_ADC_ConfigChannel(&hadc1, &sConfigRegular);

sConfigInjected.InjectedChannel = TIP_TEMP_ADC1_CHANNEL;
sConfigInjected.InjectedNbrOfConversion = ADC_CONVERSIONS;
sConfigInjected.InjectedSamplingTime = ADC_SAMPLETIME_28CYCLES_5;
sConfigInjected.ExternalTrigInjecConv = ADC_EXTERNALTRIGINJECCONV_T2_CC1;
sConfigInjected.AutoInjectedConv = DISABLE;
sConfigInjected.InjectedDiscontinuousConvMode = DISABLE;
sConfigInjected.InjectedOffset = 0;

sConfigInjected.InjectedRank = ADC_INJECTED_RANK_1;
HAL_ADCEx_InjectedConfigChannel(&hadc1, &sConfigInjected);
sConfigInjected.InjectedRank = ADC_INJECTED_RANK_2;
HAL_ADCEx_InjectedConfigChannel(&hadc1, &sConfigInjected);
sConfigInjected.InjectedRank = ADC_INJECTED_RANK_3;
HAL_ADCEx_InjectedConfigChannel(&hadc1, &sConfigInjected);
sConfigInjected.InjectedRank = ADC_INJECTED_RANK_4;
HAL_ADCEx_InjectedConfigChannel(&hadc1, &sConfigInjected);

multimode.Mode = ADC_DUALMODE_REGSIMULT_INJECSIMULT;
HAL_ADCEx_MultiModeConfigChannel(&hadc1, &multimode);

    while (HAL_ADCEx_Calibration_Start(&hadc1) != HAL_OK);

}

[sandmanRO]

This is ADC2. Only injected for reading the voltage input

static void ADC2_Init(void) { ADC_InjectionConfTypeDef sConfigInjected;

hadc2.Instance = ADC2;
hadc2.Init.ScanConvMode = ADC_SCAN_ENABLE;
hadc2.Init.ContinuousConvMode = ENABLE;
hadc2.Init.DiscontinuousConvMode = DISABLE;
hadc2.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc2.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc2.Init.NbrOfConversion = ADC_CONVERSIONS;
HAL_ADC_Init(&hadc2);

sConfigInjected.InjectedChannel = VIN_ADC2_CHANNEL;
sConfigInjected.InjectedNbrOfConversion = ADC_CONVERSIONS;
sConfigInjected.InjectedSamplingTime = ADC_SAMPLETIME_28CYCLES_5;
sConfigInjected.ExternalTrigInjecConv = ADC_EXTERNALTRIGINJECCONV_T2_CC1;
sConfigInjected.AutoInjectedConv = DISABLE;
sConfigInjected.InjectedDiscontinuousConvMode = DISABLE;
sConfigInjected.InjectedOffset = 0;

sConfigInjected.InjectedRank = ADC_INJECTED_RANK_1;
HAL_ADCEx_InjectedConfigChannel(&hadc2, &sConfigInjected);
sConfigInjected.InjectedRank = ADC_INJECTED_RANK_2;
HAL_ADCEx_InjectedConfigChannel(&hadc2, &sConfigInjected);
sConfigInjected.InjectedRank = ADC_INJECTED_RANK_3;
HAL_ADCEx_InjectedConfigChannel(&hadc2, &sConfigInjected);
sConfigInjected.InjectedRank = ADC_INJECTED_RANK_4;
HAL_ADCEx_InjectedConfigChannel(&hadc2, &sConfigInjected);

while (HAL_ADCEx_Calibration_Start(&hadc2) != HAL_OK);

}

[sandmanRO]

This is TIM2

static void TIM2_Init(void) { TIM_ClockConfigTypeDef sClockSourceConfig; TIM_MasterConfigTypeDef sMasterConfig; TIM_OC_InitTypeDef sConfigOC;

htim2.Instance = TIM2;
htim2.Init.Prescaler = 8000; // 8 MHz timer clock / 2000 = 1 kHz tick rate

htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
htim2.Init.Period = TIM_PERIOD;                     // 200-1
htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV4;
htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
htim2.Init.RepetitionCounter = 0;
HAL_TIM_Base_Init(&htim2);

sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig);

HAL_TIM_PWM_Init(&htim2);
HAL_TIM_OC_Init(&htim2);

sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig);

sConfigOC.OCMode = TIM_OCMODE_PWM1;
sConfigOC.OCFastMode = TIM_OCFAST_ENABLE;
sConfigOC.OCPolarity = TIM_OCPOLARITY_LOW;
sConfigOC.Pulse = 180;
HAL_TIM_PWM_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_1);
sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
sConfigOC.Pulse = 0;
HAL_TIM_OC_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_4);

HAL_TIM_Base_Start_IT(&htim2);
HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_1);
HAL_TIM_PWM_Start_IT(&htim2, TIM_CHANNEL_4); //Channel 4 start w/ interrupts
HAL_NVIC_SetPriority(TIM2_IRQn, 15, 0);
HAL_NVIC_EnableIRQ(TIM2_IRQn);

}

[sandmanRO]

static void TIM3_Init(void) { TIM_ClockConfigTypeDef sClockSourceConfig; TIM_MasterConfigTypeDef sMasterConfig; TIM_OC_InitTypeDef sConfigOC;

htim3.Instance = TIM3;
htim3.Init.Prescaler = 8;                                       
htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
htim3.Init.Period = 100;    
htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV4;
htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
HAL_TIM_Base_Init(&htim3);
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig);

HAL_TIM_PWM_Init(&htim3);

HAL_TIM_OC_Init(&htim3);

sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig);

sConfigOC.OCMode = TIM_OCMODE_PWM1;
sConfigOC.Pulse = 50;
sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
sConfigOC.OCFastMode = TIM_OCFAST_ENABLE;
HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, PWM_Out_CHANNEL);

}

[discip]

@sandmanRO

Man you are fast! 🤯

I hope @Ralim is able to keep up. 😁

[sandmanRO]

And this is the master init sequence:

HAL_ADCEx_MultiModeStart_DMA(&hadc1, ADCBuffer, ADC_SAMPLES); HAL_ADCEx_InjectedStart(&hadc2); HAL_ADCEx_InjectedStart_IT(&hadc1);

[sandmanRO]

And now the actual data grabbing:

// Start of ADC Section ***

// getTipADC returns the average value or 'instant' value. Upon 'sample' flag set, the function grabs a new sample
// from the ADC1 injected channel, updates the filter with it and returns the latest value. This is slightly different than
// what we do on VIN and handle. However, to work properly, the PID relies on a fast temperature feedback.
uint16_t Board::getTipADC(bool sample)
{
    static bool firstCall = true;
    static AverageFilter<uint16_t, ADC_SAMPLES> adcFilter = {{0}, 0, 0};
    if (sample || firstCall)
    {
        // for consistency we should call for samples in one single place like from the PID loop
        // as the only place we are synchronized with ADC injected channels (the channels that read tip temperature)
        // all other calls to getTipADC() should have sample parameter set to false and retrieve the averaged data instead
        uint16_t latestADC = 0;

        latestADC += hadc1.Instance->JDR1;
        latestADC += hadc1.Instance->JDR2;
        latestADC += hadc1.Instance->JDR3;
        latestADC += hadc1.Instance->JDR4;

        // X4 ADC - 4 x 12bit readings

        if (firstCall)
        {
            for (uint8_t i = 0; i < ADC_SAMPLES; i++)
                adcFilter.update(latestADC);
            firstCall = false;
        }
        else
        {
            adcFilter.update(latestADC);
        }
        return latestADC;
    }
    return adcFilter.average();
}

// getVinADC always returns the average value. The 'sample' flag just tells the function
// to grab a new sample from the ADC2 injected channel and update the filter with it.
static uint16_t getVinADC(bool sample)
{
    static bool firstCall = true;
    static AverageFilter<uint16_t, ADC_SAMPLES> adcFilter = {{0}, 0, 0};
    if (sample || firstCall)
    {
        // for consistency we should call for samples in one single place like from the PID loop
        // as the only place we are synchronized with ADC injected channels (the channels that read tip temperature)
        // all other calls to getTipADC() should have sample parameter set to false and retrieve the averaged data instead
        uint16_t latestADC = 0;

        latestADC += hadc2.Instance->JDR1;
        latestADC += hadc2.Instance->JDR2;
        latestADC += hadc2.Instance->JDR3;
        latestADC += hadc2.Instance->JDR4;

        // X4 ADC - 4 x 12bit readings

        if (firstCall)
        {
            for (uint8_t i = 0; i < ADC_SAMPLES; i++)
                adcFilter.update(latestADC);
            firstCall = false;
        }
        else
        {
            adcFilter.update(latestADC);
        }
    }
    return adcFilter.average();
}

// getHandleADC always returns the sum value. The 'sample' flag just tells the function
// to sum up the samples from the regular ADC1 buffer. No extra buffer required as this function
// relies on DMA filled ADC buffer
static uint16_t getHandleADC(bool sample)
{
    static bool firstCall = true;
    static uint32_t adcFilter = 0;
    if (sample || firstCall)
    {
        adcFilter = 0;
        for (uint8_t i = 0; i < ADC_SAMPLES; i++)
            adcFilter += ADCBuffer[i];
        firstCall = false;
    }
    return adcFilter; // X16 (ADC_SAMPLES)
}

[sandmanRO]

Now how do I set the PWM (the call is made from PID loop and the power is the powerOut as seen above). getPwmCycleTicks() would always return 199 as I'm using a fixed PWM cycle period.

void TipWorks::setOutput(int32_t power)
{
    uint32_t pwm = 0;
    if (power > 0)
    {
        pwm = (uint32_t)Board::getPwmCycleTicks() * (uint32_t)power / Board::getAvailablePowerX10();
        Board::selectPWMMode(pwm);      // set the best pwm settings
    }
    Board::setTipPWM((uint8_t)pwm);
}

[sandmanRO]

And this is the full PWM handling

// Start of PWM Section **************************************************************************************************

void Board::setTipPWM(uint8_t pwm)
{
    pwmSafetyTimer = SAFETY_RESET;  
    if (pwm > pwmPowerTicksLimit)   // Constrain the pwm to the current pwm power ticks limit
        pwm = pwmPowerTicksLimit;
    if (pwmPowerTicks != pwm)
    {
        pwmPowerTicks = pwm;
        pwmPowerChanged = true;
    }
}

static void switchToFastPWM(void)
{
    //////////////////////////////////////////////////////////////////////////////////////////////
    // htim2.Instance->ARR  = pwmCycleTicks (200-1) counts @ 2kHz tick rate = 10Hz cycle rate   //
    // It is set in TIM2_Init() function - see htim2.Init.Period initialization in Setup.c  //
    //////////////////////////////////////////////////////////////////////////////////////////////
    pwmPowerTicksLimit  = pwmCycleTicks - 2 * pwmBaseWaitTicks - 2 * pwmBaseDaqTicks;
    pwmTrigInjTicks     = pwmCycleTicks - 2 * pwmBaseDaqTicks;
    pwmPrescaler        = 4000; // 8 MHz internal clock / 4000 prescaler = 2kHz tick rate
    pwmCycleRate        = 10;   // PWM cycle rate in Hz
    fastPWM             = true;
    pwmRateChanged      = true;
}

static void switchToSlowPWM(void)
{
    //////////////////////////////////////////////////////////////////////////////////////////////
    // htim2.Instance->ARR  = pwmCycleTicks (200-1) counts @ 1kHz tick rate =  5Hz cycle rate   //
    // It is set in TIM2_Init() function - see htim2.Init.Period initialization in Setup.c  //
    //////////////////////////////////////////////////////////////////////////////////////////////
    pwmPowerTicksLimit  = pwmCycleTicks - 1 * pwmBaseWaitTicks - 1 * pwmBaseDaqTicks;
    pwmTrigInjTicks     = pwmCycleTicks - 1 * pwmBaseDaqTicks;
    pwmPrescaler        = 8000; // 8 MHz internal clock / 8000 prescaler = 1kHz tick rate
    pwmCycleRate        = 5;    // pwm cycle rate in Hz
    fastPWM             = false;
    pwmRateChanged      = true;
}

void Board::selectPWMMode(uint32_t pwm)
{
    if (fastPWM && pwm  > pwmPowerTicksLimit) 
    {                                           
        switchToSlowPWM();                      
    }
    else if (!fastPWM && (pwm + pwmBaseWaitTicks + pwmBaseDaqTicks) < (pwmPowerTicksLimit / 2))
    {                                           
        switchToFastPWM();                      
    }                                           
}                                               

uint16_t Board::getPwmCycleRate(void) { return pwmCycleRate; }

uint8_t Board::getPwmCycleTicks(void) { return pwmCycleTicks; }

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
    if (htim->Instance == TIM2)                         
    {
        if (pwmRateChanged)
        {
            htim2.Instance->PSC     = pwmPrescaler;     // set TIM2 prescaler at 8 MHz / PWM Tick Rate
            htim2.Instance->CCR1    = pwmTrigInjTicks;  // set TIM2 CTR1 trigger pulse width (Power + Wait ticks)
            pwmRateChanged          = false;
        }
        if (pwmPowerChanged)
        {
            htim2.Instance->CCR4    = pwmPowerTicks;    // set TIM2 CTR4 power pulse width (Power ticks)
            pwmPowerChanged         = false;
        }
        if (pwmSafetyTimer > 0)
        {
            pwmSafetyTimer--;
        }
        else
        {
            pwmPowerTicks = 0;
        }
        if (htim2.Instance->CCR4 && pwmSafetyTimer)
        {
            HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_1);   // TIM2 CH4 pulse is up - turn on the actual power output
        }
        else
        {
            HAL_TIM_PWM_Stop(&htim3, TIM_CHANNEL_1);
        }
    }
    else if (htim->Instance == TIM1)
    {
        HAL_IncTick();                                  // STM timebase counter (every 1ms)
    }
}

void HAL_TIM_PWM_PulseFinishedCallback(TIM_HandleTypeDef *htim)
{
    if (htim->Channel == HAL_TIM_ACTIVE_CHANNEL_4)
    {
        HAL_TIM_PWM_Stop(&htim3, TIM_CHANNEL_1);        // TIM2 CH4 pulse done - turn off the actual power output
    }
}

// End of PWM Section ****************************************************************************************************

[sandmanRO]

This should cover pretty much everything. Maybe just a small note on the PWM switch: in real terms, I switch from slow PWM to fast PWM only when the ON time in slow PWM cycle is less than the actual ON time in fast PWM cycle. As the tick rate in slow PWM is half the rate of fast PWM we divide pwmPowerTicksLimit by 2. The added (pwmBaseWaitTicks + pwmBaseDaqTicks) works as hysteresis. These are constants used: static const uint8_t pwmCycleTicks = TIM_PERIOD; //200-1 static const uint8_t pwmBaseWaitTicks = 10; static const uint8_t pwmBaseDaqTicks = 10;

[sandmanRO]

Now about movement:

//********** LIS2DH12 Registers **************************

#define LIS2DH_I2C_ADDRESS (25 << 1)

#define LIS_CTRL_REG1     0x20 | 0x80
#define LIS_CTRL_REG2     0x21 | 0x80
#define LIS_CTRL_REG3     0x22 | 0x80
#define LIS_CTRL_REG4     0x23 | 0x80
#define LIS_CTRL_REG5     0x24 | 0x80
#define LIS_CTRL_REG6     0x25 | 0x80

#define LIS_OUT_X_L       0x28 | 0x80
#define LIS_OUT_X_H       0x29 | 0x80
#define LIS_OUT_Y_L       0x2A | 0x80
#define LIS_OUT_Y_H       0x2B | 0x80
#define LIS_OUT_Z_L       0x2C | 0x80
#define LIS_OUT_Z_H       0x2D | 0x80

#define LIS_INT1_CFG      0x30 | 0x80
#define LIS_INT1_SRC      0x31 | 0x80
#define LIS_INT1_THS      0x32 | 0x80
#define LIS_INT1_DURATION 0x33 | 0x80

#define LIS_INT2_CFG      0x34 | 0x80
#define LIS_INT2_SRC      0x35 | 0x80
#define LIS_INT2_THS      0x36 | 0x80
#define LIS_INT2_DURATION 0x37 | 0x80

//********** End of LIS2DH12 Registers *****************

static const I2C::I2C_REG config[] =  {{LIS_CTRL_REG1, 0b00110111, 0},  // 25Hz, enable X,Y,Z Axes
                {LIS_CTRL_REG2, 0b00000000, 0}, // High-pass filter off
                {LIS_CTRL_REG3, 0b01100000, 0}, // Set INT1 interrupt
                {LIS_CTRL_REG4, 0b10001000, 0}, // BDU on, HR on
                {LIS_CTRL_REG5, 0b00001100, 0}, // INT1 Latched 4D (Movement Detection - see INT1_CFG)
                {LIS_CTRL_REG6, 0b00000010, 0}, // Set INT_POLARITY
                {LIS_INT1_THS, 0x10, 0},    // about +/-10 deg threshold
                {LIS_INT1_DURATION, 10, 0}, // count in ticks of (1/25Hz)
                {LIS_INT1_CFG, 0b01111111, 0}}; // INT1 Movement Detection 6D (turned into 4D - see CTRL_REG4)

int32_t LIS2DH12::threshold = 0;

int16_t LIS2DH12::sensorData[3] = {0};

bool    LIS2DH12::detect() { return I2C::probe(LIS2DH_I2C_ADDRESS); }

bool    LIS2DH12::initalize() { return I2C::writeRegistersBulk(LIS2DH_I2C_ADDRESS, config, sizeof(config) / sizeof(config[0])); }

void    LIS2DH12::getData(int16_t &x, int16_t &y, int16_t &z, Orientation &orientation)
{
    I2C::read(LIS2DH_I2C_ADDRESS, LIS_OUT_X_L, reinterpret_cast<uint8_t *>(sensorData), 3 * sizeof(int16_t));
    x = sensorData[0];
    y = sensorData[1];
    z = sensorData[2];

    // The LIS2DH12 movement / positioning detection is actually kind of lame. It fails (by design I suppose)
    // to produce event data if more than one axes exceed the threshold. This might be ok for devices
    // that move / rotate strictly on one axis at a time but never on multiple axis simultaneously. As of result, we need
    // to handle the real world scenarios in "software", see below the switch default handling.
    // Note on auto-orientation: in practice, when working, the iron tip (that matches the accelerometer's X Axis) is oriented
    // downwards. I found it quite common that while you keep the pen like soldering iron in your hand, the Y accelerometer axis
    // to be oriented to a direction that otherwise at iron horizontal position would trigger a display orientation change. For
    // example you are left handed. When you start working you will find that the tendency is to rotate the iron (especially if
    // you are left handed, the left handed guys know what I'm talking about) on it's axis in such a way it would trigger an
    // orientation as for right handed use. This unintentional orientation switch is undesirable. To avoid this, the implementation
    // does this: the more the X axis is oriented downwards the more you  need to incline the iron on Y axis to trigger an orientation
    // change. If for example, when the iron is in horizontal position it's enough to rotate on "sides" (Y direction) about 10 degrees
    // to trigger an orientation change, when the iron is pointed downwards at 45 degrees you would need to rotate on sides as much as
    // 60 degrees to get an orientation switch. You really need to twist your hand to do that while you hold the iron in your hand like
    // a pen so definitely this would not be unintentional.
    switch (I2C::read(LIS2DH_I2C_ADDRESS, LIS_INT1_SRC) & 0b00001100)
    {
    case 4:
        orientation = ORIENTATION_LEFT;
        break;
    case 8:
        orientation = ORIENTATION_RIGHT;
        break;
    default:
        threshold = 3000;   // 3000 represents axis acceleration due to Earth gravity at about 10.5 degrees axis inclination from horizontal
        if (x < (-threshold))                   // iron tip oriented downwards
        {
            threshold -= 6 * (int32_t)x / 5; 
        }
        if (y < (-threshold))
            orientation = ORIENTATION_LEFT;
        else if (y > threshold)
            orientation = ORIENTATION_RIGHT;
        else
            orientation = ORIENTATION_FLAT;
        break;
    }
}

[sandmanRO]

And this is how the orientation returned by LIS chipset is handled:

if (settings.displayOrientation == ORIENTATION_AUTO && orientation != ORIENTATION_FLAT)
{
    // Calculate a "simplified" standard deviation - would still give a good indication
    // of the data spread in the collection. A small std indicates static (Earth gravity)
    // acceleration values and not as a result of a movement. For rotation purposes
    // we want to rely on static values of acceleration only. We don't want the rotation be
    // triggered by sudden movements that would mimic orientation like conditions. 
    // This way we avoid those annoying orientation flickers of the display when the unit is
    // shaken back and forth on certain directions.This imply the acceleration data
    // is not filtered out (high-pass filter is off) in the specific accelerometer configuration
    std = 0;
    for (uint8_t i = 0; i < MOVFILTER; i++)
    {
        std += Utils::Abs(averageX - motionDataX[i]);
        std += Utils::Abs(averageY - motionDataY[i]);
        std += Utils::Abs(averageZ - motionDataZ[i]);
    }
    std /= MOVFILTER;

    if (std < threshold)
    {
        // the actual orientation change will occur first time we
        // refresh the screen - see Display::refresh() function
        pendingOrientation = orientation;
    }
}

[sandmanRO]

Hello paulfertser, The issue does not lie in the way the PWM cycle is segmented. That is absolutely fine. Moreover, changing the PWM cycle parameters is not necessarily bad in itself as long as you keep some tracking of the actual cycle time. The real issue with the current implementation is that there is no real correlation between PWM cycle vs, feedback data & PID output. I mean, obviously there is an arithmetic correlation but not necessarily a sound one. Not sure how to put this so it would be clear: the POWER by itself is an abstract notion...it speaks about the ability of a system to deliver/absorb a certain amount of energy in a certain amount of time. However, what heats up the iron tip is not the "POWER" but the amount of ENERGY we are transferring to the tip (in this particular case the transfer is done by converting electrical energy into thermal energy by resistive effect). We can arithmetically work with POWER but in that case we need to keep in mind that the ENERGY is POWER times TIME. That is, the maximum amount of energy we can transfer to the tip in one cycle is the available power (this is given by the used power supply) times the cycle period. Obviously, the closer you get to the setpoint you might need less than this maximum amount and that is the purpose of the feedback loop, to constantly adjust the demand. The current implementation does not really consider the time aspect. Looking over the comments in the code I see that there is some awareness regarding the issue but nothing implemented consistently. Otherwise, a feedback loop, PID or alike, would get you to the setpoint eventually, even if not set properly, but usually it would either (sometimes severely) overshoot then oscillate up and down setpoint or reach setpoint after longer than necessary time. With the above suggested modifications you will not have such issues disregarding your target is set to 40 or 400 Celsius (and any value in between for that matter) and finally have a TS100 that works as it was meant to. The code could be perfected no doubt but it's the simplest code I could think of, that would still do the job decently.

[Ralim]

@sandmanRO

I've been working through the ADC setup against yours, and a few notes:

• You are using ADC_EXTERNALTRIGINJECCONV_T2_CC1 but for your diagram (and claims) to be true you have to use ADC_EXTERNALTRIGINJECCONV_T2_TRGO and your TIM_TRGO_RESET would have to be TIM_TRGO_OC1REF i believe.

• As it currently stands you are still using the CC1 event the same as IronOS which means that polarity of the CC1 channel does not matter, and this code is not in danger like you claim

• I did some testing around on a few different boards about the issue with sampling the same input in sync with the ADC, this mostly seems to be due to both ADC's sampling at the same time injects noise into the signal. This becomes worse as your input impedance increases. In my testing the ~1k input impedance of each adc dominates this far more than the circuitry in the soldering irons, and thus the noise is exceptionally marginal. And keeping in mind for the oversampling to work some noise is required as well. Though of course this noise is the wrong type, so removing it is good, though wonder what the mix of pro and con with it is.

• That said; in testing I'm not seeing much improvement in precision from the oversampling at the moment (probably as no white noise really), so either going to sampling the external voltage or doing alternate sequenced injected mode would make sense.

• I agree with the idea of sampling the input voltage during the sag event when soldering; so thus I'm going to move ADC2 from sampling the raw measurement to sampling the input voltage.

• I'm wondering (havent looked into yet) about moving the ADC2 trigger to the update event (UEV) of timer2 to capture the input voltage during the heating phase of the cycle (ie start capture at the start of the heat cycle, and use slow sampling times to spread it out). Will do this later on as may take more testing to keep timings sane

• I'm not certain (as you haven't shown it), but you may want to check you have adjusted your ADC samples buffer to account for ADC2 not sampling anything, as you be may be relying on it to read 0 in your current code. I couldn't find a defined behavior for having channels enabled but not configured. Its probably safe but 🤷🏼

Given this, I think the stability you are seeing is mostly a result of just having the better filtering layout in the sampling. By just applying your changes to (wisely) filter the adc readings at the source, and lock sampling time to the PID iterations the values far more stable.

I've refactored to use this wisdom with the sampling and filtered and its now in the refactor-adc branch. Noting I don't actually have a TS100 on hand to test today, only the TS80 and Pinecil.

Going to do this as separate items to keep the changes distinct. So would love it if you could look at the PR here :)

This is just the ADC refactor to handle sampling locked in time with the PID loop.

Then after that will look at fast/slow PWM, and the PID Then finally the accelerometer setup.

[sandmanRO]

Ralim, what the are you talking about? It's exactly the other way around you say it is. ADC_EXTERNALTRIGINJECCONV_T2_CC1 means trigger on Timer2 Capture/Compare 1. In the current setup is occurs on rising edge of TIM2 Ch1. It is true that you can configure it to occur on rising, falling or both edges but the default is rising edge. That is exactly what my diagram, and "claim" said. I have suggested you a simple test. You could try it unless you prefer to revisit STM32 documentation. As for the presumed better filtering, I'm averaging on 4 times less samples than your code does so that statement of yours does not stand either. The stability does not come from better filtering but from the sampling the input voltage at the right time, as stated with my first message. Look, it's not my purpose to convince you guys of anything nor persuade you change your code. You do whatever it feels right with it. I honestly don't care.

[Ralim]

I said that's as in my testing having the timer polarity high or low gave me a trigger time of 283+-1 on my test unit.

I've been testing around and the most stable for me in terms of testing has been to use trgo rather than cc1 directly.

I was asking as I was not seeing the results I would have expected and thus was curious. Could also be this TS80P, it's had its stm32 replaced a few times.

[Ralim]

So, looking at your PID I love how simple it is.

// Sandman note: ////////////////////////////////////////////////////////////////////////////////////////////////////////// // // // PID Challenge - we have a small thermal mass that we to want heat up as fast as possible but we don't // // want to overshot excessively (if at all) the setpoint temperature. In the same time we have 'imprecise' // // instant temperature measurements. The nature of temperature reading imprecision is not necessarily // // related to the sensor (thermocouple) or DAQ system, that otherwise are fairly decent. The real issue is // // the thermal inertia. We basically read the temperature in the window between two heating sessions when // // the output is off. However, the heater temperature does not dissipate instantly into the tip mass so // // at any moment right after heating, the thermocouple would sense a temperature significantly higher than // // moments later. We could use longer delays but that would slow the PID loop and that would lead to other // // negative side effects. As a result, we can only rely on the I term but with a twist. Instead of a simple // // integrator we are going to use a self decaying integrator that acts more like a dual I term / P term // // rather than a plain I term. Depending on the circumstances, like when the delta temperature is large, // // it acts more like a P term whereas on closing to setpoint it acts increasingly closer to a plain I term. // // So in a sense, we have a bit of both. // // So there we go... ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

  // Setpoint delta
  setpointDelta = pidSetpoint - tipTemperature;

  // P = (Thermal Mass) x (Delta Temperature / T_FACTOR) / 1sec, where thermal mass is in X10 J / °C and
  // delta temperature is in T_FACTOR x °C. The result is the power in X10 W needed to raise (or decrease!) the
  // tip temperature with (Delta Temperature / T_FACTOR) °C in 1 second.
  // Note on powerStore. On update, if the value is provided in X10 (W) units then inertia shall be provided
  // in X10 (J / °C) units as well. Also, powerStore is updated with a gain of 2. Where this comes from: The actual
  // power CMOS is controlled by TIM3->CTR1 (that is software modulated - on/off - by TIM2-CTR4 interrupts). However,
  // TIM3->CTR1 is configured with a duty cycle of 50% so, in real, we get only 50% of the presumed power output
  // so we basically double the need (gain = 2) to get what we want.
  powerOut = powerStore.update(HW_TIP_THERMAL_MASS * setpointDelta / T_FACTOR,     // the required power
                               HW_TIP_THERMAL_MASS,                       // inertia factor
                               2,                                         // gain
                               Board::getPwmCycleRate(),                      // PID cycle frequency
                               powerLimit);                                   // power limit

As you probably noticed the output of that timer is AC coupled. In the past I have experimented with different frequencies for that timer to try and drive the signal fast enough to prevent the small off cycles in driving the tip.

I'm wondering if you have done any investigation into this, and if so what your results were? Just wondering, since you were digging through the rest of this code while you wrote your own firmware; if you delved into this :)

( If you have an opinion that is, you dont have to have one 🙃 ).

[Ralim]

In regards to the orientation handling; Given that the LIS is not even the worst accelerometer in use, wondering if its better to just scrap using the internal orientation engine and instead just base it entirely off the x/y/z values (and turn off he high pass filter naturally).

If so, did you find 10.5 degrees was a good number (was it tested for, picked semi-randomly or one you already knew) ?

[sandmanRO]

10 degrees felt right...it would mean something around two thousand nine hundred something counts....so I picked to closest "clean" integer that happened to be 3000...that in real means about 10.5 degrees.

[sandmanRO]

I thought about getting rid of the internal orientation as well. But then again, I spent a whole day traying to make sense of LIS documentation and kind of felt bad about giving up on all that wasted time. Otherwise, there is no real benefit coming out of it. Working with x, y, z accelerations would do just fine.

[Ralim]

I thought about getting rid of the internal orientation as well. But then again, I spent a whole day traying to make sense of LIS documentation and kind of felt bad about giving up on all that wasted time. Otherwise, there is no real benefit coming out of it. Working with x, y, z accelerations would do just fine.

I feel a little better to not be the only one that doesnt like their docs. I'm thinking of dumping the orientation as well... I'll let you know where I get to.

[sandmanRO]

If you fill that a different threshold is right, the math is like this: in +/-2G scale, 1G means about 16384 (that would be Earth acceleration at 90 degrees in respect to the horizontal). For a random alpha angle the threshold would be something like 16384 * sin(alpha).

[sandmanRO]

"feel"

[Ralim]

Yeah unit conversions are fun with the five different accelerometers... They should all be scaled to be similar scale already so will mostly be validation time I fear. Also if you know of a "good" way of doing it other than just checking the gravity vector in the averaged data and masking movement I'm all ears

[sandmanRO]

that simplified "standard deviation" is best way I could think of. It gives an indication on how close the data in the collection is to the average value. A small std means the values are close to the average, which in turn means the acceleration values are static. A large std would imply a large spread of data in respect to the average value, specific to dynamic accelerations.

[sandmanRO]

the true standard deviation would have implied to sum up the squared differences then do the root mean square over the result.

[sandmanRO]

so that "std" could be used to discriminate both movement (if std above a specific threshold) and static (if std below a specific threshold) accelerations. The threshold for static and movement discrimination do not need to be the same.

[sandmanRO]

Most likely there must be a more efficient way doing it but I just could not think of any other right now.

[Ralim]

@sandmanRO Geeze that simpler PID is really nice. Just did the hacky dirty "shove it in there" and it makes a notable difference. (pid branch has the hacky, not quite right code) Will do more work on it when I have more time, but ❤️ .

[sandmanRO]

Well, this is the trade...you will let me use your soldering menu animated icon. That was a stroke of a genius. No matter what I tried, it did not produce the same visually suggestive effect. It would be for internal use only...that is four TS1000 units that I purchased sole for our own needs. Let me stress I'm neither in the business of selling soldering irons nor have any intention of releasing this work to public.

[Firebie]

Hi, Not sure that this is the right place, but why for TS100 we have in 'configuration.h': const int32_t tipMass = 65; // X10 watts to raise 1 deg C in 1 second but for Pinecil const int32_t tipMass = 45; // X10 watts to raise 1 deg C in 1 second although physically tips are the same.

[sandmanRO]

Hello Firebie, I can not speak about Pencil (and honestly my interest does not extend beyond what I'm using, that is TS100) but I have a whole bunch of TS100 tips, various designs. Their thermal mass varies within a range of at least +/-2J/C. 6.5J/C would be a good average value. Using a smaller than real thermal mass would make the PID reach the setpoint slightly slower. Using a largen than real thermal mass would probably make the PID slightly overshoot (especially if the starting temperature is close to the setpoint). However, it's not a critical but rather a guiding value for the PID. Of course, having a spot on value would be ideal but it would imply to know / set precisely the tip you are using. Personally I find this complications unpractical in respect to the outcome, but this is me.

[Ralim]

My view on you using it is that it's fine, since it's both personal use (which main reason I went with the licence was to stop it being "sold", a company is free to use it be default so long as they maintain what it is / release their source).

Also you are keeping the main intent of upstreaming your improvements, so to me it's fine. That said; is love to see your other improvements dumped whenever you have the time if you wished.

@Firebie good question, smells like a bad merge. Going to revisit all of those numbers soon (when time permits) so will rectify that too.

Most likely the old algorithm was miss tuned enough it wasn't noticeable in practical use.

[sandmanRO]

Hello Ralim, Thank you. Much appreciated. We might not be using that icon as one of my younger colleagues came up with this and I did not have the heart to say no to her artwork. Nevertheless, my opinion about your icon stands: simple as possible with maximum effect (the kind of thing that gets me excited about).