Change default pinout

[probonopd]

EDIT: The pinout in this post is outdated. See newer posts below for the recent one.

Continuation from here:

For maximum device compatibliity (including Raspberry Pi 1), we want to have a pinout that needs none of the extra pins introduced with the Raspberry Pi 2.

Since more and more people are building their hardware now, I'd like to propose the new default pinout rather sooner than later.

Should we ever use i2c for the display (easier cabling with fewer wires, potentiometer onboard but ~3 EUR more expensive), then we could even have room for SPI:

What do you think? Feedback appreciated.

Notes:

• 2.2k resistor betweeen LCD pin 1 (VSS) and LCD pin 3 (V0) (10k potentiometer would be better)
• Backlight enabled like this (note the balck and red short wires on the upper left of the green LCD board. K bridged to right side of C2, topmost right side pin of unpopulated chip footprint U3 bridged to the right side of the resistor. CAUTION: Don't blindly do this, measure with a multimeter and understand what you do first! No guarantees.)

MiniDexed_Pinout.zip

[craigyjp]

You still have 4 pins assigned to the LCD on your second diagram, surely those will not be needed if your are using I2c?

[probonopd]

Thanks @craigyjp, updated.

[dcoredump]

I am using I2C displays for my MicroDexed project. In fact, cabling is easier and the I2C versions have a small pot for setting the contrast on the back side.

On the other side you only can define up to 8 or 10 self defined icons. I don't know if this is a library or a hardware limitation, but sometimes more than 8/10 self defined icons are necessary (e.g. for displaying VU-Meter like bars for each TG).

Also you must have in mind that the I2C displays are slower than direct connected ones. This was a problem for me when changing sounds by fast turning an encoder. The display was not fast enough for displaying the sound names. I "fixed" it by using an encoder library which handles fast turns by sending bigger values instead every single step.

Just my two cents...

[probonopd]

Successfully built a unit with the first pinout above (no i2c display for now).

#
# minidexed.ini
#

# Sound device
SoundDevice=i2s
SampleRate=48000
#ChunkSize=256
DACI2CAddress=0
ChannelsSwapped=0

# MIDI
MIDIBaudRate=31250
#MIDIThru=umidi1,ttyS1

# HD44780 LCD
LCDEnabled=1
LCDPinEnable=17
LCDPinRegisterSelect=27
LCDPinReadWrite=0
LCDPinData4=22
LCDPinData5=23
LCDPinData6=24
LCDPinData7=25

# KY-040 Rotary Encoder
EncoderEnabled=1
EncoderPinClock=9
EncoderPinData=10
EncoderPinSwitch=11

# Debug
MIDIDumpEnabled=0
ProfileEnabled=0

If there are no objections, this will become the default soon-ish.

[probonopd]

@rsta2 what should one write in LCDPinReadWrite if LCD pin 5 (RW) is attached to GND directly?

[rsta2]

Set LCDPinReadWrite=0, if RW is directly connected to GND.

[luisfcorreia]

I'm trying this new pinout config, to be able to test it with both RPI1 and RPI2

LCD works well in RPI1, does not with RPI2

(same minidexed.ini configuration on both cards)

[dcoredump]

[...]

If there are no objections, this will become the default soon-ish.

If the pinout is fixed, perhaps someone can create a nice Fritzing pucture showing the wiring?

[probonopd]

Successfully tested the upper (non-i2c) pinout and corresponding configuration on

• RPi 1 Model B Revision 2.0 (512MB) (LCD and encoder work, DAC not tested)
• RPi Zero (DAC, LCD and encoder work)
• RPi 2 (DAC, LCD and encoder work)
• RPi 4 (DAC, LCD and encoder work)

So I'd say we have a winner. The better, they say, is the enemy of the good, so in case we get the display to work with i2c there might be a pinout change again.

[luisfcorreia]

Can you please generate a release for testing?

[diyelectromusic]

It probably isn't massively relevant, and I don't know how far back you want to go with "any version" compatibility, but very early Pi V1 Model B Revision 1 had GPIO 21 in the place where GPIO27 is on V1 B Revision 2 boards onwards...? But if anyone was bothered I'm guessing that as GPIO 4 is free, that could be used instead if it was an issue?

I only mention it for the sake of completeness :)

[probonopd]

According to https://raspberry-projects.com/pi/pi-hardware/raspberry-pi-pcb-versions, I seem to have a Raspberry Pi ("1") Model B Revision 2.0 (512MB) because it says Raspberry Pi (c)2011.12. On this one I tested the new pinout successfully, including display and rotary encoder. Did not tests DAC there.

[luisfcorreia]

According to https://raspberry-projects.com/pi/pi-hardware/raspberry-pi-pcb-versions, I seem to have a Raspberry Pi Model B Revision 2.0 (512MB) because it says Raspberry Pi (c)2011.12. ON this one I tested the new pinout successfully, including display and rotary encoder. Did not tests DAC there.

I have the same board here, will connect additional pins for DAC testing "soon"(TM)

[probonopd]

Can you please generate a release for testing?

https://github.com/probonopd/MiniDexed/suites/6304896074/artifacts/226117903

[diyelectromusic]

I believe that last release has the encoder CLK/DAT pins swapped compared to your original diagram and description - is that correct?

[probonopd]

Don't think so, these are the changes: https://github.com/probonopd/MiniDexed/pull/189/files

Anyway, will be moving LCDPinRegisterSelect from GPIO 27 to GPIO 4 as per your advice now. Then there will be a new round of testing.

[diyelectromusic]

I might be missing something but doesn't that say Clock = 10; Data = 9 compared to the original diagram above where it says Clock = 9; Data = 10? To be honest, C=10;D=9 means the pins are in the same order as my encoder's pins, so that is what I had used on my V1 Pi anyway, but I was just checking that it was correct - that you'd changed them with respect to your original diagram...?

BTW - Would you expect this to work on an I2S DAC connected to the Pi V1 Model B Rev 2's P5 header? That should be supported in the Circle environment, but I don't know if that means it should also work here...?

[luisfcorreia]

these encoders are IMHO wrongly labelled

there is no Clock and Data, just A and B

[diyelectromusic]

BTW - Would you expect this to work on an I2S DAC connected to the Pi V1 Model B Rev 2's P5 header? That should be supported in the Circle environment, but I don't know if that means it should also work here...?

Ignore that - I can tell you it does :) I'm using a V1 Model B Revision 2.0 with a PCM5102 DAC off the P5 header and all works fine with USB MIDI.

[probonopd]

If the encoder pins are reversed, the encoder goes in the wrong direction. Did I mix it up? I think it is wrong in the diagram, will fix in the next iteration.

[probonopd]

Gotta LOVE snap-fit project boxes. I'd be screwing around with screws otherwise all the time and would totally be screwed without them ;-)

[probonopd]

So is this it?

MiniDexed_Pinout.zip

#
# minidexed.ini
#

# Sound device
SoundDevice=i2s
SampleRate=48000
#ChunkSize=256
DACI2CAddress=0
ChannelsSwapped=0

# MIDI
MIDIBaudRate=31250
#MIDIThru=umidi1,ttyS1

# HD44780 LCD
LCDEnabled=1
LCDPinEnable=17
LCDPinRegisterSelect=4
LCDPinReadWrite=0
LCDPinData4=22
LCDPinData5=23
LCDPinData6=24
LCDPinData7=25

# KY-040 Rotary Encoder
EncoderEnabled=1
EncoderPinClock=10
EncoderPinData=9
EncoderPinSwitch=11

# Debug
MIDIDumpEnabled=0
ProfileEnabled=0

[probonopd]

Please test: https://github.com/probonopd/MiniDexed/suites/6306050512/artifacts/226182252

[probonopd]

these encoders are IMHO wrongly labelled there is no Clock and Data, just A and B

Yes, but we use what is printed on the PCB so that people know where to hook it up:

[diyelectromusic]

Please test: https://github.com/probonopd/MiniDexed/suites/6306050512/artifacts/226182252

All works fine on my V1 Model B Rev 2 with USB MIDI, LCD, encoder (both directions/select) with internal PWM and external (via P5) PCM5102.

Kevin.

[diyelectromusic]

[...]

If there are no objections, this will become the default soon-ish.

If the pinout is fixed, perhaps someone can create a nice Fritzing pucture showing the wiring?

I have two here for a V1 and V4 Pi using solderless breadboards and Adafruit "cobblers"? If they are any use you're very welcome to have them: https://diyelectromusic.wordpress.com/2022/04/28/bare-metal-raspberry-pi-minidexed-dx7/

These are using the latest wiring as I understand it (and should be what I've just tested with my other reply today)

Just let me know what to do.

[luisfcorreia]

off-topic, you have a type in your blogpost "For the V4 Pi, I was using my I2S PCM1502 DAC "

[diyelectromusic]

off-topic, you have a type in your blogpost "For the V4 Pi, I was using my I2S PCM1502 DAC "

I keep doing that! Problem with having 1602 and 5102 in the same post! :)

[diyelectromusic]

Please test: https://github.com/probonopd/MiniDexed/suites/6306050512/artifacts/226182252

Also fine on my RPi V4 with external PCM5102 and serial MIDI (both on my Clumsy MIDI interface that has no I2C display). LCD, encoder, audio seem fine.

[probonopd]

Hi @diyelectromusic. Thanks for testing and for your article. Would you mind making a Fritzing diagram of this pinout without a cobbler, just with the bare Raspberry Pi 1, for use in our Wiki?

[diyelectromusic]

Hi @diyelectromusic. Thanks for testing and for your article. Would you mind making a Fritzing diagram of this pinout without a cobbler, just with the bare Raspberry Pi 1, for use in our Wiki?

Yes I can do that. With or without solderless breadboard? i.e. do you just want to show the connections or do you want a practical thing someone could construct (which really needs things pinned into something rather than just "hanging on" by wires)? So it can be more of a "getting started" diagram than an "informational" diagram?

[luisfcorreia]

Hi @diyelectromusic. Thanks for testing and for your article. Would you mind making a Fritzing diagram of this pinout without a cobbler, just with the bare Raspberry Pi 1, for use in our Wiki?

Yes I can do that. With or without solderless breadboard? i.e. do you just want to show the connections or do you want a practical thing someone could construct (which really needs things pinned into something rather than just "hanging on" by wires)? So it can be more of a "getting started" diagram than an "informational" diagram?

I would say, direct connections without any breadboard in between elements

[probonopd]

Yes.

[diyelectromusic]

Ok will do. The only issue that there are three 5V connections required if you include something to control the brightness of the LCD, so some soldering of wires would be required. Adding a solderless breadboard as a breakout means the only soldering is headers, but I'll have a go and see what it looks like!

[probonopd]

Who needs brightness control ;-)

[diyelectromusic]

OK, well there is something like this...?

[Braincell1973]

Just my 2p worth but I built a mt32pi with serial based midi ports and a dac and encoder along with an i2c display........ Wouldn't the best idea to work towards would be an identical pinout so a change of sdcard can swap between mt32pi and minidexed ??

[hizzlekizzle]

I just messed around with this new pinout and found it much, much easier to work with, so cheers for that.

[probonopd]

Thanks @diyelectromusic.

Are you sure the LCD backlight is driven correctly (with a resistor) when attached this way?

Also, the additional resistor or potentiometer for the contrast should be attached to the LCD between V0 and GND.

And please add 2 10nF capacitors between GND on the rotary ancoder module and DT, SW on the rotary encoder module as shown in https://github.com/probonopd/MiniDexed/discussions/178, they increase reliability a lot (fewer missed steps). Thanks @luisfcorreia

[probonopd]

@Braincell1973 mt32pi is using i2c for the display and uses a pinout that doesn't work with the original Raspberry Pi ("1"). If someone would like to use mt32pi hardware with MiniDexed, some manual editing of the pin configuration will be needed as we want to support all Raspberry Pi models by default.

[diyelectromusic]

Are you sure the LCD backlight is driven correctly (with a resistor) when attached this way?

No, so if someone wants to say what they want to use, happy to do that - I had a pot wired in in mine on the breadboard, but took you are your word on "who needs brightness control" and assumed you literally just wanted the connections showing rather than an actual circuit.

One thing though, if lots of components are added it stops being a "wiring diagram" pretty quickly and then in my view ought to go one of two ways: either a) show a physical circuit on a breadboard that someone can actually make (e.g. as a "beginner" getting up and running quickly) or b) show a schematic rather than a Fritzing diagram and let people make their own (as a more experienced person being given guidelines).

I'm not sure "floating components" on a Fritzing diagram really helps people very much as it implies something that can be built like that, but in reality can't...? And the more components are added the more it gets away from a "beginner having a go" - lots of circuitry around an encoder, whilst better in the long run, doesn't get someone up and running quickly...

Happy to do whatever people want, but I think we need to decide who is the audience for the diagram and tailor it accordingly?

[luisfcorreia]

to make things clear:

Contrast is LCD's pin 3 (should be adjustable) Backlight on pins 15 and 16 are Brightness

[probonopd]

Are you sure the LCD backlight is driven correctly (with a resistor) when attached this way?

This is how I was driving my backlight using the resistor that is already on the PCB. Pins 15 and 16 stay unpopulated:

Turns out I was doing it overly complicated: Pin 15 seems to be connected to the anode through the 100 Ohm resistor, too. So your picture is OK, I was just saving 2 cables to the raspberry Pi ;-)

As for contrast, I find that a 2.2k resistor is needed (better: a 10k potentiometer for adjustability):

I'm not sure "floating components" on a Fritzing diagram really helps people very much as it implies something that can be built like that, but in reality can't...?

In fact, soldering to the modules is exactly what I am doing. The only exception being the Raspberry Pi for which I am soldering to such a header so that I don't have to solder to the Raspberry Pi directly:

For the rotary encoder, 2 10nF capacitors on the data lines should be added. They help a lot against "missed steps".

Also, maybe use a Rasperry Pi Zero 2 PCB because I find that one to be the space-price-performance sweet spot for MiniDexed.

Oh, and add the wiring for a PCM5102 DAC module. Updated https://github.com/probonopd/MiniDexed/issues/163#issuecomment-1112696014 above.

If you share your Fritzing files, we can make both schematics and "flying component" wiring diagrams. Thanks a ton!

[diyelectromusic]

In fact, soldering to the modules is exactly what I am doing.

I know - that's what I mean about who is the audience for these - it isn't really someone like you! :)

Ideally I'd add the PCM link and MIDI too, but then that is getting quite a long way away from who I'd imagine the audience would be - someone just wanted to get started and "have a go" with MiniDexed. With a LCD with pre-soldered headers and a KY-040 encoder module and a wiring diagram, almost anyone could try it without any soldering which would be a nice thing to be able to offer.

Anyone capable of soldering extra components probably won't need a Fritzing diagram - they mostly just need the GPIO table, but a recommended schematic would be nice.

If you share your Fritzing files, we can make both schematics and "flying component" wiring diagrams.

I'll see what I can do :)

[diyelectromusic]

Does this one seem any better? I've not added the capacitors, I just can't get it looking clear enough with them in, so they might need to be added as text. It would probably make more sense to solder them directly onto the encoder pcb anyway?

I dropped back to just a single 5V and GND to the LCD (and changed the GND pin used on the PI in the process). It just seems neater that way? What do we think about connections crossing the LCD? I try not to do that, but there are far less crossings doing it this way than not doing it. Alternatively I could move the LCD to the right and drop it down so the connections are all above it, but that is starting to stretch the diagram out a bit and some of the links will be getting quite long...

The main issue is that the wiring makes a lot of sense when wired across the RPi (as if the LCD and encoder are sitting on top like a Hat/Shield) but that isn't so clear in a diagram as everything has to cross the RPi...

Thoughts?

[probonopd]

Yes, I think this is great. Except for the blue connection point on top of the yellow line - this could be misintepreted. I'd do the yellow line more like the orange one, have it to to the left, then to the top, then to the display. Btw, the SCK pin on my i2s module can be left ungrounded and it still works.

And maybe add wires for Serial MIDI in and out? (Not the whole MIDI circuit, just the wires with labels.)

Would you be willing to share the Fritzing file?

[diyelectromusic]

Would you be willing to share the Fritzing file?

Oh yes, sure :) Where do you want it!?

RPi-miniDexed-DefaultPins-Wires.zip

[probonopd]

Cool! If you zip the Fritzing file, then you can attach it to your post above this one. Thank you very much.

[diyelectromusic]

Cool! If you zip the Fritzing file, then you can attach it to your post above this one. Thank you very much.

Try that. There are a couple of things not in the standard library and the pcm5102 is an imported photo, so I don't know if that will include everything or not... give it a go and let me know. Oh, and I've done nothing with the schematic view - that is a mess :)

[diyelectromusic]

Here is an updated Fritzing file, this time with a possibly workable schematic too (seeing as someone was asking elsewhere). There was also two buggy connections in the first one that are now hopefully fixed!

Kevin

RPi-miniDexed-DefaultPins-Wires.zip