Max3155 temperature issue

[overdrive2max]

I am running an SKR 1.3 board with sbc and a max3155 chip for the hotend. The temperature is very stable if I heat the hotend and manually move the printer axis. Turning on the heatbed does not impact on the readings. Once I start a print almost every second temperature reading is 2000c. Sometimes the print will fail due to disconnect being registered. Any advice please?

board.txt leds.diagnostic = NoPin;

//Internal SDCard SPI Frequency. lpc.internalSDCard.spiFrequencyHz = 25000000;

heat.tempSensePins = {bedtemp}; //Max of 3 entries //Soft SPI Temp sensor to use with MAX31865+PT100 softwareSPI.pins = {1.18,1.19,1.20} heat.spiTempSensorCSPins = {1.21, NoPin }; //Max of 2 entries heat.spiTempSensorChannel = 2

//Analogue to Digital prefilter adc.prefilter.enable = true sbc.lpcTfrReadyPin = 1.31

//TMC Smart Drivers stepper.numSmartDrivers = 4; //Adjust to the correct number of smart drivers stepper.TmcDiagPins = { NoPin, NoPin, NoPin, NoPin, NoPin }

config.g M308 S1 P"P1.21" Y"thermocouple-max31855"

[overdrive2max]

I should also note that using a thermistor on the same cable moved to the analog input works without any issue. I have largely shielded the cables from stay voltages and to some extent capacitance that could creep in on anything sensor related.

[gloomyandy]

Hi, Please post all of your config.g file, the output from M122 p200 and the output from M122. Also please post a photo of your board and how you have it set up. How long is the connection to the SBC?

Can you clarify what you mean by "Sometimes the print will fail due to disconnect being registered"? What exactly happens and what error message do you get? Next time you get that error, please post the output from M122 as soon after the error as you can.

It sounds like something during the print is causing the SPI connection to the max3155 to read incorrect results. This could either be a software problem or some sort of hardware problem (noise or possibly a bad connection). Things to try....

1. Try simulating a print job and monitor the temperature during the simulation (this will create a lot of traffic over the SBC connection and we can check if that is causing the problem).
2. Please try manually turning on any software controlled fans and see if they trigger the problem.
3. Please check to see if you see bad readings during home all moves, or if you have a probe during G29 probing.
4. How long are the wires from the SKR board to the max3155?
5. Try creating a test gcode file that only has X/Y moves in it (no heaters and no extruding). Try running that file and see if you get the error.
6. If you do get the error in 5 above and have a spare thrmocouple try attaching the spare thermocouple and run the test again.
7. If you do not get the error in 5 try adding Z moves into the test file.

I'm pretty busy at the moment and do not have max3155 hardware to test with so this may take some time to work through. You might want to join the discord server (see the wiki) and ask over there is anyone else is using max3155 and if they are seeing problems.

[gloomyandy]

One other question. Have you tried running the same print with a standard temperature sensor? It would be useful to know if you get any errors/disconnects in this case. It is possible that you have more than one problem here (the temperature reading and the disconnect).

[overdrive2max]

config.g

; https://duet3d.dozuki.com/Wiki/Gcode

; General preferences G90 ; send absolute coordinates... M83 ; ...but relative extruder moves M550 P"Zippy" ; set printer name

M667 S1 ; select CoreXY mode

; Drives M569 P0 S1 T0.1:0.1:0.02:0.02 D2 ; physical drive 0 goes forwards using default driver timings M569 P1 S1 T0.1:0.1:0.02:0.02 D2 ; physical drive 1 goes forwards using default driver timings M569 P2 S0 T0.1:0.1:0.02:0.02 D2 ; physical drive 2 goes forwards using default driver timings M569 P3 S0 T0.1:0.1:0.02:0.02 D2 ; physical drive 3 goes forwards using default driver timings

M584 X0 Y1 Z2 E3 ; set drive mapping

M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation M92 X80 Y80 Z160.45 E430 ; set steps per mm M566 X900.00 Y900.00 Z60.00 E2000.00 P1 ; set maximum instantaneous speed changes (mm/min) M203 X30000.00 Y30000.00 Z1000.00 E3000.00 ; set maximum speeds (mm/min) M201 X5000.00 Y5000.00 Z120.00 E1000.00 ; set accelerations (mm/s^2) M204 P1000.00 T5000.00 M906 X1000 Y1000 Z1200 E900 I70 ; set motor currents (mA) and motor idle factor in per cent ;M84 S20 ; Set idle timeout M593 F40.5 ;M593: Configure Dynamic Acceleration Adjustment

; Axis Limits M208 X0 Y0 Z0 S1 ; Set axis max travel M208 X298 Y300 Z300 S0 ; set axis maxima

; Endstops M574 X1 S1 P"xstop" ; configure active-high endstop for low end on X via pin xstop M574 Y1 S1 P"ystop" ; configure active-high endstop for low end on Y via pin ystop M574 Z1 S2 ; configure Z-probe endstop for low end on Z

; Z-Probe M558 P5 C"zstop" H2 F480 T9000 R1 A10 S0.03 ; set Z probe type to switch and the dive height + speeds G31 P300 X-31.7 Y0 Z10.2 ; set Z probe trigger value, offset and trigger height M557 X40:250 Y40:250 P5 ; define mesh grid

; Heaters M308 S0 P"bedtemp" Y"thermistor" T100000 B3950 ; configure sensor 0 as thermistor on pin bedtemp M950 H0 C"bed" T0 ; create bed heater output on bed and map it to sensor 0 M307 H0 B0 S1.00 ; disable bang-bang mode for the bed heater and set PWM limit M140 H0 ; map heated bed to heater 0 M143 H0 S130 ; set temperature limit for heater 0 to 130C ;M308 S1 P"th1" Y"thermistor" T98014 B4388 ; configure sensor 1 as thermistor on pin e0temp M308 S1 P"P1.21" Y"thermocouple-max31855" ; create sensor number 1 as a thermocouple, defaulting to type K in the first position on the Duet 2 ;daughter board connector M950 H1 C"he0" T1 ; create nozzle heater output on e0heat and map it to sensor 1 M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit

; Fans M950 F0 C"fan0" Q500 ; create fan 0 on pin fan0 and set its frequency M106 P0 S0 H-1 ; set fan 0 value. Thermostatic control is turned off M950 F1 C"e1heat" Q500 ; create fan 1 on pin he1 and set its frequency M106 P1 H1 T50 ; set fan 1 value. Thermostatic control is turned on at 50 deg C

; Tools M563 P0 D0 H1 F0 ; define tool 0 G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C

; Custom settings are not defined T0 ;select tool M501

I made a daughter board to connect the Pi and Max31855 to the ext connectors of the SKR. I added buck converters to supply 12v and 5v from the 24v supply and a linear regulator to supply 3.3v stable. Ground plane capacitance and loop has been mitigated in the design.

m122

m122 === Diagnostics === RepRapFirmware for LPC176x based Boards (biquskr_1.3) version 3.1.1-14 running on LPC176x at 100Mhz Used output buffers: 1 of 16 (12 max) === RTOS === Static ram: 4468 Dynamic Memory (RTOS Heap 5): 1688 free, 1664 never used Exception stack ram used: 448 Never used ram: 236 Tasks: HEAT(blocked,900) MAIN(running,1792) IDLE(ready,84) Owned mutexes: === Platform === Last reset 13:26:28 ago, cause: [software] LPC Flash Slot[31]: Last software reset at 2020-09-11 00:14, reason: User, spinning module LinuxInterface, available RAM 228 bytes (slot 0) Software reset code 0x0010 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0042a000 BFAR 0xe000ed38 SP 0x50004120 Task MAIN Stack: 00000004 100010d0 2007e1e0 00000001 000462c7 00000004 10000d40 2007e1e0 2007d1dc 00000004 Stack: 00040205 80000000 00000000 00000000 2009c020 00000001 00040caf 00040d80 41000000 10003f68 Stack: 00000000 00000000 10003048 Error status: 0 Driver 0: standstill, SG min/max 2/2, error r/w 0/0, ifcnt 100, cnt r/w 1774/0, timeout 0, failedOp 0xff Driver 1: standstill, SG min/max 2/2, error r/w 0/0, ifcnt 100, cnt r/w 1774/0, timeout 0, failedOp 0xff Driver 2: standstill, SG min/max 0/0, error r/w 0/0, ifcnt 130, cnt r/w 1773/0, timeout 0, failedOp 0xff Driver 3: standstill, SG min/max N/A, error r/w 0/0, ifcnt 73, cnt r/w 1774/0, timeout 0, failedOp 0xff Date/time: 2020-09-11 13:41:19 Slowest loop: 4.80ms; fastest: 0.38ms Watchdog timer: 6243601/6250000 Step timer: target 1115866291 count 1144301269 delta -28434979 late 0 USBSerial connected 0 ADC not ready 0 ADC error threshold 10 ADC Init 1 Ints: 15891; Calls 37079; fast: 4uS; slow 22uS adj 63 bad 0 big delta 0 PWM Channels state 0 next 21159 on 32150(1) off 67850(0) pin 2.7 state 1 next 21159 on 50000(0) off 50000(0) pin 2.3 state 2 next 21159 on 50000(1) off 50000(1) pin 2.4 state 3 next 21159 on 100000(0) off 100000(0) pin 2.5 Delta 21159 Start 0 End 4 === Move === Hiccups: 0, FreeDm: 100, MinFreeDm: 100, MaxWait: 0ms Bed compensation in use: mesh, comp offset -0.006 === DDARing === Scheduled moves: 101506, completed moves: 101506, StepErrors: 0, LaErrors: 0, Underruns: 0, 0 CDDA state: -1 === Heat === Bed heaters = 0, chamberHeaters = -1 Heater 0 is on, I-accum = 0.1 Heater 1 is on, I-accum = 0.4 === GCodes === Segments left: 0 Movement lock held by null HTTP is ready with "M122" in state(s) 0 Telnet is idle in state(s) 0 File is idle in state(s) 0 USB is idle in state(s) 0 Aux is idle in state(s) 0 Trigger is idle in state(s) 0 Queue is idle in state(s) 0 LCD is idle in state(s) 0 SBC is idle in state(s) 0 Daemon is idle in state(s) 0 Aux2 is idle in state(s) 0 Autopause is idle in state(s) 0 Code queue is empty. === Linux interface === State: 0, failed transfers: 0 Last transfer: 11ms ago RX/TX seq numbers: 49232/49234 SPI underruns 0, overruns 0 Number of disconnects: 0 Buffer RX/TX: 0/0-0 === Duet Control Server === Duet Control Server v3.1.1 Code buffer space: 2048 Configured SPI speed: 8000000 Hz Full transfers per second: 32.79

My cable run to the hotend runs past my X motor and the E motor (Not ideal I know). When X, Y and Z is moving there is no issue.

The disconnect becomes more frequent when the E stepper motor is engaged (moving or idle). When I print, most of the time it does not fail. The temperature spike (disconnect condition) lasts for 1 cycle on the graph by the looks of it. Sometimes it is longer and the print will fail due to heater failure condition.

Using a 100k thermistor has no issue at all, everything works.

What bugs me is that it should not be interference causing my issue as the K-type readings is voltage based. Thus, emi would cause erratic temperatures, not a disconnected probe reading of 2000C.

It feels like the software SPI is not functioning or reporting fast enough.

Kind regards

[sdavi]

Yes, most likely it's cause your using Software SPI for the max31865 connection. It may not like the variations in the software generated signals caused by the extra interrupts that are used for stepper movement when printing. Most users use the max31865 connected SSP0 on the LPC port (myself included), but since you also have the SBC connected, the only other choice is SSP1 (if your board has headers for those pins).

[overdrive2max]

That was my suspicion. Can the ss SPI rate not be lowered to achieve stability?

[overdrive2max]

I have to apologise for not doing proper research on this issue. It seems it was brought up on the RRF forums and a fix was proposed. I can confirm it has solved my issue on initial testing. By adding a bypass cap of 10nf per thermocouple terminal to ground solved my issue.

https://forum.duet3d.com/topic/1270/thermocouple-issues/11

[gloomyandy]

@overdrive2max Thanks for the update. Please let us know if it still seems to be working after further testing.