In Marlin firmware, I could get the current position of an extruder with this function:
y = float(st_get_position(Y_AXIS)/axis_steps_per_unit[Y_AXIS]) ;
Is there the same thing in Duet firmware? I would like it to get the current position even if it is in the middle of a straight move. For example, If it is as X0, and it is traveling to X100, then when it triggers a sensor, I would like to know the current position of each time it is triggered during that move.
@T3P3Tony No worries, I figured! But I will keep my fingers crossed 
@dc42 Based on your message, it sounds like it could make it into the next build? If so, thanks!
@dc42 I would think 4 would be enough to cover most things. 5 or 6 would be enough for future flexibility. Maybe 256 just to be safe 
just kidding.
@dc42 Thanks for the quick replies both of you!
I think M42 is not suitable since I would like to send more than a just a Yes/No or PWM signal. The "User Defined" sounds like its exactly what I'm looking for! I hope its not too difficult to implement.
@T3P3Tony Is there a list of canfd messages I can see? I don't want to have to modify the firmware to send messages, so if I can do it with existing messages, that would be great.
My theoretical external PCB/system on a custom extruder may take various CAN commands to do various things like: activatePump4, setPumpSpeed4, setPump4Duration, stopPump4, activateDAC1, setDAC1voltage, runDAC3VoltageSequence2, startCamera2, setCam2ExposureTime, runMachineVisionAlgorithm7, runValveActivationSequence5, setHumidity, etc
Its useful for things that have already been set up externally outside of the Duet system, working fine, but now I just want the Duet to launch many of those things by just sending a message through CAN.
For Example:
M265 P3:2:444:5:1 ; runs 3rd custom command with parameters 444, 5, and 1
(the 3rd command could be "runPump", the 2 could mean the 2nd pump, 444 means the speed, 5 is duration, etc)
Or as a more extreme example, maybe I have a multi-channel DAC that needs to output a sinusoidal wave from its 2nd output at 10 Hz for 4 seconds with a 5V amplitude, then at 4 Hz for 1 second at 2V amplitude. And the needs might change from print to print because I am experimenting. It would be nice to be able to just write these two lines to do it:
M265 P8:2:10:4:5 ; activate DAC, channel 2, 10Hz, 4 sec duration, 5V amplitude
M265 P8:2:4:1:2 ; activate DAC, channel 2, 4 Hz, 1 sec duration, 2V amplitude
Let me know if you have any ideas on how to do this without existing CAN messages. If not, it would be great to have an M265. I imagine this would be very useful for research labs developing new kinds of 3D printers or doing 3D printing related research.
@jml nevermind - I had to sign in in order for github to show Code results. Thanks!
(is there a way to mark this post solved?)
@Falcounet Thank you for finding it! Can you teach me how to do the search? When I do it, github cannot find SendMessage or CanDevice.h.
This is what I search:
org:Duet3D SendMessage
org:Duet3D CanDevice.h
Similar to how M260 exists for sending data over I2C, it would be great to have a similar command for CAN-FD.
That would allow me to create a separate PCB to take care of some other things independently. Like an exotic extruder with some kind of custom functionality.
CanDevice.h I still cannot find. But I found this:
https://github.com/Duet3D/CANlib
which includes the CanId and the CanMessageFormats, but still can't find CanDevice.h 
I was just trying to understand how the CAN messages work. In CanInterface.cpp, I can see these functions (each calling on the next):
SendRequestAndGetStandardReply
SendRequestAndGetCustomReply
SendCanMessage
SendMessage
However, SendMessage is not defined anywhere. I think it should be within CanDevice.h, but CanDevice.h isn't anywhere, nor is CanId.h, or CanMessageFormats.h - yet these are #included in some of the .cpp files.
Is the repository missing these? Or are we supposed to get these header files elsewhere?
What is the default heater pwm frequency for extruders? And is it possible to change it? I have heard that for Peltier chips, we should use a fast frequency PWM and I heard that typical heater PID PWM is too slow. Thank you.
I tried a different Duet board and put the same 4 folders (and firmware) onto the SD. M997S0 worked fine (whereas the same 4 folders on the previous Duet didn't work).
On closer inspection I saw that the fan fuse was actually broken. I had replaced that fuse a while ago and the new one must have been damaged when inserting it in with pliers. I don't think that is the issue though because I then shorted the fuse manually with a metal piece and M997 still didn't work.
I don't have the time to troubleshoot the anti-M997 Duet board much, but I'm going to classify it as a hardware/electrical issue that probably happened when there was a fan-related short.
@T3P3Tony for the 2.5.1 wifi server, do you mean DuetWifiServer1.23.bin? That is the one I see here:
https://github.com/Duet3D/RepRapFirmware/releases/tag/2.05.1
I'm using the DuetEthernet by the way, and don't have my internet working currently, so maybe it doesn't matter.
Thanks Tony I'll try that. Will let you know in a day or two, thanks!
I just tried via USB and mac terminal. Same response. M115 works fine. M997S0 just resets the board and the screen has no message or reaction.
Thank you for the suggestion. I downloaded the new Iap4 file, it did not help unfortunately.
I tried replacing the sys folder with a backed up sys file from November which I know had worked back then, but it also has the same result - M997 S0 just restarts the printer instead of installing new firmware.
The SD appears to work fine - I can launch a print or macro from the screen no issues there.
I have internet problems but can try uploading via DWC when it gets fixed. Is that worth a try, or do you think it might be something else? Should I try doing M997 S0 through USB connection? I have been doing it through the screen.
I’m on 2.01 because I had edited the firmware slightly back in those days and didn’t ever upgrade to anything newer. What I’m trying to upload is a modified 2.01 (simple custom gcode modification). I have been doing this for weeks on this Duet but it suddenly stopped working. I’ll try the download what was suggested above, thank you.
The SD card appears to be working correctly. Macros and gcodes are viewable from the screen.
From the screen, M21 outputs "SDHC card mounted in slot 0, capacity 7.95GB" and M39 outputs "SD card in slot 0: capacity 7.95GB free space 7.71Gb, speed 20.00MBytes/sec, cluster size 64kb"
I used to use "M997 S0" from the screen to make the Duet load the new Duet2CombinedFirmware.bin file. Normally the screen would output dialog saying that its installing new firmware.
But instead, it seems like the Duet just power cycles. The behavior appears identical to pressing the STOP button.
Has this happened to anyone before? How did you fix it?
Note I'm using Firmware version 2.01 on DuetEthernet. M997 S0 had been working fine for many months.
Anyway, I've tried the new 2019 q4 major update, and it is not improving the results at all. Still lots of the same error like undefined reference to `pow'. Hmmmm