Are the source files of Duet 3 ToolBoard 1.2 available?

zapta

Thanks @t3p3tony! This is very useful.

My first goal is to strip the iLC I got from everything that is not needed for accelerator operation and then build a small board with only that functionality. My long term goal is to be able to build custom tool or sensor boards that are compatible with Duet 3. I believe that if this will work, it will enrich and support the Duet3/Reprap eco system.

Edit: this is the plan. It's yet to see how far I will get with it.

dc42

@zapta if you just want the accelerometer, then run the SAMC21 from +3.3V instead of +5V to avoid needing the level shifters between the accelerometer and the SAM. You should still run the CAN transceiver main supply from +5V (and the VccIO supply from +3.3V). This is how we use an accelerometer on the SAMMYC21. The main reason we run the SAM from +5V on the tool board is to get 5V drive to the OUT0 mosfet.

zapta

Thanks @dc42, this is a good idea. I plan to cut my own PCB with a subset of the schematic of the toolboard but your advice still applies.

I presume that the BOARD_TYPE divider (22K, 1K) will still work with 3.3V since the ADC is also scaled to 3.3V and that the ATSAMC21G18A can run on same frequency. This will make the schematic of the accelerometer only CAN bus node almost trivial.

zapta

@T3P3Tony, @dc42, I created the initial schematic, dropping all the things I think are not needed for an accelerometer only board. Do you mind taking a look at the schematic and let me know if it's reasonable?

https://github.com/zapta/duet_micro_tool/blob/main/kicad/duet_micro_tool.pdf

Also, a few more specific questions:

Is it OK to leave open all the unused inputs such as USART_RX or TACHO_ ?
Are the power monitoring voltage dividers and signals necessary (I dropped them)
Do you expect that I will be able to flash it with the stock Duet toolboard binary and have the accelerometer working?
I was not sure what to put in the LICENSE file on github. I don't have any claim on my contribution but it's is derived from your work. Any suggestion for third party contributors like me?

Thanks.

T3P3Tony

@zapta I will leave the other questions up to David, for the license please see the duet 3 License (which I will also add to the toolboard repository):

https://github.com/Duet3D/Duet3-Mainboard-6HC/blob/master/LICENSE

zapta

Thanks @t3p3tony , I will update the license accordingly. The only concern is this requirement:

... must contain the following attribution on the PCB silkscreen: "Based on the design by Duet3D, see www.duet3d.com for the original product. This reproduction/modification is not endorsed or supported in any way by Duet3D".

It assume a certain minimal size of boards. I hope to have a tiny board. Any suggestions?

T3P3Tony

@zapta if it can't fit on the board then it should be in on the packaging if its commercially packaged. Depends how you distribute the board. Once you have a plan then feel free toc heck in with info@duet3d.com to clarify any details.

zapta

Sounds good. Thanks @t3p3tony.

PCR

@T3P3Tony i once saw a toolboard from a Twitter user which were black. You said that something will be revealed. Any news about that?

Best

dc42

@zapta I don't have time to do an in-depth review of your schematic, however I spotted the following:

You should add pullup resistors between the two I2C data lines and +3.3V.
I suggest you include the ACT LED and perhaps the CAN LED from the original schematic, so that you can tell when the board has CAN sync, and so the bootloader can flash error messages.
The board type resistor values and some of the MCU pin allocations don't correspond with the tool board 1.2 schematic at https://github.com/Duet3D/Duet3-Toolboard-1LC/blob/master/ToolBoard_1LC_v1.2/Duet3_TB_1LC_Schematic_v1.2.pdf.
You may be able to use the ATSAMC21E18A instead of ATSAMC21G18A if it provides all the pins that you use (I haven't checked).

If you intend to run the standard tool board firmware on it then you should tie the unused input pins to +3.3V through resistors, because the standard firmware disables the internal pullup resistors. The standard firmware expects the VIN monitor divider to be present, so best add that voltage divider.

zapta

Thanks @dc42, this is very useful. The new schematic after the changes is here https://github.com/zapta/duet_micro_tool/blob/main/kicad/duet_micro_tool.pdf

I still have a couple of questions if it's ok.

Do I need to pull up also the LIS2DH INT1 output?
I was not sure what unused pins to pull up so prepared this list https://github.com/zapta/duet_micro_tool/blob/main/kicad/TODO.txt , is it correct? Also, can I tie together all or groups of inputs to reduce the number of pull up resistors used?

Also, have you considered setting the inputs to have internal pull up/down by default? This may make the firmware more versatile for custom tool boards.

(I am yet to look at ATSAMC21E18A, my current thinking is to stay as close as possible to the Duet toolboard).