checklist for custom expansion board
-
What would be needed to run a custom expansion board with duet 3 mainboards?
Is it enough to have the custom firmware and bootloader on the sd card or does it require a modified firmware for the mainboard too?
How many gpio ports are currently allowed on a custom expansion board?
-
@petm said in checklist for custom expansion board:
What would be needed to run a custom expansion board with duet 3 mainboards?
You need a board that supports CAN-FD. Easiest if you are starting from the master firmware for expansion boards (Duet3Expansion) is to base it on a Microchip processor that supports CAN-FD. If you want it to support motion with input shaping then choose a SAME5x processor (SAME70 would also be possible but we don't provide a CAN-FD bootloader for it). If it's for heaters, fans, gpio and other less time-critical devices then the SAMC21 is likely to be sufficient. The SAMMYC21 board may be useful for prototyping such a device.
Is it enough to have the custom firmware and bootloader on the sd card or does it require a modified firmware for the mainboard too?
The bootloader generally needs to be programmed into the expansion board. The firmware can be on the SD card of the main board because our bootloader will request firmware from the man board over CAN-FD.
How many gpio ports are currently allowed on a custom expansion board?
The only limit is the total number of gpio ports in the whole Duet3 system, which is 64.
-
Thank you very much for the fast response. Yes, the Atmel SAMC are ideal candidates for simple CAN-FD solutions.
What possibilities are there to circumvent this 64 GPIO limit?
For example, if you wanted to address 100 ports (simple outputs without PWM) individually on an expansion board, would there be any way to do this, e.g. via M42 or perhaps with another existing gcode?
-
@petm you could circumvent this limit by configuring up to 64 gpout ports and up to 56 fan ports. You would control the gpout ports using M42 and the fan ports using M106.
Another possibility with RRF 3.6 on Duet 3 boards would be to use Modbus devices to provide some of the output ports and turn them on/off using M260.1 calls.
-
@dc42, the Modbus sounds very interesting, but I think CAN-FD is the more fail-safe system.
Creating a bootloader and firmware for a SAMC21N18A went smoothly and because of the GPIO limit I also found a way to address many more ports.
As a newbie, i'm still impressed by the many possibilities that duet3d has to offer.
