DK, I also want to use the Clearpath Teknic motors driven from a Duet. Have you been able to get this working? I spoke to Teknic support and they confirmed the need for 5V .8mA minimum signal.
There is another thread discussing using a Duex board with external drivers so you can have additional I/O.
"Unfortunately that isn't going to work, because when a DueX5 is connected, the firmware knows that the stepper motors on the expansion bus use TMC2660 drivers, and it drives them accordingly. Even with a firmware change, the unused driver chips would interfere with the status reports from the other TMC driver chips.
Here are some other options:
•the latest beta firmware supports 2 additional drivers connected to the CONN_LCD connector
•if you use a DuetX2 instead of a DueX5 then you can connect 3 external stepper drivers to the expansion bus
•it's possible to remove the last 3 stepper driver chips from a DueX5 and change a few resistors to make it identify itself as a DueX2 so that you can again use 3 external drivers. The additional heaters, fans etc. will still work even though a DueX2 doesn't have them.
Btw the voltage output by the external driver interface board is somewhat less than 5V in practice. It should be possible to get close to 5V out by wiring the + inputs of your drivers directly to +5V instead of to the + output pins provided on the board."
I am concerned that the external driver signal is a little less than 5V. The ClearPath has 5V .8milliamp as a minimum.
Is there another way to boost the .2mA 3.3V signals?