In the first version of the TMC board i tried INA282 current shunt amplifiers.

It turns out despite having very good specs on paper they are extremely susceptible to fast rising common mode voltages.

And we have these a lot as the TMC needs to measure currents on the floating motor outputs.

This meant extremely bad noise on the current measurements.
As an alternative there are the AD8417 which are much better suited for this application for the same price.

See for yourself what a difference this makes:

Looks pretty good considering that this is on a low scale and we can go MUCH higher and maybe even improve the noise with filter tuning.

Looks very bad right?
This is because the INAs output spikes >1V up or down for up to 15µs after almost every pwm cycle (25-50khz).

This is the output of the INA282 with no motor current. Only pwm active. yup. pretty bad.

Obviously we are now using the AD8467. For even better noise the AD8468 with low gain could be used but this would decrease the maximum current even more. I am aiming for >25A fullrange for this version for now.

By using different shunts or the lower gain AD8468 we can decrease or increase the limit depending on the application.

We will also add low pass filters to the encoder and hall inputs as with some motors significant pwm noise gets back through these lines and causes glitches. This means even more components to solder :/

Next step is to order new pcbs to fix the previous errors and write the firmware.
The firmware is currently in a stage where most base features are working and i am implementing an example for FFB soon

Also as the board is quite small there is not much room to add capacitors causing high ripple on the motor voltage rail when backdriven as there is currently only space for one larger cap.
When used with large motors it is recommended to add external caps between GND and PB+.