TMC2209 max speed

Hi all, I am designing/building a custom pick-and-place machine with off-the-shelf dual nozzle head to be controlled with OpenPnP. The mechanical part is working nicely and I am currently evaluating controller options.

I tried Synthethos g2core first, because it has 6-axis support and I previously designed a shield for it for onboard A4988/DRV8825/TMC2209 drivers. With g2core, these drivers are all working smoothly, max speeds of 2 m/s (unloaded) and 1 m/s (loaded) were achievable.

Because OpenPnP supports Smoothieware well, I built and installed the 5-axis CNC version on a cheap MKS SGEN_L v2 board (It has all the outputs my machine needs on a single small board. Unfortunatley I just found out Makerbase does not apply open-source principles very well). Now with only unconnected NEMA17 motors the TMC2209 drivers can’t go much faster than 0.2 m/s, but with the A4988/DRV8825 drivers it still works smoothly at higher speeds. Drivers/motors/microstepping/etc are the same. Motor voltage between 12-24V makes no difference. Who has got a clue? Is the pulse width maybe too small for the TMC2209? Is there someone with experience with TMC2209, Smoothieware and/or MKS boards?

Support to running the TMC drivers in UART mode lives only on a branch, and might be key to going faster (I don’t actually know; it’s just conjecture).

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Thanks, UART is nice for configuring things like microstepping and max current. Higher speed should be possible using the dir/step/enable input as these same drivers work correctly on g2core (without UART support)