i am trying to activate the UART on the tronxy drivers
I connected the DM uart on some free pads which would have been needed for an optional E1 driver
from other info I have seen that this mod works on Klipper, so I take for granted the presence of a resistance between tx and rx ... I have not checked.

activated tmc_debug, and changed the description of the drivers from TMC2208_ STANDALONE to TMC2208,
now M122 works, but I am error TESTING CONNECTION ... ERROR: ALL LOW, sometimes on one driver, other times on all.


do you have any ideas or proofs to suggest? other marlin settings to try ....

I know this is very old, but since I was probably not the only one to stumble over this, here's how it seems to work fine for me in Marlin.
You basically just need to add a 20k resistor between each pin and GND (I didn't have a 20k on hand, so I used 22k, but even 10k is likely fine).

Just wanted to follow up on this:

I've modded my Tronxy X5SA according to the specs and it works in klipper even without a resistor.
The E1 stepper is turned around on the board and in the drawing the E2 stepper is shown mirrored, but appart from that it works. the pin numbers in the drawing for E2 are correct.

Do you have your klipper printer,cfg for this uart mod
:-)