TMC2208 in UART mode on the SKR v1.3

I'm trying to get the SKR v.13 controller up and running with the TMC2208 stepper drivers. There are plenty of tutorials online on how to do this so it looks pretty easy. However, I cannot get communication with the driver to work. I am attaching my configuration files and the pins file I'm using.

I have removed the 4 jumpers under the driver and I have inserted a jumper on the XUART position to connect the UART to the LPC1768 GPIOs. The TMC2208 stepper driver I'm using is the v3 version from BigtreeTech. It has the J2 pads bridged so that PDN_UART is connected as needed. When I use the M122 command, I get:

Send: M122
Recv: 		X	Y
Recv: Enabled		false	false
Recv: Set current	600	800
Recv: RMS current	1049	1436
Recv: MAX current	1479	2025
Recv: Run current	18/31	25/31
Recv: Hold current	9/31	12/31
Recv: CS actual		0/31	0/31
Recv: PWM scale	0	0
Recv: vsense		0=.325	0=.325
Recv: stealthChop	false	false
Recv: msteps		256	256
Recv: tstep		0	0
Recv: pwm
Recv: threshold
Recv: [mm/s]
Recv: OT prewarn	false	false
Recv: OT prewarn has
Recv: been triggered	false	false
Recv: off time		0	0
Recv: blank time	16	16
Recv: hysteresis
Recv: -end		-3	-3
Recv: -start		1	1
Recv: Stallguard thrs
Recv: DRVSTATUS	X	Y
Recv: stst
Recv: olb
Recv: ola
Recv: s2gb
Recv: s2ga
Recv: otpw
Recv: ot
Recv: 157C
Recv: 150C
Recv: 143C
Recv: 120C
Recv: s2vsa
Recv: s2vsb
Recv: Driver registers:
Recv: 		X	0x00:00:00:00	 Bad response!
Recv: 		Y	0x00:00:00:00	 Bad response!
Recv: 
Recv: 
Recv: Testing X connection... Error: All LOW
Recv: Testing Y connection... Error: All LOW
Recv: ok

If I probe the UART pin on the stepper driver with an oscilloscope, I see what looks to be reads that never return data. Looking at the TMC2208 datasheet, I see the sync byte (0xA0) followed by a byte of zeroes, and a register value of 0x6F (0xF6 flipped MSB to LSB since the bits are transmitted LSB first) which is the DRV_STATUS register. The sequence is two reads about 11 mS apart and those are repeated every 500 mS.


Can anyone see what's wrong here?

I should also mention that I have configured the Y axis with the same configuration as the X axis. I see the same UART signals on both. This suggests to me that it's not just a bad TMC2208. Since the controller is sending requests and not getting an answer, this seems to point to a problem in the stepper driver configuration. From the documentation I have, there is not much to do, configuration-wise, other than putting a solder bridge on J2 which was already there from the factory.

miefevre I'm close to getting to this stage so was this solved or did you revert to two steppers on one driver. Is it A UART problem.