UART connection issues

[haub94]

First: thanks for this great lib! :)

Setup: Raspberry Pi 3 B with Raspbian:latest + TMC2209@Bigtreetech V1.3 + NEMA8 / every connected like in the README explained

I'm tried the last days to run the stepper trough UART but the most time i got the error/log (debug_script_01_uart_connection.py), that the data which were sent and the received one are not the same. Sometimes the program freeze and after killing it, i got the log:

/app/repo/TMC2209_Raspberry_Pi/demo # python3 debug_script_01_uart_connection.py 
---
SCRIPT START
---
2025-01-22 15:26:34,811 - TMC2209 0 - INFO - Init
2025-01-22 15:26:34,812 - TMC2209 0 - INFO - GPIO Init finished
2025-01-22 15:26:34,812 - TMC2209 0 - INFO - Init finished
---
---
2025-01-22 15:26:34,813 - TMC2209 0 - INFO - ---
2025-01-22 15:26:34,814 - TMC2209 0 - INFO - TEST UART
^CTraceback (most recent call last):
  File "/app/repo/TMC2209_Raspberry_Pi/demo/debug_script_01_uart_connection.py", line 62, in <module>
    tmc.test_uart()
  File "/usr/local/lib/python3.9/site-packages/TMC_2209/_TMC_2209_test.py", line 92, in test_uart
    result = self.tmc_uart.test_uart(tmc_reg.IOIN)
  File "/usr/local/lib/python3.9/site-packages/TMC_2209/_TMC_2209_uart.py", line 333, in test_uart
    rtn = self.ser.write(self.r_frame)
  File "/usr/local/lib/python3.9/site-packages/serial/serialposix.py", line 640, in write
    abort, ready, _ = select.select([self.pipe_abort_write_r], [self.fd], [], None)
KeyboardInterrupt
2025-01-22 15:27:43,089 - TMC2209 0 - INFO - Deinit
2025-01-22 15:27:43,090 - TMC2209 0 - INFO - Motor output active: False
2025-01-22 15:27:43,091 - TMC2209 0 - INFO - GPIO cleanup
2025-01-22 15:27:43,093 - TMC2209 0 - INFO - Deinit finished

Rarly the debug_script_01_uart_connection.py runs well and i got the log:

---
SCRIPT START
---
2025-01-22 14:43:00,377 - TMC2209 0 - INFO - Init
2025-01-22 14:43:00,378 - TMC2209 0 - INFO - GPIO Init finished
2025-01-22 14:43:00,379 - TMC2209 0 - INFO - Init finished
---
---
2025-01-22 14:43:00,379 - TMC2209 0 - INFO - ---
2025-01-22 14:43:00,380 - TMC2209 0 - INFO - TEST UART
2025-01-22 14:43:00,385 - TMC2209 0 - DEBUG - received 12 bytes; 96 bits
2025-01-22 14:43:00,386 - TMC2209 0 - DEBUG - hex: 550006e805ff06210002419d
2025-01-22 14:43:00,386 - TMC2209 0 - DEBUG - bin: 010101010000000000000110111010000000010111111111000001100010000100000000000000100100000110011101
2025-01-22 14:43:00,391 - TMC2209 0 - DEBUG - length snd: 4
2025-01-22 14:43:00,392 - TMC2209 0 - DEBUG - length rtn: 12
2025-01-22 14:43:00,392 - TMC2209 0 - DEBUG - complete messages:
2025-01-22 14:43:00,392 - TMC2209 0 - DEBUG - 550006e8
2025-01-22 14:43:00,392 - TMC2209 0 - DEBUG - 550006e805ff06210002419d
2025-01-22 14:43:00,393 - TMC2209 0 - DEBUG - just the first 4 bits:
2025-01-22 14:43:00,393 - TMC2209 0 - DEBUG - 550006e8
2025-01-22 14:43:00,393 - TMC2209 0 - DEBUG - 550006e8
2025-01-22 14:43:00,394 - TMC2209 0 - DEBUG - the Raspberry Pi received the sent
                            bits and the answer from the TMC
2025-01-22 14:43:00,395 - TMC2209 0 - DEBUG - the Raspberry Pi received exactly the bits it has send.
                    the first 4 bits are the same
2025-01-22 14:43:00,396 - TMC2209 0 - INFO - ---
2025-01-22 14:43:00,397 - TMC2209 0 - INFO - UART connection: OK
2025-01-22 14:43:00,398 - TMC2209 0 - INFO - ---
---
---
2025-01-22 14:43:00,399 - TMC2209 0 - INFO - Deinit
2025-01-22 14:43:00,399 - TMC2209 0 - INFO - Motor output active: False
2025-01-22 14:43:00,400 - TMC2209 0 - INFO - GPIO cleanup
2025-01-22 14:43:00,401 - TMC2209 0 - INFO - Deinit finished
---
SCRIPT FINISHED
---

Controlling the stepper with STEP/DIR works well.

Have you ever had such an situation and/or can you explain me what I'm doing wrong?

[Chr157i4n]

Hey,

can you please also post a log, where the recceived data was not correct.

When having UART problems please check the following to rule out wiring issues:

• GND connection between Pi and TMC2209
• Connection between PDN_UART of the TMC2209 and TX/RX of the Pi
• 1kOhm resistor between TX and RX of the Pi

And no, i did not have such an issue (i am using a RPi4).
Your first log indicates that the freeze appears to be happening in the pyserial library.
Maybe related to this:
pyserial/pyserial#163

That issue seems to be happening when there is no write_timeout. Try setting not just the timeout, but also the write_timeout here:

TMC2209_Raspberry_Pi/src/TMC_2209/_TMC_2209_uart.py

Line 75 in 9e39949

self.ser.timeout = 20000/baudrate

This could prevent the Pi from hanging if no response is received. However, this does not solve the original problem.

[haub94]

Thank you for the fast response!
I checked all your suggestions - everything is fine connected.

Here is the "UART not ok" log:

/app/repo/TMC2209_Raspberry_Pi/demo # python debug_script_01_uart_connection.py 
---
SCRIPT START
---
2025-01-22 16:01:01,031 - TMC2209 0 - INFO - Init
2025-01-22 16:01:01,032 - TMC2209 0 - INFO - GPIO Init finished
2025-01-22 16:01:01,033 - TMC2209 0 - INFO - Init finished
---
---
2025-01-22 16:01:01,035 - TMC2209 0 - INFO - ---
2025-01-22 16:01:01,036 - TMC2209 0 - INFO - TEST UART
2025-01-22 16:01:07,811 - TMC2209 0 - DEBUG - received 12 bytes; 96 bits
2025-01-22 16:01:07,812 - TMC2209 0 - DEBUG - hex: 5b4b5b2020201b69742e7365
2025-01-22 16:01:07,812 - TMC2209 0 - DEBUG - bin: 010110110100101101011011001000000010000000100000000110110110100101110100001011100111001101100101
2025-01-22 16:01:07,817 - TMC2209 0 - DEBUG - length snd: 4
2025-01-22 16:01:07,818 - TMC2209 0 - DEBUG - length rtn: 12
2025-01-22 16:01:07,818 - TMC2209 0 - DEBUG - complete messages:
2025-01-22 16:01:07,818 - TMC2209 0 - DEBUG - 550006e8
2025-01-22 16:01:07,819 - TMC2209 0 - DEBUG - 5b4b5b2020201b69742e7365
2025-01-22 16:01:07,819 - TMC2209 0 - DEBUG - just the first 4 bits:
2025-01-22 16:01:07,819 - TMC2209 0 - DEBUG - 550006e8
2025-01-22 16:01:07,819 - TMC2209 0 - DEBUG - 5b4b5b20
2025-01-22 16:01:07,820 - TMC2209 0 - DEBUG - the Raspberry Pi received the sent
                            bits and the answer from the TMC
2025-01-22 16:01:07,820 - TMC2209 0 - DEBUG - the Raspberry Pi did not received the bits it has send.
                    the first 4 bits are different
2025-01-22 16:01:07,820 - TMC2209 0 - INFO - ---
2025-01-22 16:01:07,821 - TMC2209 0 - ERROR - UART connection: not OK
2025-01-22 16:01:07,821 - TMC2209 0 - INFO - ---
---
---
2025-01-22 16:01:07,821 - TMC2209 0 - INFO - Deinit
2025-01-22 16:01:07,821 - TMC2209 0 - INFO - Motor output active: False
2025-01-22 16:01:07,822 - TMC2209 0 - INFO - GPIO cleanup
2025-01-22 16:01:07,823 - TMC2209 0 - INFO - Deinit finished
---
SCRIPT FINISHED
---

Next i will test it with an RPi4 and share the results with you.

[Chr157i4n]

So for me this looks like the TMC2209 does receive the message sent from the Pi and answers but the Pi does only receive garbage on the RX pin. Even the bytes the Pi sent on the TX pin are not received correctly by the Pi itself.
Maybe try a lower baud rate.

[haub94]

Finally i got it.
I played around with the baudrate but it doesn't solved my prolem. So i installed a fresh Raspberry OS and it works instant.
Thanks for your fast support :)