Is ypspur-coordinator not supported in ubuntu 22.04?

[yamazak]

I tried to use TF-2MD3-R6 motor driver with the latest ypspur and firmware. Both software is compiled on Ubuntu 22.04 and I run ypspur-coordinator with this ubuntu.
Sometimes the connection with the motor driver was rejected, or even if I could, a high-pitched sound may be heard. Additionally, when a load is applied to the motor, the ypspur-coordinator process terminates. Since I have three motor drivers, I tried the same thing for all of them, but the result was the same.

I also tried the same procedure using ubuntu20.04, then it works (I was able to run run-test.c).

[at-wat]

I don't usually use Ubuntu, but yp-spur should support Linux environments newer then Ubuntu 20.04.

Please make sure that ttyACM* of TF-2MD3-R6 is not used by other processes like ModemManager which opens all ttyACM devices by default.
ref: https://stackoverflow.com/questions/24696527/modem-manager-and-ttyacm-in-use

[BND-tc]

@yamazak I experienced the same issue. As a quick workaround, I was able to get it working by downgrading the kernel to version 5.15.

[BND-tc]

As a temporary workaround, I was able to get YP-Spur working on a 6.8 kernel by applying the following change:

```diff
diff --git a/src/serial.c b/src/serial.c
index 6aa5751..8dd7c77 100644
--- a/src/serial.c
+++ b/src/serial.c
@@ -533,7 +533,7 @@ int encode_write(char* data, int len)
   {
     return -1;
   }
-  serial_flush_out();
+  //serial_flush_out();

  return 0;
}

The issue occurred after executing init_command_thread(), specifically in odometry_receive_loop(). This loop communicates with the motor driver every 5ms to receive encoder and PWM values.

Although select() waits correctly for incoming data, but read() returned 0. In another thread, motor velocity commands were sent using write(), followed by tcflush(g_device_port, TCOFLUSH); to flush the output buffer.

Normally, flushing the output buffer should not affect the input buffer. However, on the 6.8 kernel, it seems that both input and output buffers were being flushed simultaneously. Disabling the flush resolved the issue, but further investigation is needed to confirm the behavior.

[yamazak]

Thank you for your great effort & sorry for my late response. I was finally able to test it and confirmed that the modification to serial.c works correctly. The same modification was also effective on Ubuntu 24.04!