Hi,
- Custom Carrier
- IMX8M+ (V1.1B)
- MAX3232 – RS232 to USB adapter
We are developing a custom carrier board based of the Verdin development board. We have a halfway design to our final form factor that still has a lot of the circuitry of the verdin development board.
We are seeing that while programming through recovery and the USB debug port we get “Failure to open USB device”. However, if we attempt to program with a MAX3232 serial to USB converter connected to UART 3 RXD and TXD it is successful.
The USB Debug circuitry is carried over from the Verdin development board and UART3 has been stripped right back to only a breakout connector connected to the RS232 adapter.
Have you seen anything similar before?
Many thanks,
George
Hello @G_Third,
Welcome to the Toradex Community!
I am pretty sure that the issue you have is noise on the UART_3 RX line.
Can you try to connect only the UART_3 TX line and see the serial output from the SoM?
If there is noise, I would expect that the process will still fail and you will be able to see garbage in the serial terminal.
Best Regards,
Bruno
Hi @bruno.tx,
Thanks for your quick reply. After a bit of experimentation.
Both TX and Rx connected (with or without MAX3232 connected to PC)
Boot is successful.
U-Boot 2022.04-6.8.0+git.a1eb18d157.txt (7.1 KB)
With TX only connected:
It fails
Failed U-Boot SPL 2022.04-6.8.0+git.a1eb18.txt (1.4 KB)
With RX only connected:
Works as RX+TX but with no data fed back (obviously)
Thanks,
George
Hello @G_Third,
Thanks for the update.
The failed logs do show that u-boot was interrupted due to noise, but the output was cleaner than expected.
Regardless, the issue still seems to be noise on the Rx line.
This can be caused by interference from other circuitry on the board.
Avoiding such interference would be recommended.
Otherwise, using a pull-up resistor on the Rx Line would reduce the likelihood of the noise being read by the board.
Best Regards,
Bruno
