Serial Port boots with garbage communication

[colinc]

Using the newer kernel, AM3352-SOM Debian image with kernel 4.4.xx release 5, with the uEnv.txt file edited to use the am335x-olimex-som-evb.dtb, the serial port return ~6 characters of garbage on boot. The port setting is 115200 baud, no parity, 8 bits, 1 stop. I have tried using PuTTY and HTerm. I have tried on a Linux box and a Win11 box. I have tried the stable release AM3352-SOM Debian image with kernel 3.12.10+ release 4‎ and received ~20k of garbage.

What else should I check?

[JohnS]

Maybe chars at the wrong baud rate until the new one is used?

John

[colinc]

Sorry John, I don't quite understand your response.

I did try different baud rates and configurations. The setup manual said the baud rate was 115200 with default parameters which I am assuming is no parity, 8 data bits and 1 stop bit. I am disconnecting, changing baud rate and other parameters, then reconnecting, then rebooting the EVM.

Also, I meant to say I was getting ~6k, not 6, garbage characters with the newer kernel on boot.

Anyway, thank you for replying John

[JohnS]

If you're getting lots then you should be able to figure the baud rate by trial and error (if you care).  A 'scope / logic analyser would make it much easier, though.

It may well be a much lower baud rate than you have perhaps tried.

John

[LubOlimex]

You say you have 6k and 20k of garbage on boot but does it mean that after the initial 6k and 20k of garbage you get normal output? Or is it just garbage?

Do you have GND of the serial cable connected to the board's GND? What is the flow control? Is the SOM board placed on the Olimex-made EVB board or stand-alone? Can you show us a picture of your hardware setup?