Yesterday, I received beaglebone and PL2303HX USB to TTL serial cable I ordered few weeks a go. First thing I tried to do with the beaglebone was to try it's serial port.
So I connected the serial cable with the beaglebone and PC. I use fedora on my PC, so I used screen program to communicate with the serial port.
Then I powered up the beaglebone using the mini USB port and was waiting for the messages to be printed in the serial console.
Well, the good news was that messages were printed. but there were bad news.
sometimes it showed garbled messages. Also when it showed messages correctly, I wasn't able to type. It was simply a read only screen session.
What went wrong? I started googling and couldn't find any clue. finally I landed on a page where it lists beaglebone HW faults and it listed a similar scenario described as a HW fault. But it was a very old issue and cannot believe it still exists in new boards.
So I started diagnosing the issue.
First I tried to check whether it is an issue with the PC. Therefore I connected the beaglebone and the serial cable setup with my windows laptop. I did't get garbled messages on my screen session this time (I used Putty) but still I couldn't type.
So this must be an issue with either the beaglebone or the serial cable. If it's an issue with the beaglebone, I do not have any option. So I decided to diagnose the serial cable. I opened the USB side of the cable to check the circuit. the USB side can be easily opened since it was not sealed.
Huh, Found the issue!!!. The green wire was detached from the PCB due to a bad soldering job.
I soldered the green wire to the PCB again and reconnected the setup with the PC.
voila, screen session is bidirectional now. :)
