Limit to serial connection speed?

I’m trying to use a BBB Rev C running Debian to connect to UART4 (ttyO4) at a 1000000 baud, but I can’t make it work. The device I’m connecting to requires it to be that high. I tried a different device that works at I’m a Windows guy that’s knee deep in Linux and ankle deep in embedded Linux. I’ve got another device that runs at 460800 (UART1 ttyO1 if that matters) which works fine, so I’m starting to think it has something to do with the speed.

I’ve read a lot of posts that suggest that the 3.8 kernel can’t support it, but that it might be “easy” to change, but after that I lose track of what folks are talking about (specifically this post:!topic/beagleboard/EEe7xAkCPkQ). As I read it, the 3.11 kernel supports higher speeds, but it’s not supported on the BBB. I’m a Windows guy that’s knee deep in Linux and ankle deep in embedded, so this is not in my wheelhouse (but fun to learn).

The bottom line here is: can I connect to hardware at 1000000 baud on the BBB running Debian Wheezy? If not out of the box is there a way to make it work without running an unsupported kernel on it?


Baud rates need to be in a multiple of the clock rate. Would 921600 work
? how about 1382400 ?

Remember the highest supported baud rate is 3686400 (AM335X Technical
Reference Manual, Table 19-6).

But most driver chips like max232 can only handle 1mbps so at higher
baud rates you might only get ttl level signals
to go that high of a speed. Depending on the length of your wires you
may need differential signaling as well (rs485)