I'm somewhat disappointed with the BeagleBone's USB based serial port setup to connect to a host PC. I've written about some of my frustration before, but it's only getting worse for me.

Now, sometimes (although not that often) when I plug the mini-USB cable into the BeagleBone while holding the reset button (to prevent booting) and open my serial terminal, when I release the reset I get garbage on the terminal and the Bone won't boot. Resetting the board a few times often fixes this, but is very annoying. Also, sometimes if I already have the Bone running with external power and then attempt to connect the mini-USB cable, I still sometimes get garbage in the terminal.

I'm not sure of the root cause, but it affects at least one of the BeagleBones I have on my desk (I have 3 total). It could very well be that minicom is somewhat to blame, I'm switching to picocom to see if that helps. Regardless, I'm now very much desiring a real serial port that avoids this whole FTDI chip business. It'd be nice to have a "real serial port cape" that provides DB9 connectors for one or two of the serial ports that are exposed through the expansion headers. Modifying the SPL, u-boot, and kernel to use a different UART isn't hard...

The main issue would be getting the boot loaders to read the cape I2C memory and realize that it should change the default UART output automatically. That's doable if people are willing to rebuild the bootloader (or download a precompiled version) and use it. It would be handy if the default BeagleBone bootloader supplied with the kit did this, but maybe that's asking a bit much. I should probably write up this idea on the BeagleBoard mailing list...

I think the goal of having one connection for USB, JTAG, and power was a good goal for the BeagleBone team. It's just that I don't really want that. Apparently I'm special :). Otherwise I do really like the BeagleBone. I'd personally prefer a real RS232 levels serial port, external power adapter (or PoE!), and a JTAG header (dedicated FTDI JTAG devices are under $100 from many vendors).


I'm personally not a fan of screen for serial terminals. The scrollback isn't intuitive for me (my problem, not necessarily screen's as it can be changed in the config). I will give it a try the next time minicom or picocom barf.

I've never had any issues using minicom for real serial ports (think /dev/ttyS0 and friends) or dedicated USB to serial port devices that have a DB9 connector. I've been having issues here and there with the integrated system on the BeagleBone. Because of my past good experiences, it makes me think the Bone is the problem, not me (but I'm slightly biased).

sudo screen /dev/ttyUSB1 115200,cs8,-ixon,-ixoff


13 January 2012