Rink, thanks for the thorough repose, I haven't had a chance to test it out but plan to very soon. In the meantime, I used the solution from this thread

http://gumstix.8.n6.nabble.com/Re-muxing-Overo-UART2-at-runtime-td638452.html

that was posted by Jesse. This has been working great and is done on boot and requires no building of the image, etc.

One word of caution is that I'm not sure if any processes are using ttyO2 on boot. Bluetooth has supposedly been turned off, however, I have a c++ program that uses the serial port and is set to run on boot, I often get errors when running at boot but not when running manually by logging in through ssh and running the program myself. I'm writing up a new thread for this problem and other serial issues as well. 

Thanks again! Will keep you posted. 

On Sun, Nov 11, 2012 at 4:25 PM, rink113 [via Gumstix] <[hidden email]> wrote:
QMay -

I also have been working through the scattered details of how to get UART 2 to be exposed to pins of the Gumstix Overo which are reffered to as GPIO 144-147 (146: TX, 147: RX, 144: CTS, 145: RTS) on various schematic diagrams and pinout tables. I just got it to work in the last hour (I actually subscribed to the list just so I could reply to your message). I got RX/TX working, I will try CTS and RTS soon (I need them). I found the following website very, very helpful with the detailed instructions you are looking for:

http://www.jumpnowtek.com/index.php?option=com_content&view=article&id=55&Itemid=61

The page guides you through how to use bitbake to build a patched u-boot. It also explains how to build u-boot from the cross-compilation tools using 'make' and the compilers directly. I will say this, I tried to use the bitbake way and make a patch -- I for some reason couldn't make it happen -- perhaps I didn't have something set up right. Ultimately, I ended up using the section that explains how to do it WITHOUT bitbake, modified the overo.h file directly, did the make commands as described, copied the u-boot over to my microsd, and my uart2 now works on the described pins.

I don't know if this is critical (sometimes u-boot uImage, the rootfs have to be synced?) but in my case I built all of the files MLO, u-boot, uImage, and the root file system using bitbake first, and after trying to do the patch with bitbake and failing to get UART 2 exposed, I built just u-boot without bitbake and copied that to the microsd. Mine is thankfully working.

I hope that helps. That website seems to have several Overo related "how-tos" that may be of use to you as well.

- rink113



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