On Oct 23, 2005, at 6:45 PM, Andrey Gleener wrote:

I found your Email on Bulletin Board. Decided to write directly to you – it is not clear from the Web pages how to ask for support.

Hi Andrey.  Emailing me directly works :)  The best way to ask questions though is via the mailing list, which you can sign up for at http://sf.net/projects/gumstix -- out of curiosity, and so we can help other customers in the future find that out more easily, where did you look for info?  We can add a link or explanation anywhere on the site if it would make sense to you to see something somewhere it's not currently -- if that clause makes any sense.

Also, I'm cc'ing your questions and my answers to the mailing list, so that they'll make it into the list archives for future searchers.

I am trying to make use of HWUART and can not seemingly make it working. I do simple thing: using Minicom program set it so there is no flow control and expect to see pulses coming out of pin 33 or 35 of 60-pin Connector when I press keyboard keys. It does not. The Wiki discussions are very confusing.

minicom on the host side, or on the gumstix side?  I'm not sure I understand your setup?  Are you logged into the gumstix through either console or a network link, then running a comms program on the gumstix and watching pins 33/35 using a meter/scope?

Can you please describe what to do to make it work?
  1. Which line is the output – pin 33 or pin 35 of 60 pin connector?
http://www.gumstix.org/tikiwiki/tiki-index.php?page=I%2FO describes the connector -- you've probably already found that since you seem to know the pin numbers.  TX/RX on that chart is from the gumstix's point of view, so the gumstix sends on TX (35) and reads from RX (33).  On the connector, those signals are TTL (3.3V), not RS232.
  1. I use Gumstix Connex with Bluetooth with Etherstix Board attached. Is the HWUART still available for me?
I don't think so -- I believe that the ethernet controller requires the nPWE signal from the PXA on GPIO line 49, which is the same as the HWUART RxD signal.  Also, HWUART is used to control the bluetooth module (on different lines, HWUART for bluetooth can work at the same time as the ethernet).
  1. How to set Tx and Rx lines to be Serial output and input, not GPIO?
Page 4-4 of the Intel PXA255 Developer's Manual shows what the ALT mode of the various GPIO lines ought to be for different functions.  To set up a mode on the gumstix, you can do:

modprobe proc_gpio
echo AF1 out > /proc/gpio/GPIO48

for example -- that sets line 48 to alt-function 1 out.  Note though that if you alter GPIO49 from AF2 out to something else, ethernet will misbehave.
  1. What exactly to do to disable flow control? (I am planning to use TX and RX lines only.)
If you're writing your own code, then use termios controls to disable flow control.  If you're using a terminal program, disable flow control however that implements it.  If you're just reading/writing the /dev/ttyS* device with a program which doesn't use termios to change the serial port settings, then you can use the stty program to alter the device's settings before or during that program running.
  1. Is anything else required to make this serial port operational?
Nope -- shouldn't be.  I think the problem you're running into though is most likely that the HWUART isn't available on the 60-pin connector when you're using bluetooth or ethernet.

We are in the process of revising the gumstix boards to bring the lines which go to the bluetooth module out over the 60-pin connector as well, but since you're using bluetooth, that won't actually help you much -- you're going to be limited to just the FFUART and the STUART when using bluetooth and ethernet.