How to: UART Angstrom

Hi everyone,

Thank you for taking the time to read this.

I'm a newbie to the whole linux operating systems, for which I am
seeking some advice on how to get the UART on the header pins up and
running so I can communicate to another board I have.

Now, according to the BB datasheet the pins I am required to use are
multiplexed on pins 4, 10, 8 & 6.

Where do I need to look to be able to change the multiplexer to these
pin configurations?

Are there pre-built drivers in Angstroms Linux for the UART? If so,
how would I go about using this?

My device used the 8, N, 1 configuration at 4800 baud.

Any advice to get me started would be greatly appreciated.

Thank you again for your time and I look forward to any responses.

Hi everyone,

Thank you for taking the time to read this.

I'm a newbie to the whole linux operating systems, for which I am
seeking some advice on how to get the UART on the header pins up and
running so I can communicate to another board I have.

Now, according to the BB datasheet the pins I am required to use are
multiplexed on pins 4, 10, 8 & 6.

Where do I need to look to be able to change the multiplexer to these
pin configurations?

Program the pinmux. You can do this in U-boot or Linux. There seems be a
problem with the current kernel pinmux setup code. But if you want to see
what's that involve with doing it the kernel method, I have a write up. But
note that this does seem to work with the current kernel (2.628/2.6.29).

http://www.hy-research.com/beagle_expansion.html

It may be obvious but those pins are all at 1.8V so you will almost always
need a level converter unless you have other 1.8V logic on the other side.
Not sure if it helps but I wrote up what I did to use the UART.

The only other gotcha is to make sure you only enable the UART RX and TX
for the ball that is routed to the expansion header. Otherwise, TX will work
but RX won't.

Are there pre-built drivers in Angstroms Linux for the UART? If so,
how would I go about using this?

Standard L-O kernel has that UART setup ready to go. So you shouldn't
need anything other then reprogramming the pinmux.

Hope this helps.

Very useful and very well explained thank you Hunyue.

I do have a logic level converter in the post on its way to me, but
thanks for the tip :-).

I will have a read through your beagle_expansion.html report and if I
come across any problems I will post back here again.

Thank you for your time my friends, it is greatly appreciated.

Rob

Sorry google code had me logged in as my other user. It was me Hurdy
who replied to you :slight_smile: heheh