KaiDaniel wrote:

>

> Hello,

>

> regarding the expansion board "summit" for the Overo GumStix I have

> got a

> question: Where can I find a serial port connector (RS232/UART)?

>

> 2x 2-wire serial ports are announced at:

> http://www.gumstix.com/store/catalog/product_info.php?cPath=31&product

> s_id=215

>

> The 40-pin header is described under:

> http://www.gumstix.net/Hardware/view/Hardware/Summit-board-40-pin-head

> er/112.html

>

> But there is no further explanation. So I like to know, if there are a

> pins for a serial communication according to RS232/UART protocol.

>

> Thank you in advance for answering.

>

> BR,

> Kai

>

 

I have just been going through this exercise myself, and here is what I've found:

 

Information on using Overo serial ports:

 

Connections for the serial ports on the Overo are available on the 40-pin Summit board header:

http://www.gumstix.net/Hardware/view/Hardware/Summit-board-40-pin-header/112.html

They are:

UART 1 (/dev/ttyS0): pins 9 and 10 (these are connected to pins 24 and 48 of the 70-pin J4 connector)

UART 3 (/dev/ttyS2): pins 21 and 22 (these are connected to pins 26 and 31 of the 70-pin J1 connector)

 

For reference, the 70-pin J1 and J4 connector pin-outs are available at:

http://www.gumstix.net/Hardware/cat/Motherboard-I/O/112.html

 

There is also a third serial port available (UART 2, /dev/ttyS1), but it is slated for use with Bluetooth.  The first Nabble posting URL I include below discusses a workaround that shows how to use this third serial port.

 

A couple good postings about using serial on Overo:

http://www.nabble.com/Using-UART-2-on-an-Overo-td22534595.html

http://www.nabble.com/serious-OVERO-%2B-SUMMIT-IO%2C-opkg-and-TPS65950-questions-td22175411.html

 

A couple sections from this second Nabble posting are listed here for reference:

 

=========================

 

Using the UART is as simple as it is in any other Linux distro - simply open /dev/ttyS0.  If you don't know how, Google it - there are several Linux serial port how-to's that do a great job of describing it.  The two wire ports, while I'm not sure exactly what byte order, format etc it's expecting things in, can be found at /dev/i2c-1.  You should be able to access GPIO through devices in the /sys/class/gpio folder.

 

Make sure you level shift from 1.8V logic - I've found Sparkfun's logic level converters to be invaluable for prototyping:

http://www.sparkfun.com/commerce/product_info.php?products_id=8745

 

Hope this helps - I'm really not too much further than you are.  While I'll second the lamentation that the documentation is virtually non-existent, I've used other Linux boards and the learning process is much the same.  You have to expect this when diving into the embedded Linux world!

 

========================

 

One thing you must realize is that everything on a linux system becomes a file , just have a look in /dev/ Once someone has written a driver for a device is usually shows up on /dev/(SOMEPATH).

You can look at some of the older i2c-io code that reads and writes to the i2c bus, very strait forward.

Quick and dirty way to get to things

f = open("/dev/blah","r") ;

ioctrl(something);

 

I ended up doing this for a honeywell compass . I had to have two file hands one for writing and one for reading.

 

=======================

 

Since Overo uses 1.8V logic, a voltage level translator will be required for many applications.  Two such units that I saw referenced are:

TI’s TXB0104

(http://www.nabble.com/Overo-and-robotics-td20636287.html#a20765902,

http://focus.ti.com/docs/prod/folders/print/txb0104.html)

 

Sparkfun’s Logic Level Converter (referenced in the second Nabble URL above,

http://www.sparkfun.com/commerce/product_info.php?products_id=8745)