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How to use UARTs

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'''UNDER MAINTENANCE'''

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= Overview =

<section begin=overview />

This How-To is meant to be a starting point for people to learn use UART for IGEP devices as quickly and easily as possible. In this howHow-toTo, we use [http://labs.isee.biz/index.php/Pre-installed_software_on_IGEP_Processor_Boards IGEP Firmware] and a program that use UART peripherals. This program How-To was tested in: *[[IGEP firmware Yocto|IGEP firmware Yocto]] with and [[Linux_Kernel_2.6.37.y|Kernel 2.6.37.y]]with IGEPv2.

These example Example program has a debug option using GPIOs to debug via oscilloscope, this method is useful to learn about the Kernel latencies. Debug has set to "write" and "select" functions. More information: [[Peripherals Summary#UART|More information about ]].

<section end=overview />

= Preparing IGEP =

IGEP Uart devices have the following names in Kernel [[Linux Kernel 2.6.35.y|2.6.35.y]]:

*UART1: /dev/ttyS0

*UART2: /dev/ttyS1

*UART3: /dev/ttyS2

*UART4: /dev/ttyS3

IGEP Uart devices have the following names in Kernel [[Linux Kernel 2.6.37.y|2.6.37.y]]:

*UART1: /dev/ttyO0

*UART2: /dev/ttyO1

*UART3: /dev/ttyO2

*UART4: /dev/ttyO3

 

=== Configure UART1 and UART3 in IGEP with RS232 levels on J960 connector ===

;console=ttyO</pre>

==== Edit inittab file ====

Getty program uses /dev/ttyO2 in IGEP Firmware, disable it modifying /devetc/inittab file:*Comment nest next line:

<pre> #S:2345:respawn:/sbin/getty 115200 ttyO2</pre>

= Compile and run program =

Download [http://labs.isee.biz/images/e/eeindex.php/File:Uart-test-beta22-beta1.tar.bz2 program source]and extract it.  As explained above, Before compiling the program uses GPIO for debug option via oscilloscope, it is necessary install user-gpio-drv.ko driver inside Linux Kernel, more information [[How to use GPIOs|here]] .  There there are some interesting things to configure, before compiling the program. Open it, program and seek next lines:

<pre>//Define Array char size

#define SIZE 30

 

//Define Debug mode:0==Disable

#define DEBUG 0

//Set GPIO Debugger port

//Be sure that mux is correctly configured and GPIOs are not used

#define GPIO1 136158#define GPIO2 137 162</pre> Constant SIZE: it determines the max number of char than chars sended. Constant DEBUG: it can be sent<br> break program infinite loop part, useful to debug errors: 0 (infinite loop) or positive number determines loop max entrances.

Constant DEBUGWAIT: it can break program infinite loop part, it can be useful to debug some errors, 0 (infinite loop) or positive number determine loop configures select max entrances time in seconds.

Constant WAITConstants GPIO1 and GPIO2: it configurea select max timethey configure GPIOs used for debug via oscilloscope. By default, 158 and 162 values are not used in IGEPv2. Configure [[Mux configuration|mux]] properly if you use other GPIOs.

Constants GPIO1 and GPIO2Compile source code using a [[How to setup a cross compiler|cross compiler]] for example IGEP SDK: they configure GPIOs used for debug via oscilloscope<pre>arm-poky-linux-gnueabi-gcc uart-test-2-beta1. Take care to configure mux and don't use them for other purposesc -o uart-test-beta1 <br/pre>

Once you have installed module. Compile program using your Cross Compiler, I used arm-linux-gnueabi-:

<pre>arm-linux-gnueabi-gcc uart-test-beta1.c -o uart-test-beta1 </pre>

= Testing UART =

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