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= Overview=<brsection 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 How-To, 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 How-To was tested in: *[[IGEP firmware Yocto|IGEP firmware Yocto]] and [[Linux_Kernel_2.6.37.y|Kernel 2.6.37.y]] with IGEPv2.
= Preparing == Configure UART1 and UART3 in IGEP with RS232 levels on J960 connector ===
=== Configure UART1 and UART3 in IGEP with RS232 levels on J960 connector = Edit igep.ini file ====
To test UARTs we use UART1 (dev/ttyS0ttyO0) and UART3 (dev/ttyS2ttyO2) via J960 connector using RS232 standard.
=== Check UARTs devices ===
<pre>dmesg | grep tty</pre>
The result will be similar at that:
<pre>root@localhostigep00x0:~/PROGRAM# dmesg | grep tty
[ 0.000000] console [tty0] enabled
[ 0.598999485198] serial8250omap_uart.0: ttyS0 ttyO0 at MMIO 0x4806a000 (irq = 72) is a ST16654OMAP UART0[ 0.784057485565] serial8250omap_uart.1: ttyS1 ttyO1 at MMIO 0x4806c000 (irq = 73) is a ST16654OMAP UART1[ 0.969085485931] serial8250omap_uart.2: ttyS2 ttyO2 at MMIO 0x49020000 (irq = 74) is a ST16654OMAP UART2[ 10.153503486267] serial8250omap_uart.3: ttyS3 ttyO3 at MMIO 0x49042000 (irq = 80) is a ST16654root@localhost:~/PROGRAM# </pre> Get information about UARTs, type: <pre>setserial -g /dev/ttyS[0123]</pre> The result will be similar at that: <pre>root@localhost:~/PROGRAM# setserial -g /dev/ttyS*/dev/ttyS0, UART: 16654, Port: 0x0000, IRQ: 72/dev/ttyS1, UART: 16654, Port: 0x0000, IRQ: 73/dev/ttyS2, UART: 16654, Port: 0x0000, IRQ: 74/dev/ttyS3, UART: 16654, Port: 0x0000, IRQ: 80OMAP UART3root@localhostigep00x0:~/PROGRAM# </pre> If you don't have setserial installed type: <pre>apt-get install setserial</pre> NOTE: Starting from Kernel 2.6.37.y, ttySx are named ttyOx. You need to edit source program.
=== Connect peripherals ===
Connect IGEPv2 board using J960 connector like this:
<pre> J960
(Not used) x---| 1 2 |---o (Connect to 8)
(Connect to 9) o---| 3 4 |---x (Not used)
(Not used)x---| 7 8 |---o (Connect to 2)
(Connect to 3) o---| 9 10 |---x (Not used)
=== Send some data ===
Use minicom microcom to prove it, open two terminals via SSH and log with root user:
Terminal 1:
<pre>minicom -D microcom /dev/ttyS0ttyO0</pre>
Terminal 2:
<pre>minicom -D microcom /dev/ttyS2 ttyO2 </pre> Type something in one terminal. {| cellspacing="1" cellpadding="1" border="1" align="center" width="200"|-| style="text-align: left;" | [[Image:Minicom screenshot.png|640x400px]]|}
= Schematics =
=== Uart Schematic Igep Module ===
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| [[Image:Uart Schematic Igep Module.png|581x600px]]
= Compile and run program =
Download [http://downloadslabs.igepisee.esbiz/labsindex.php/uartFile: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 can be sent<br> chars sended.
Constant DEBUG: it can break program infinite loop part, it can be useful to debug some errors, : 0 (infinite loop) or positive number determine determines loop max entrances .
Constant WAIT: it configurea configures select max timein seconds.
Constants GPIO1 and GPIO2: they configure GPIOs used for debug via oscilloscope. Take care to configure By default, 158 and 162 values are not used in IGEPv2. Configure [[Mux configuration|mux and don't ]] properly if you use them for other purposes<br> GPIOs.
= Testing UART =
Decoded with [http://www.asciitable.com/ ASCII table].
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Program sends information via UART1 but don't receive response via UART3, because only a process is executed. This problem is repeated every 5 seconds (constant WAIT=5) until other process sends information via UART3 at the same speed. If "select" hasn't been implemented, process would have stayed blocked.<br>
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More information [http://en.wikipedia.org/wiki/RS-232#Standard_details here].
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Note that wave is degraded when speed is higher
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| [[Image:Uart 300 o.JPG|260x172px]]
You can see that RS232 have some lag between transmisions. This caused mainly by kernel process management. UART peripheral is controlled by Linux and It isn't a [http://en.wikipedia.org/wiki/Real-time_operating_system real-time operating system].
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This program have three I/O functions that connect to UART driver via ioctl: (read(), write() and select()). But select() and write() change process stat to sleep mode until system don't receive or transmit all information via UART. "select" function is used to prevent that read function can be blocked when data aren't available. <br>The next images (program with debug_gpio enabled and 300 bauds speed) show when process is executed or is waiting. Blue=UART1, Violet="write" and Green="select". When GPIO has HIGH value, process is blocked.<br>
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| [[Image:Uart select5.JPG|260x172px]]
Every full process the number is increased twice. Program checks that this condicion is true, if it isn't accomplished, process will be finish.
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