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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 IGEP = 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[0123]/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>
=== 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)
</pre>
=== 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 =
<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.
= 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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| [[Image:Uart select timeout9.JPG|350x230px]]
More information [http://en.wikipedia.org/wiki/RS-232#Standard_details here].
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| [[Image:Uart voltageparams8.JPG|350x230px]]
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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| [[Image:Uart error test2.png|640x400px]]
<br>
[[Category:Communications]] [[Category:How_to_forge]] [[Category:TutorialsUART]]