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__TOC__== Overview ==

This How-To is meant to be a starting point for people to learn use GPIOs for IGEP v2 devices as quickly and easily as possible. For this how-to i used [http://releases.linaro.org/platform/linaro-m/headless/final/linaro-m-headless-tar-20101108-2.tar.gz Linaro Headless] with [[Linux Kernel 2.6.35.y|Kernel 2.6.35.y]], Ubuntu 10.04 with Linaro Toolchain, IGEP v2 RC5 and GPIO driver (NOTE: Upload source code).

There are more ways to use GPIOs in IGEP v2, but this one is very . This article show two simpleways to use gpios: bash commandline and C-code.<br>

=== Feedback and Contributing ===At any point, if you see a mistake you can contribute to this How-To.<br> Edit yourself !

= Compile = Requirements ==For this How-to, I used:* IGEPv2 Board * Only for C-program example it also needed:** Add shortcircuit cable between J990:20 and J990:22 pins. By default, GPIO driver source code via Host<br> =156 (J990:20) and GPIO 157 (J990:22) are available on these J990 pins.

Download GPIO driver (NOTEAnother boards tested:Upload source code) and with [[Linux Kernel 2.6.35.y|Kernel 2.6.35.y]] source code. Extract files.<br>

In The gpio-int-test.c program shows one way of using the sysfs file: $/modulessys/class/gpio/Makefile, make sure that your CROSS_COMPILE path is correct and&nbsp;type your Kernel 2.6.35.y pathgpioXX/value to block program execution using poll() until the input level on GPIOXX changes.<br>

Log with root user Example program configures a GPIO to install binarieswait a hardware interrupt. Once the GPIO value change from 0 value to 1 value (rising), program gives you a message.

=== Install module Compile example program ===[http://labs.isee.biz/index.php/How_to_setup_a_cross_compiler#Download.2FInstall_IGEP_SDK Download an Install] IGEP SDK if you don't have it.

Go First of all you need to:$/svn.hylands.org/linux/gpio/modules/ and insert user-gpio-drv.ko into linux kernel with initialize a suitable environment in the following command: <pre>insmod user-gpio-drvbash shell console inside your machine.ko</prebr> Check that user-gpioYou can do this sourcing once the environment-drvsetup script.ko is currently loaded with the following command: <pre>lsmod</pre> The result will be similar at that: <br> <pre>rootjdoe@localhost:ubuntu ~$ source /opt/poky/svn.hylands1.org2/environment-setup-armv7a-vfp-neon-poky-linux/gpio/module# lsmodModule Size Used byuser_gpio_drv 1639 0 omap_wdt 3411 0 spidev 4198 0 iommu 8558 0 rtc_twl 4411 0 rtc_core 11187 1 rtc_twltwl4030_keypad 2970 0 -gnueabi </pre> The module is loaded until system halt.

Go toCross toolchain tools are available into the built-in virtual machine Poky SDK. You only need open bash terminal prompt and write command:<pre>jdoe@ubuntu ~/Desktop $/svnarm-poky-linux-gnueabi-gcc -o gpio_example gpio_examplebeta1.hylands.org/linux/gpio/libc</. libgpio.so is here. pre>

If a program is linked with shared libraries, Kernel seek in specific paths when program is executed. Now is necessary link the libgpio.so path * Copy binary file to the environment variable LD_LIBRARY_PATH, use the following command:<br> <pre>export LD_LIBRARY_PATH=/root/svn.hylands.org/linux/gpio/lib/</pre> Check that libgpio.so is linked correctly. Go to:$/svn.hylands.org/linux/gpio/app, gpio program is here. Type next command: <pre>ldd gpio </pre> ldd command, print shared library dependencies. The result will be similar at that: <pre>root@lSee if libgpio.so is found it. If you execute program in bash without linking library dependencies, bash give you a error message. ocalhost:~/svn.hylands.org/linux/gpio/app# ldd gpio libgpio.so =&gt; /root/svn.hylands.org/linux/gpio/lib/libgpio.so (0x40197000) libc.so.6 =&gt; /lib/libc.so.6 (0x401a0000) /lib/ld-linux.so.3 (0x4008a000)</pre> The shared library is linked until system halt. Now you can execute gpio example program.IGEP Board

= Testing driver == Execute program ===Open a remote terminal and locate your program binary, execute program and pass like a parameter 157 value (GPIO 157):<pre>root@igep00x0:~# ./gpio_example 157 </pre>Result will be:<pre>root@igep00x0:~# ./gpio_example 157gpio/direction: No such file or directory

To make sure than driver works well, make the next test. I used GPIO_136poll(sdmmc2_dat4) and GPIO_137(sdmmc2_dat5) because IGEP v2 RC5(without WIFI) don't use them by default: GPIO 157 interrupt occurred............. <br/pre>

'''NOTE=== Generate interrupts ===Open a second remote terminal and type:''' For more information visit this [[Mux configuration|page]]. <brpre>cd /sys/class/gpio/echo 156 > export cd gpio156/ echo out > directionecho 0 > valueecho 1 > value</pre>

=== Configure Mux Result === Go to:/sys/kernel/debug/omap_mux, and change At first remote terminal you should read a message similar like this mux configuration: <pre>echo 0x104&gt;sdmmc2_dat4echo 0x104&gt;sdmmc2_dat5</pre> Use cat command to check it:<br> <pre>cat sdmmc2_dat4cat sdmmc2_dat5</pre> The result will be similar at that: <pre>root@localhost:/sys/kernel/debug/omap_mux# cat sdmmc2_dat4name: sdmmc2_dat4.gpio_136 (0x48002164/0x134 = 0x0104), b ae4, t NAmode: OMAP_PIN_INPUT | OMAP_MUX_MODE4signals: sdmmc2_dat4 | sdmmc2_dir_dat0 | NA | sdmmc3_dat0 | gpio_136 | NA | NA | safe_mode</pre> and <pre>root@localhost:/sys/kernel/debug/omap_mux# cat sdmmc2_dat5name: sdmmc2_dat5.gpio_137 poll(0x48002166/0x136 = 0x0104), b ah3, t NAmode: OMAP_PIN_INPUT | OMAP_MUX_MODE4signals: sdmmc2_dat5 | sdmmc2_dir_dat1 | cam_global_reset | sdmmc3_dat1 | gpio_137 | hsusb3_tll_stp | mm3_rxdp | safe_mode</pre> Note: OMAP_PIN_INPUT=Input/Output pin and OMAP_PIN_OUTPUT=Output pin, for Read/Write test you need the first one. GPIO is configured in mode 4.<br> === Read/Write test === Link GPIO_136 and GPIO_137 with a wire, these pins are located in J990 connector with numbers 7 and 9. Now type next code: <pre>root@localhost:~/svn.hylands.org/linux/gpio/app# ./gpio input 136root@localhost:~/svn.hylands.org/linux/gpio/app# ./gpio output 137 0root@localhost:~/svn.hylands.org/linux/gpio/app# ./gpio get 136 0root@localhost:~/svn.hylands.org/linux/gpio/app# ./gpio output 137 1root@localhost:~/svn.hylands.org/linux/gpio/app# ./gpio get 136 1root@localhost:~/svn.hylands.org/linux/gpio/app# 157 interrupt occurred </pre> The code above shows that driver works properly, GPIO_136 is configured like input and GPIO_137 is configured like output with value 0, when read GPIO_136 the result is 0. To make sure that works well, configure GPIO_137 with value 1, now GPIO_136 reads 1. <br> This driver have more options like IRQ, but is not explained here. <br> Other examples:[[What can I do with IGEP0020#How_to_handle_the_gpio-LED.27s]]  [[Category:Work_in_progress|Work_in_progress]] [[Category:Communications]]