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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 [[Linux Kernel 2.6.35.y|Kernel 2.6.35.y]] source code. Extract files.<br>

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

We will use the ncurses program for set up Kernel configuration, if you don't have this program installed then you must install it with this command[[File: <pre>sudo apt-get install ncurses-dev </pre> -Go to kernel path and type: <pre>make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- menuconfig </pre> Exit Linux Kernel Configuration an return to Bash. Type: <pre>make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- modules_prepare&lt;br&gt; </pre> File $/include/generated/autoconfGPIO_TEST.h was created tar]]

Finally compile == Bash commandline ==Basic gpio operations could be done using bash and sysfs :* Export GPIOs <pre>echo "GPIO number NN" > /sys/class/gpio/export</pre>** For example: '''echo "156" > /sys/class/gpio/export'''<br><br>* Unexport GPIOs <pre>echo "GPIO number NN" > /sys/class/gpio/unexport</pre> * Set GPIO direction <pre>echo "out" > /sys/class/gpio/gpioNN/direction</pre>** For example: '''echo "out" > /sys/class/gpio/gpio156/direction'''<br><br>* Set GPIO value <pre>echo "1" > /sys/class/gpio/gpioNN/value</pre>* Get GPIO driver, go to main Makefile path and compile all source code using make command. value <pre>cat /sys/class/gpio/gpioNN/value</pre>* Configure hardware interrupts <pre>echo "rising" > /sys/class/gpio/gpioNN/edge</pre>

= Install binaries via IGEP<br> = C-program Example ==

Log with root user C-program Example contains some C-functions to install binariescontrol GPIOs. These also can do:* Export and unexport GPIOs* Set GPIO direction * Set GPIO value * Get GPIO value * Configure hardware interrupts

Go to=== Compile example program ===[http:$/modules and insert user-gpio-drv/labs.ko into linux kernel with the following command: <pre>insmod user-gpio-drvisee.ko<biz/pre> Check that user-gpio-drvindex.ko is currently loaded with the following command: <pre>lsmod</pre> The result will be similar at that: <br> <pre>root@localhost:~/gpio-driverphp/moduleHow_to_setup_a_cross_compiler# 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 </pre> The module is loaded until system haltDownload.2FInstall_IGEP_SDK Download an Install] IGEP SDK if you don't have it.

Go to* Download [http:$/lib/labs. libgpioisee.so is herebiz/images/6/69/Gpio_examplebeta1. tar.bz2 source code]* Extract source code* Build source code:

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 to the environment variable LD_LIBRARY_PATH, use Cross toolchain tools are available into the following command:<br> <pre>export LD_LIBRARY_PATH=/root/gpiobuilt-driver/lib/</pre> Check that libgpio.so is linked correctly. Go to:$/gpio-driver/app, gpio program is herein virtual machine Poky SDK. Type next You only need open bash terminal prompt and write command: <pre>ldd gpio </pre> ldd command, print shared library dependencies. The result will be similar at that: <pre>rootjdoe@localhost:ubuntu ~/gpioDesktop $ arm-poky-driver/app# ldd gpio libgpio.so =&gt; /root/gpiolinux-gnueabi-driver/lib/libgpio.so (0x40197000) libc.so.6 =&gt; /lib/libc.so.6 (0x401a0000) /lib/ldgcc -linuxo gpio_example gpio_examplebeta1.so.3 (0x4008a000)c</pre> The shared library is linked until system halt. Now you can execute gpio example program.

To make sure than driver works well=== Execute program ===Open a remote terminal and locate your program binary, make the next test. I used GPIO_136(sdmmc2_dat4) execute program and GPIO_137pass like a parameter 157 value (sdmmc2_dat5GPIO 157) because IGEP v2 RC5(without WIFI) don't use them by default: <pre>root@igep00x0:~# ./gpio_example 157 </pre>Result will be:<brpre> root@igep00x0:~# ./gpio_example 157gpio/direction: No such file or directory

'''NOTE:''' For more information visit this [[Mux configuration|page]]poll() GPIO 157 interrupt occurred............. <br/pre>

=== Configure Mux Generate interrupts ===Open a second remote terminal and type:<pre>cd /sys/class/gpio/echo 156 > export cd gpio156/ echo out > directionecho 0 > valueecho 1 > value</pre>

Go to:/sys/kernel/debug/omap_mux, and change 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 (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 Result === Link GPIO_136 and GPIO_137 with At first remote terminal you should read a wire, these pins are located in J990 connector with numbers 7 and 9. I use the next connector to join them:  <br>  [[Image:Connector used readwrite test.JPG|center|300x200px]][[Image:All connected readwrite test.JPG|center|300x200px]]<br>  <br>  <br>  <br>  <br>  <br>  <br>  <br>  <br>  Now type next codemessage similar like this: <pre>root@localhost:~/gpio-driver/app# ./gpio input 136root@localhost:~/gpio-driver/app# ./gpio output 137 0root@localhost:~/gpio-driver/app# ./gpio get 136 0root@localhost:~/gpio-driver/app# ./gpio output 137 1root@localhost:~/gpio-driver/app# ./gpio get 136 1root@localhost:~/gpio-driver/app# poll() GPIO 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:Communications]]