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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], Ubuntu 10.04 with Linaro Toolchain, IGEP v2 RC5 and [http://svn.hylands.org/linux/gpio/ GPIO driver] wrote by Dave Hylands. There are more ways to use GPIOs in IGEP v2, but this one is simple and reliable.<br>

= Feedback There are more ways to use GPIOs. This article show two simple ways to use gpios: bash commandline and Contributing =C-code.

At any point, if you see a mistake you can contribute to For this How-ToI used [http://labs.<br> isee.biz/index.php/IGEP_firmware_Yocto IGEP firmware Yocto]

= Compile GPIO driver source code == Feedback and Contributing ===At any point, if you see a mistake you can contribute to this How-To. Edit yourself !

Download source code from author website using the next command:<br> == Requirements ==<pre>wget For this How-r -np httpto, I used://svn.hylands.org/linux/gpio/</pre> * IGEPv2 Board Due the source Makefiles are implemented * Only for Gumstix SDK, C-program example it is necessary change some constants for compile with our Hostalso needed:** Add shortcircuit cable between J990:20 and J990:22 pins. These constants By default, GPIO 156 (J990:20) and GPIO 157 (J990:22) are: available on these J990 pins.

In filesAnother boards tested:

Search lines: <pre>OVEROTOP ?= /home/gumstix/overoThe gpio-oeCROSS_COMPILE ?= $(OVEROTOP)/tmp/sysroots/x86_64int-linuxtest.c program shows one way of using the sysfs file /usrsys/armv7aclass/bin/arm-angstrom-linux-gnueabi-<gpio/pre> Replaced by your cross compiler path, for example: <pre>OVEROTOP ?= gpioXX/CROSS_COMPILE ?= $value to block program execution using poll(OVEROTOP)/usr/bin/arm-linux-gnueabi-</pre> In file:<br> until the input level on GPIOXX changes.

$/svn[[File:GPIO_TEST.hylands.org/linux/gpio/modules/Makefile<br> tar]]

Search lines== Bash commandline ==Basic gpio operations could be done using bash and sysfs : * Export GPIOs <pre>OVEROTOP ?= echo "GPIO number NN" > /homesys/gumstixclass/overo-oe#CROSS_COMPILE ?= $(OVEROTOP)gpio/tmpexport</cross/armv7a/bin/arm-angstrom-linux-gnueabi-pre>CROSS_COMPILE ?= $(OVEROTOP)** For example: '''echo "156" > /tmpsys/sysrootsclass/x86_64-linuxgpio/usr/armv7a/bin/arm-angstrom-linux-gnueabi-export'''<br><br>KERNEL_PATH &nbsp;?= ..* Unexport GPIOs <pre>echo "GPIO number NN" > /..sys/..class/..gpio/..unexport</gumstixpre> * Set GPIO direction <pre>echo "out" > /overo-oesys/tmpclass/sysrootsgpio/overo-angstrom-linux-gnueabigpioNN/kernelARCH ?= armdirection</pre> Replaced by your cross compiler path and your kernel source used path, for ** For example: <pre'''echo "out" >OVEROTOP ?= /#CROSS_COMPILE ?= $(OVEROTOP)sys/class/tmpgpio/crossgpio156/armv7adirection'''<br><br>* Set GPIO value <pre>echo "1" > /binsys/arm-angstrom-linux-gnueabi-CROSS_COMPILE ?= $(OVEROTOP)class/gpio/usrgpioNN/binvalue</arm-linux-gnueabi-pre>KERNEL_PATH &nbsp;?= ..* Get GPIO value <pre>cat /..sys/..class/..gpio/..gpioNN/&lt;your kernel source path used&gt;ARCH ?= armvalue</pre> Go to: $* Configure hardware interrupts <pre>echo "rising" > /svn.hylands.orgsys/linuxclass/gpio/Makefile and compile all source code downloaded using make command. gpioNN/edge<br/pre>

= Install binaries = C-program Example ==

Install binaries via root userC-program Example contains some C-functions to control 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:$/svn/labs.hylandsisee.org/linuxbiz/gpio/modules/ and insert user-gpio-drv.ko into linux kernel with the following command: <pre>insmod user-gpio-drvindex.ko<php/pre> Check that user-gpio-drvHow_to_setup_a_cross_compiler#Download.ko is currently loaded with the following command: <pre>lsmod</pre> The module is loaded until system halt2FInstall_IGEP_SDK Download an Install] IGEP SDK if you don't have it.

Go to* Download [http:$/svn/labs.hylandsisee.orgbiz/linuximages/gpio6/lib69/Gpio_examplebeta1. libgpio.so will be found heretar. bz2 source code]* Extract source code* Build source code:

You must tell to SO where the dynamic libraries Cross toolchain tools are. Now we define available into the environment variable LD_LIBRARY_PATH for SO can link a library with a program when a program make a callbuilt-in virtual machine Poky SDK. Type the follow commnadYou only need open bash terminal prompt and write command: <pre>export LD_LIBRARY_PATH=jdoe@ubuntu ~/root/svn.hylandsDesktop $ arm-poky-linux-gnueabi-gcc -o gpio_example gpio_examplebeta1.org/linux/gpio/lib/c</pre> === Execute app<br> ===

Go * Copy binary file to:$/svn.hylands.org/linux/gpio/app, gpio will be found here. IGEP Board

To make sure that libgpio.so can be founded as === Execute program ===Open a dependency of gpio remote terminal and locate your program binary, execute program use the following commandand pass like a parameter 157 value (GPIO 157): <pre> ldd gpio root@igep00x0:~# ./gpio_example 157 </pre> See if libgpio.so is found it. If you execute program in bash without linking library dependencies, bash give you a error messageResult will be:<pre>root@igep00x0:~# . /gpio_example 157gpio/direction: No such file or directory

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

<br>  '''Under construction'''<br> === Result ===At first remote terminal you should read a message similar like this:<brpre>  poll() GPIO 157 interrupt occurred <br/pre> Example:[[What can I do with IGEP0020#How_to_handle_the_gpio-LED.27s]]  [[Category:Work_in_progress]] [[Category:Communications]]