Difference between revisions of "How to use GPIOs"

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= Overview  =
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__TOC__
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== Overview  ==
  
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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>
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This How-To is meant to be a starting point for people to learn use GPIOs for IGEP devices as quickly and easily as possible.  
  
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= Feedback and Contributing  =
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There are more ways to use GPIOs. This article show two simple ways to use gpios: bash commandline and C-code.
  
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At any point, if you see a mistake you can contribute to this How-To.<br>
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For this How-To I used [http://labs.isee.biz/index.php/IGEP_firmware_Yocto IGEP firmware Yocto]
  
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= Compile GPIO driver source code =
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=== Feedback and Contributing ===
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At any point, if you see a mistake you can contribute to this How-To. Edit yourself !
  
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Download source code from author website using the next command:<br>
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== Requirements ==
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<pre>wget -r -np  http://svn.hylands.org/linux/gpio/
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For this How-to, I used:
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</pre>
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* IGEPv2 Board
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Due the Makefiles are wrote for Gumstix SDK, it is necessary change some constants to our Host. There are:
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* Only for C-program example it also needed:
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** Add shortcircuit cable between J990:20 and J990:22 pins. By default, GPIO 156 (J990:20) and GPIO 157 (J990:22) are available on these J990 pins.
  
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$/svn.hylands.org/linux/gpio/app/Makefile
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Another boards tested:
  
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$/svn.hylands.org/linux/gpio/lib/Makefile
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*IGEP COM MODULE
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*IGEP COM AQUILA
  
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Search lines:
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== How to chek an GPIO ==
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<pre>OVEROTOP ?= /home/gumstix/overo-oe
 
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CROSS_COMPILE ?= $(OVEROTOP)/tmp/sysroots/x86_64-linux/usr/armv7a/bin/arm-angstrom-linux-gnueabi-
 
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</pre>
 
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Replace by, your cross compiler path, for example:
 
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<pre>OVEROTOP ?= /
 
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CROSS_COMPILE ?= $(OVEROTOP)/usr/bin/arm-linux-gnueabi-
 
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</pre>
 
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$/svn.hylands.org/linux/gpio/modules/Makefile<br>
 
  
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Search lines:
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The gpio-int-test.c program shows one way of using the sysfs file /sys/class/gpio/gpioXX/value to block program execution using poll() until the input level on GPIOXX changes.
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<pre>OVEROTOP ?= /home/gumstix/overo-oe
 
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#CROSS_COMPILE ?= $(OVEROTOP)/tmp/cross/armv7a/bin/arm-angstrom-linux-gnueabi-
 
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CROSS_COMPILE ?= $(OVEROTOP)/tmp/sysroots/x86_64-linux/usr/armv7a/bin/arm-angstrom-linux-gnueabi-
 
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KERNEL_PATH    &nbsp;?= ../../../../../gumstix/overo-oe/tmp/sysroots/overo-angstrom-linux-gnueabi/kernel
 
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ARCH ?= arm</pre>
 
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Replace by, your cross compiler path and your kernel source path used, for example:
 
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<pre>OVEROTOP ?= /
 
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#CROSS_COMPILE ?= $(OVEROTOP)/tmp/cross/armv7a/bin/arm-angstrom-linux-gnueabi-
 
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CROSS_COMPILE ?= $(OVEROTOP)//usr/bin/arm-linux-gnueabi-
 
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KERNEL_PATH    &nbsp;?= ../../../../../&lt;your kernel source path used&gt;
 
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ARCH ?= arm</pre>
 
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Go to: $/svn.hylands.org/linux/gpio/Makefile and compile app, lib and module using make command.  
 
  
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Transfer binaries created to IGEP v2
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[[File:GPIO_TEST.tar]]
  
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= Install binaries =
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== Bash commandline ==
 +
Basic gpio operations could be done using bash and sysfs :
 +
* Export GPIOs <pre>echo "GPIO number NN" > /sys/class/gpio/export</pre>
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** For example: '''echo "156" > /sys/class/gpio/export'''<br><br>
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* Unexport GPIOs  <pre>echo "GPIO number NN" > /sys/class/gpio/unexport</pre>
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* Set GPIO direction <pre>echo "out" > /sys/class/gpio/gpioNN/direction</pre>
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** For example: '''echo "out" > /sys/class/gpio/gpio156/direction'''<br><br>
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* Set GPIO value <pre>echo "1" > /sys/class/gpio/gpioNN/value</pre>
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* Get GPIO value  <pre>cat /sys/class/gpio/gpioNN/value</pre>
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* Configure hardware interrupts <pre>echo "rising" > /sys/class/gpio/gpioNN/edge</pre>
  
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=== Install module  ===
 
  
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Go to:$/svn.hylands.org/linux/gpio/modules/ and insert user-gpio-drv.ko into linux kernel with the following command:
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== C-program Example ==
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<pre>insmod user-gpio-drv.ko
 
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</pre>
 
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Check that user-gpio-drv.ko is currently loaded with the following command:
 
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<pre>lsmod</pre>
 
  
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The module is loaded until system halt.
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C-program Example contains some C-functions to control GPIOs. These also can do:
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* Export and unexport GPIOs
 +
* Set GPIO direction
 +
* Set GPIO value
 +
* Get GPIO value
 +
* Configure hardware interrupts
  
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=== Install dynamic library  ===
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Example program configures a GPIO to wait a hardware interrupt. Once the GPIO value change from 0 value to 1 value (rising), program gives you a message.
  
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<br>
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=== Compile example program ===
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[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.
  
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=== Execute app  ===
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First of all you need to initialize a suitable environment in the bash shell console inside your machine. <br> You can do this sourcing once the environment-setup script.
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<pre>jdoe@ubuntu ~ $ source /opt/poky/1.2/environment-setup-armv7a-vfp-neon-poky-linux-gnueabi </pre>
  
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<br>
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* Download [http://labs.isee.biz/images/6/69/Gpio_examplebeta1.tar.bz2 source code]
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* Extract source code
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* Build source code:
  
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= Testing driver  =
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Cross toolchain tools are available into the built-in virtual machine Poky SDK. You only need open bash terminal prompt and write command:
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<pre>jdoe@ubuntu ~/Desktop $ arm-poky-linux-gnueabi-gcc -o gpio_example gpio_examplebeta1.c</pre>
  
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<br>
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* Copy binary file to IGEP Board
  
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<br> Example:[[What can I do with IGEP0020#How_to_handle_the_gpio-LED.27s]]
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=== Execute program ===
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Open a remote terminal and locate your program binary, execute program and pass like a parameter 157 value (GPIO 157):
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<pre>root@igep00x0:~# ./gpio_example 157 </pre>
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Result will be:
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<pre>root@igep00x0:~# ./gpio_example 157
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gpio/direction: No such file or directory
  
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[[Category:Work_in_progress]] [[Category:Communications]]
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poll() GPIO 157 interrupt occurred
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............. </pre>
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=== Generate interrupts ===
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Open a second remote terminal and type:
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<pre>cd /sys/class/gpio/
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echo 156 > export
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cd gpio156/
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echo out > direction
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echo 0 > value
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echo 1 > value</pre>
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=== Result ===
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At first remote terminal you should read a message similar like this:
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<pre>poll() GPIO 157 interrupt occurred </pre>

Latest revision as of 16:59, 22 September 2015

Overview

This How-To is meant to be a starting point for people to learn use GPIOs for IGEP devices as quickly and easily as possible.

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

For this How-To I used IGEP firmware Yocto

Feedback and Contributing

At any point, if you see a mistake you can contribute to this How-To. Edit yourself !

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 156 (J990:20) and GPIO 157 (J990:22) are available on these J990 pins.

Another boards tested:

  • IGEP COM MODULE
  • IGEP COM AQUILA

How to chek an GPIO

The gpio-int-test.c program shows one way of using the sysfs file /sys/class/gpio/gpioXX/value to block program execution using poll() until the input level on GPIOXX changes.

File:GPIO TEST.tar

Bash commandline

Basic gpio operations could be done using bash and sysfs :

  • Export GPIOs 
    echo "GPIO number NN" > /sys/class/gpio/export
    • For example: echo "156" > /sys/class/gpio/export

  • Unexport GPIOs 
    echo "GPIO number NN" > /sys/class/gpio/unexport
  • Set GPIO direction 
    echo "out" > /sys/class/gpio/gpioNN/direction
    • For example: echo "out" > /sys/class/gpio/gpio156/direction

  • Set GPIO value 
    echo "1" > /sys/class/gpio/gpioNN/value
  • Get GPIO value 
    cat /sys/class/gpio/gpioNN/value
  • Configure hardware interrupts 
    echo "rising" > /sys/class/gpio/gpioNN/edge


C-program Example

C-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

Example program configures a GPIO to wait a hardware interrupt. Once the GPIO value change from 0 value to 1 value (rising), program gives you a message.

Compile example program

Download an Install IGEP SDK if you don't have it.

First of all you need to initialize a suitable environment in the bash shell console inside your machine.
You can do this sourcing once the environment-setup script. 

jdoe@ubuntu ~ $ source /opt/poky/1.2/environment-setup-armv7a-vfp-neon-poky-linux-gnueabi
  • Download source code
  • Extract source code
  • Build source code:

Cross toolchain tools are available into the built-in virtual machine Poky SDK. You only need open bash terminal prompt and write command: 

jdoe@ubuntu ~/Desktop $ arm-poky-linux-gnueabi-gcc -o gpio_example gpio_examplebeta1.c
  • Copy binary file to IGEP Board

Execute program

Open a remote terminal and locate your program binary, execute program and pass like a parameter 157 value (GPIO 157): 

root@igep00x0:~# ./gpio_example 157

Result will be: 

root@igep00x0:~# ./gpio_example 157
gpio/direction: No such file or directory

poll() GPIO 157 interrupt occurred
.............

Generate interrupts

Open a second remote terminal and type: 

cd /sys/class/gpio/
echo 156 > export 
cd gpio156/ 
echo out > direction
echo 0 > value
echo 1 > value

Result

At first remote terminal you should read a message similar like this: 

poll() GPIO 157 interrupt occurred
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