Difference between revisions of "How to use GPIOs"

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'''UNDER MAINTENANCE'''
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== Overview  ==
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{{Message/Obsolete|Link=Only works with kernel 2.6.35.y}}
 
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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] with [[Linux Kernel 2.6.35.y|Kernel 2.6.35.y]], Ubuntu 10.04 with Linaro Toolchain, IGEP v2 RC5 and [http://downloads.igep.es/labs/gpio-driver.tar.bz2 GPIO driver].
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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. For this How-To I used [http://labs.isee.biz/index.php/IGEP_firmware_Yocto IGEP firmware Yocto]
  
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There are more ways to use GPIOs in IGEP v2, but this one is very simple.<br>
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There are more ways to use GPIOs, but this one is very simple.
  
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= Feedback and Contributing  =
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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.<br>
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At any point, if you see a mistake you can contribute to this How-To.
  
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= Compile GPIO driver source code via Host<br>  =
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== Requirements ==
  
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Download [http://downloads.igep.es/labs/gpio-driver.tar.bz2 GPIO driver] and [[Linux Kernel 2.6.35.y|Kernel 2.6.35.y]] source code. Extract files.<br>
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For this How-to, I used:
 +
* IGEPv2 Board
 +
* [http://labs.isee.biz/images/6/69/Gpio_examplebeta1.tar.bz2 GPIO example]
  
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Edit GPIO driver Makefile's:  
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== Configure IGEPv2==
 +
By default, GPIO 156 (J990:20) and GPIO 157 (J990:22) are available, connect J990:20 and J990:22 with a cable.
  
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-In files: $/app/Makefile and $/lib/Makefile, make sure that your CROSS_COMPILE path is correct.
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== Example program ==
  
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-In file: $/modules/Makefile, make sure that your CROSS_COMPILE path is correct and&nbsp;type your Kernel 2.6.35.y path.<br>
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Example program contains some libraries to control GPIOs, libraries can do:
 +
* Export and unexport GPIOs
 +
* Set GPIO direction
 +
* Set GPIO value
 +
* Get GPIO value
 +
* Configure hardware interrupts
  
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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:
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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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<pre>sudo apt-get install ncurses-dev
 
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</pre>
 
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-Go to kernel path and type:
 
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<pre>make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- igep00x0_defconfig
 
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</pre>
 
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Exit Linux Kernel Configuration an return to Bash. Type:
 
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<pre>make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- modules_prepare
 
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</pre>
 
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File $/include/generated/autoconf.h was created
 
  
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Finally compile GPIO driver, go to main Makefile path and compile all source code using make command.  
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=== 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.
  
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Send binaries created from Host to Igep v2. <br>
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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.
 +
<pre>jdoe@ubuntu ~ $ source /opt/poky/1.2/environment-setup-armv7a-vfp-neon-poky-linux-gnueabi </pre>  
  
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= Install binaries via IGEP<br>  =
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* Download [http://labs.isee.biz/images/6/69/Gpio_examplebeta1.tar.bz2 source code]
 +
* Extract source code
 +
* Build source code:
  
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Log with root user to install binaries.  
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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:
 +
<pre>jdoe@ubuntu ~/Desktop $ arm-poky-linux-gnueabi-gcc -o gpio_example gpio_examplebeta1.c</pre>
  
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=== Install module  ===
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* Copy binary file to IGEP Board
  
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Go to:$/modules and insert user-gpio-drv.ko into linux kernel with the following command:  
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== Execute program ==
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<pre>insmod user-gpio-drv.ko
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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>
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<pre>root@igep00x0:~# ./gpio_example 157 </pre>
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Check that user-gpio-drv.ko is currently loaded with the following command:
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Result will be:
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<pre>lsmod</pre>  
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<pre>root@igep00x0:~# ./gpio_example 157
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The result will be similar at that: <br>
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gpio/direction: No such file or directory
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<pre>root@localhost:~/gpio-driver/module# lsmod
 
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Module                  Size  Used by
 
−
user_gpio_drv          1639  0
 
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omap_wdt                3411  0
 
−
spidev                  4198  0
 
−
iommu                  8558  0
 
−
rtc_twl                4411  0
 
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rtc_core              11187  1 rtc_twl
 
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twl4030_keypad          2970  0
 
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</pre>
 
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The module is loaded until system halt.
 
  
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=== Install shared library  ===
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poll() GPIO 157 interrupt occurred
 +
............. </pre>
  
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Go to:$/lib. libgpio.so is here.
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== Generate interrupts ==
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Open a second remote terminal and type:
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If a program is linked with shared libraries, Kernel seek in specific paths when program is executed. Now is necessary link the libgpio.so path to the environment variable LD_LIBRARY_PATH, use the following command:<br>
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<pre>cd /sys/class/gpio/
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<pre>export LD_LIBRARY_PATH=/root/gpio-driver/lib/
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echo 156 > export
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</pre>
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cd gpio156/  
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Check that libgpio.so is linked correctly. Go to:$/gpio-driver/app, gpio program is here. Type next command:
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echo out > direction
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<pre>ldd gpio
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echo 0 > value
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</pre>
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echo 1 > value</pre>
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ldd command, print shared library dependencies. The result will be similar at that:
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== Result ==
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<pre>root@localhost:~/gpio-driver/app# ldd gpio
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At first remote terminal you should read a message similar like this:
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libgpio.so =&gt; /root/gpio-driver/lib/libgpio.so (0x40197000)
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<pre>poll() GPIO 157 interrupt occurred </pre>
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libc.so.6 =&gt; /lib/libc.so.6 (0x401a0000)
 
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/lib/ld-linux.so.3 (0x4008a000)
 
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</pre>
 
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The shared library is linked until system halt. Now you can execute gpio example program.
 
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= Testing driver  =
 
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To make sure than driver works well, make the next test. I used GPIO_136(sdmmc2_dat4) and GPIO_137(sdmmc2_dat5) because IGEP v2 RC5(without WIFI) don't use them by default: <br>
 
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'''NOTE:''' For more information visit this [[Mux configuration|page]] (under construction). <br>  
 
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=== Configure Mux  ===
 
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Go to:/sys/kernel/debug/omap_mux, and change this mux configuration:
 
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<pre>echo 0x104&gt;sdmmc2_dat4
 
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echo 0x104&gt;sdmmc2_dat5
 
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</pre>  
 
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Use cat command to check it:<br>
 
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<pre>cat sdmmc2_dat4
 
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cat sdmmc2_dat5
 
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</pre>
 
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The result will be similar at that:
 
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<pre>root@localhost:/sys/kernel/debug/omap_mux# cat sdmmc2_dat4
 
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name: sdmmc2_dat4.gpio_136 (0x48002164/0x134 = 0x0104), b ae4, t NA
 
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mode: OMAP_PIN_INPUT | OMAP_MUX_MODE4
 
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signals: sdmmc2_dat4 | sdmmc2_dir_dat0 | NA | sdmmc3_dat0 | gpio_136 | NA | NA | safe_mode
 
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</pre>  
 
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and
 
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<pre>root@localhost:/sys/kernel/debug/omap_mux# cat sdmmc2_dat5
 
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name: sdmmc2_dat5.gpio_137 (0x48002166/0x136 = 0x0104), b ah3, t NA
 
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mode: OMAP_PIN_INPUT | OMAP_MUX_MODE4
 
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signals: sdmmc2_dat5 | sdmmc2_dir_dat1 | cam_global_reset | sdmmc3_dat1 | gpio_137 | hsusb3_tll_stp | mm3_rxdp | safe_mode
 
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</pre>  
 
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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>
 
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=== Read/Write test  ===
 
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Link GPIO_136 and GPIO_137 with a wire, these pins are located in J990 connector with numbers 7 and 9. I use the next connector to join them:<br>
 
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{| cellspacing="1" cellpadding="1" border="1" align="center" width="200"
 
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|-
 
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| [[Image:Connector used readwrite test.JPG|center|350x230px]]
 
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|
 
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[[Image:All connected readwrite test.JPG|center|350x230px]]
 
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|}
 
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<br>
 
−
 
 
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Now type next code:  
 
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<pre>root@localhost:~/gpio-driver/app# ./gpio input 136
 
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root@localhost:~/gpio-driver/app# ./gpio output 137 0
 
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root@localhost:~/gpio-driver/app# ./gpio get 136   
 
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0
 
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root@localhost:~/gpio-driver/app# ./gpio output 137 1
 
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root@localhost:~/gpio-driver/app# ./gpio get 136   
 
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1
 
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root@localhost:~/gpio-driver/app#
 
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</pre>
 
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The results (CMOS Voltages: 0V-1V8):
 
−
 
 
−
{| cellspacing="1" cellpadding="1" border="1" align="center" width="200"
 
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|-
 
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| [[Image:GPIO value0 readwrite test.JPG|center|350x230px]]
 
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|
 
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[[Image:GPIO value1 readwrite test.JPG|center|350x230px]]
 
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|}
 
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<br> 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.
 
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<br> Other examples:[[What can I do with IGEP0020#How_to_handle_the_gpio-LED.27s]]
 
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[[Category:GPIO]]
 

Revision as of 18:54, 14 September 2012

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. For this How-To I used IGEP firmware Yocto

There are more ways to use GPIOs, but this one is very simple.

Feedback and Contributing

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

Requirements

For this How-to, I used:

Configure IGEPv2

By default, GPIO 156 (J990:20) and GPIO 157 (J990:22) are available, connect J990:20 and J990:22 with a cable.

Example program

Example program contains some libraries to control GPIOs, libraries 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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