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= How to use GPIOs =
== 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 [http://downloads.igep.es/labs/gpio-driver.tar.bz2 GPIO driver].
There are more ways to use GPIOs in IGEP v2, but this one is very simple.<br>
== Feedback and Contributing ==
At any point, if you see a mistake you can contribute to this How-To.<br>
== Compile GPIO driver source code via Host<br> ==
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>
Edit GPIO driver Makefile's:
-In files: $/app/Makefile and $/lib/Makefile, make sure that your CROSS_COMPILE path is correct.
-In file: $/modules/Makefile, make sure that your CROSS_COMPILE path is correct and type your Kernel 2.6.35.y path.<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:
<pre>sudo apt-get install ncurses-dev
</pre>
-Go to kernel path and type:
<pre>make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- igep00x0_defconfig
</pre>
Exit Linux Kernel Configuration an return to Bash. Type:
<pre>make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- modules_prepare
</pre>
File $/include/generated/autoconf.h was created
Finally compile GPIO driver, go to main Makefile path and compile all source code using make command.
Send binaries created from Host to Igep v2. <br>
== Install binaries via IGEP<br> ==
Log with root user to install binaries.
=== Install module ===
Go to:$/modules and insert user-gpio-drv.ko into linux kernel with the following command:
<pre>insmod user-gpio-drv.ko
</pre>
Check that user-gpio-drv.ko is currently loaded with the following command:
<pre>lsmod</pre>
The result will be similar at that: <br>
<pre>root@localhost:~/gpio-driver/module# lsmod
Module Size Used by
user_gpio_drv 1639 0
omap_wdt 3411 0
spidev 4198 0
iommu 8558 0
rtc_twl 4411 0
rtc_core 11187 1 rtc_twl
twl4030_keypad 2970 0
</pre>
The module is loaded until system halt.
=== Install shared library ===
Go to:$/lib. libgpio.so is here.
If a program is linked with shared libraries, Kernel seek in specific paths when program is executed. Now is necessary link the libgpio.so path to the environment variable LD_LIBRARY_PATH, use the following command:<br>
<pre>export LD_LIBRARY_PATH=/root/gpio-driver/lib/
</pre>
Check that libgpio.so is linked correctly. Go to:$/gpio-driver/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@localhost:~/gpio-driver/app# ldd gpio
libgpio.so => /root/gpio-driver/lib/libgpio.so (0x40197000)
libc.so.6 => /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.
== Testing driver ==
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>
'''NOTE:''' For more information visit this [[Mux configuration|page]] (under construction). <br>
=== Configure Mux ===
Go to:/sys/kernel/debug/omap_mux, and change this mux configuration:
<pre>echo 0x104>sdmmc2_dat4
echo 0x104>sdmmc2_dat5
</pre>
Use cat command to check it:<br>
<pre>cat sdmmc2_dat4
cat sdmmc2_dat5
</pre>
The result will be similar at that:
<pre>root@localhost:/sys/kernel/debug/omap_mux# cat sdmmc2_dat4
name: sdmmc2_dat4.gpio_136 (0x48002164/0x134 = 0x0104), b ae4, t NA
mode: OMAP_PIN_INPUT | OMAP_MUX_MODE4
signals: 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_dat5
name: sdmmc2_dat5.gpio_137 (0x48002166/0x136 = 0x0104), b ah3, t NA
mode: OMAP_PIN_INPUT | OMAP_MUX_MODE4
signals: 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. I use the next connector to join them:<br>
{| cellspacing="1" cellpadding="1" width="200" border="1" align="center"
|-
| [[Image:Connector used readwrite test.JPG|center|350x230px]]
|
[[Image:All connected readwrite test.JPG|center|350x230px]]
|}
<br>
Now type next code:
<pre>root@localhost:~/gpio-driver/app# ./gpio input 136
root@localhost:~/gpio-driver/app# ./gpio output 137 0
root@localhost:~/gpio-driver/app# ./gpio get 136
0
root@localhost:~/gpio-driver/app# ./gpio output 137 1
root@localhost:~/gpio-driver/app# ./gpio get 136
1
root@localhost:~/gpio-driver/app#
</pre>
The results (CMOS Voltages: 0V-1V8):
{| cellspacing="1" cellpadding="1" width="200" border="1" align="center"
|-
| [[Image:GPIO value0 readwrite test.JPG|center|350x230px]]
|
[[Image:GPIO value1 readwrite test.JPG|center|350x230px]]
|}
<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.
<br> Other examples:[[What can I do with IGEP0020#How_to_handle_the_gpio-LED.27s]]
[[Category:GPIO]]
=How to use UARTs=
