Difference between revisions of "How to use GPIOs"
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<br> Other examples:[[What can I do with IGEP0020#How_to_handle_the_gpio-LED.27s]] | <br> Other examples:[[What can I do with IGEP0020#How_to_handle_the_gpio-LED.27s]] | ||
− | [[Category: | + | [[Category:Peripherals|GPIO]] |
[[Category:Tutorials]] | [[Category:Tutorials]] | ||
[[Category:GPIO]] | [[Category:GPIO]] |
Revision as of 11:43, 20 April 2012
Contents
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 Linaro Headless with Kernel 2.6.35.y, Ubuntu 10.04 with Linaro Toolchain, IGEP v2 RC5 and GPIO driver.
There are more ways to use GPIOs in IGEP v2, but this one is very simple.
Feedback and Contributing
At any point, if you see a mistake you can contribute to this How-To.
Compile GPIO driver source code via Host
Download GPIO driver and Kernel 2.6.35.y source code. Extract files.
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.
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:
sudo apt-get install ncurses-dev
-Go to kernel path and type:
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- igep00x0_defconfig
Exit Linux Kernel Configuration an return to Bash. Type:
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- modules_prepare
File $/include/generated/autoconf.h was created
Finally compile GPIO driver, go to main Makefile path and compile all source code using make command.
Send binaries created from Host to Igep v2.
Install binaries via IGEP
Log with root user to install binaries.
Install module
Go to:$/modules and insert user-gpio-drv.ko into linux kernel with the following command:
insmod user-gpio-drv.ko
Check that user-gpio-drv.ko is currently loaded with the following command:
lsmod
The result will be similar at that:
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
The module is loaded until system halt.
Go to:$/lib. libgpio.so is here.
If a program is linked with shared libraries, Kernel seek in specific paths when program is executed. Now is necessary link the libgpio.so path to the environment variable LD_LIBRARY_PATH, use the following command:
export LD_LIBRARY_PATH=/root/gpio-driver/lib/
Check that libgpio.so is linked correctly. Go to:$/gpio-driver/app, gpio program is here. Type next command:
ldd gpio
ldd command, print shared library dependencies. The result will be similar at that:
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)
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:
NOTE: For more information visit this page (under construction).
Configure Mux
Go to:/sys/kernel/debug/omap_mux, and change this mux configuration:
echo 0x104>sdmmc2_dat4 echo 0x104>sdmmc2_dat5
Use cat command to check it:
cat sdmmc2_dat4 cat sdmmc2_dat5
The result will be similar at that:
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
and
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
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.
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:
Now type next code:
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#
The results (CMOS Voltages: 0V-1V8):
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.
This driver have more options like IRQ, but is not explained here.
Other examples:What can I do with IGEP0020#How_to_handle_the_gpio-LED.27s