Revision as of 16:15, 9 January 2012

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, Ubuntu 10.04 with Linaro Toolchain, IGEP v2 RC5 and GPIO driver wrote by Dave Hylands. 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 source code from author website using the next command:

wget -r -np  http://svn.hylands.org/linux/gpio/

Due the source Makefiles are implemented for Gumstix SDK, it is necessary change some constants for compile with our Host. These constants are:

In files:

$/svn.hylands.org/linux/gpio/app/Makefile

$/svn.hylands.org/linux/gpio/lib/Makefile

Search lines:

OVEROTOP	?= /home/gumstix/overo-oe
CROSS_COMPILE	?= $(OVEROTOP)/tmp/sysroots/x86_64-linux/usr/armv7a/bin/arm-angstrom-linux-gnueabi-

Replaced by your cross compiler path, for example:

OVEROTOP	?= /
CROSS_COMPILE	?= $(OVEROTOP)/usr/bin/arm-linux-gnueabi-

In file:

$/svn.hylands.org/linux/gpio/modules/Makefile

Search lines:

OVEROTOP	?= /home/gumstix/overo-oe
#CROSS_COMPILE	?= $(OVEROTOP)/tmp/cross/armv7a/bin/arm-angstrom-linux-gnueabi-
CROSS_COMPILE	?= $(OVEROTOP)/tmp/sysroots/x86_64-linux/usr/armv7a/bin/arm-angstrom-linux-gnueabi-
KERNEL_PATH     ?= ../../../../../gumstix/overo-oe/tmp/sysroots/overo-angstrom-linux-gnueabi/kernel
ARCH		?= arm

Replaced by your cross compiler path and your kernel source path used, for example:

OVEROTOP	?= /
#CROSS_COMPILE	?= $(OVEROTOP)/tmp/cross/armv7a/bin/arm-angstrom-linux-gnueabi-
CROSS_COMPILE	?= $(OVEROTOP)//usr/bin/arm-linux-gnueabi-
KERNEL_PATH     ?= ../../../../../<your kernel source path used>
ARCH		?= arm

Go to: $/svn.hylands.org/linux/gpio/ and compile all source code downloaded 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:$/svn.hylands.org/linux/gpio/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 than this:

root@localhost:~/svn.hylands.org/linux/gpio/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.

Install dynamic library

Go to:$/svn.hylands.org/linux/gpio/lib/. libgpio.so will be found here.

If a program is link with dinamic libraries, Linux kernel find this ones in a specific paths when program is executed. Now is necessary link the libgpio.so path to the envireonment variable LD_LIBRARY_PATH, use the following commnad:

export LD_LIBRARY_PATH=/root/svn.hylands.org/linux/gpio/lib/

Check that libgpio.so is linked correctly. Go to:$/svn.hylands.org/linux/gpio/app, gpio program will be found here. Type next command:

ldd gpio 

ldd command list program dependencies and show its paths. The result will be similar than this:

root@lSee if libgpio.so is found it. If you execute program in bash without linking library dependencies, bash give you a error message. ocalhost:~/svn.hylands.org/linux/gpio/app# ldd gpio
	libgpio.so => /root/svn.hylands.org/linux/gpio/lib/libgpio.so (0x40197000)
	libc.so.6 => /lib/libc.so.6 (0x401a0000)
	/lib/ld-linux.so.3 (0x4008a000)

Now you can execute example program gpio.

Testing driver

To make sure than driver works well, make the next test with GPIO_136 and GPIO_137:

NOTE: Make sure that MMC2_DAT4 and MMC2_DAT5 are not used, for more information visit this page. With IGEP v2 RC5 (version without WIFI) this pins are not used by default.

Configure Mux

Go to:/sys/kernel/debug/omap_mux, and change the this mux configuration:

echo 0x104>sdmmc2_dat4
echo 0x104>sdmmc2_dat5

Use cat to check it:

cat sdmmc2_dat4
cat sdmmc2_dat5

The result will be similar than this:

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 and Output pin and OMAP_PIN_OUTPUT=Output pin.

Read/Write test

Link GPIO_136 and GPIO_137 with a wire, these pins are located in J990 connector with numbers 7 and 9. Type next text:

root@localhost:~/svn.hylands.org/linux/gpio/app# ./gpio input 136
root@localhost:~/svn.hylands.org/linux/gpio/app# ./gpio output 137 0
root@localhost:~/svn.hylands.org/linux/gpio/app# ./gpio get 136     
0
root@localhost:~/svn.hylands.org/linux/gpio/app# ./gpio output 137 1
root@localhost:~/svn.hylands.org/linux/gpio/app# ./gpio get 136     
1
root@localhost:~/svn.hylands.org/linux/gpio/app# 

The text above show that driver work properly, GPIO_136 is configure like input and GPIO_137 is configure like output with value 0, now read GPIO_136 and the result is 0. To make sure configure GPIO_137 with value 1 and GPIO_136 read 1.
This driver have more options like IRQ, but is not explained here.

Under construction

Other examples:What can I do with IGEP0020#How_to_handle_the_gpio-LED.27s