Revision as of 15:29, 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 simple and reliable.

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 used path, 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/Makefile 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@localhost:~/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)

Execute app

Go to:$/svn.hylands.org/linux/gpio/app, gpio will be found here.

To make sure that libgpio.so can be founded as a dependency of gpio program use the following command:

 ldd gpio 

See if libgpio.so is found it. If you execute program in bash without linking library dependencies, bash give you a error message.

Testing driver

Under construction

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