Linux下控制GPIO的方法有N种，详细请参考《RPi GPIO Code Samples》，文中用十多种语言演示了如何控制GPIO，非常全面详尽。因此，这里不再多做赘述，仅把调试过程中整理的脚本贴上并做简单的分析。特别说明，Linux必须有root权限！！！否则会出现/system/bin/sh: can't create /sys/class/gpio/export: Permission denied等错误。
@echo off
echo adb root
adb root >%temp%\_tmp
@findstr "already" %temp%\_tmp
@if NOT errorlevel goto config
timeout /T :config
@echo on
adb shell chmod /sys/class/gpio/export
adb shell chmod /sys/class/gpio/unexport adb shell echo ">" /sys/class/gpio/export
adb shell echo ">" /sys/class/gpio/export adb shell chmod /sys/class/gpio/gpio62/direction
adb shell chmod /sys/class/gpio/gpio63/direction
adb shell chmod /sys/class/gpio/gpio62/value
adb shell chmod /sys/class/gpio/gpio63/value adb shell echo out ">" /sys/class/gpio/gpio62/direction
adb shell echo out ">" /sys/class/gpio/gpio63/direction
adb shell echo ">" /sys/class/gpio/gpio62/value
adb shell echo ">" /sys/class/gpio/gpio63/value @echo off
:top
adb shell echo ">" /sys/class/gpio/gpio62/value
adb shell echo ">" /sys/class/gpio/gpio63/value
rem @timeout /T
for /l %%i in (,,) do echo %%i>nul
rem ping 0.0.0.1 -n -w >nul
adb shell echo ">" /sys/class/gpio/gpio62/value
adb shell echo ">" /sys/class/gpio/gpio63/value
rem @timeout /T
for /l %%i in (,,) do echo %%i>nul
rem ping 0.0.0.1 -n -w >nul
goto top pause.
该批处理文件运行在PC上，通过adb发送shell命令操作/sys/class/gpio以控制GPIO。
在MSM8996的开发板上测试，运行结果如下图所示。
从图中可以看出，两个GPIO的控制时间间隔相差约40ms，说明GPIO控制延时较为严重。
#!/system/bin/sh
chmod /sys/class/gpio/export
chmod /sys/class/gpio/unexport echo > /sys/class/gpio/export
echo > /sys/class/gpio/export chmod /sys/class/gpio/gpio62/direction
chmod /sys/class/gpio/gpio63/direction
chmod /sys/class/gpio/gpio62/value
chmod /sys/class/gpio/gpio63/value echo out > /sys/class/gpio/gpio62/direction
echo out > /sys/class/gpio/gpio63/direction
echo > /sys/class/gpio/gpio62/value
echo > /sys/class/gpio/gpio63/value while :
do
echo > /sys/class/gpio/gpio62/value
echo > /sys/class/gpio/gpio63/value
usleep
echo > /sys/class/gpio/gpio62/value
echo > /sys/class/gpio/gpio63/value
usleep
done
该脚本运行在MSM8996开发板上，通过操作/sys/class/gpio以控制GPIO，执行结果如下图所示。
从图中可以看出，两个GPIO的控制时间间隔相差约0.6ms，说明GPIO控制延时较小。
Android脚本文件可通过如下命令发送到开发板上，并修改其属性。
pushd %~dp0
adb push .\gpio.sh /data/local/
adb shell chmod 777 /data/local/gpio.sh
参考:
How to use GPIO signals(Linux应用程序控制GPIO) PNG
https://developer.ridgerun.com/wiki/index.php/How_to_use_GPIO_signals
树莓派上使用多种语言(C、Python、shell)控制GPIO
http://elinux.org/RPi_GPIO_Code_Samples
安卓应用程序通过JNI控制GPIO
http://android.serverbox.ch/?p=972
Device Tree Usage
http://elinux.org/Device_Tree_Usage
BeagleBone Black (BBB) Pin Muxes
http://www.valvers.com/embedded-linux/beaglebone-black/step04-gpio
Beaglebone Pin Muxes
http://www.valvers.com/embedded-linux/beaglebone/step04-gpio1
Using Device Trees To Configure PRU IO Pins
http://www.ofitselfso.com/BeagleNotes/UsingDeviceTreesToConfigurePRUIOPins.php
BeagleBone Black GPIOs
http://kilobaser.com/blog/2014-07-15-beaglebone-black-gpios
gpio-header
https://github.com/nomel/beaglebone/tree/master/gpio-header
beaglebone-universal-io