【触觉智能 Purple Pi开发板试用】+03.GPIO测试（zmj）
Purple Pi开发板通过J12排针提供了丰富的GPIO接口，包括UART、SPI、I2C、GPIO等（还包括DC5V、DC3.3V、GND）。

本节主要测试Purple Pi开发板的GPIO接口（输出功能）。其中LED添加限流电阻，连接到GPIO-88和GND管脚。

1. GPIO单步测试流程

首先检视GPIO设备，然后申请GPIO设备（此处申请GPIO-88），接着设置GPIO属性（包括输入输出和Value）。

//------GPIO单步测试流程
a.检视GPIO设备
ls -la /sys/class/gpio
b.申请GPIO设备（GPIO-88）
echo 88 > /sys/class/gpio/export
c.此时重新检视GPIO设备，发现多了gpio88的设备
ls -la /sys/class/gpio
d.检视GPIO-88属性（输入输出方向，引脚电平）
cat /sys/class/gpio/gpio88/direction && cat /sys/class/gpio/gpio88/value
e.设置GPIO-88属性：输出out，值为高电平“1”
echo out > /sys/class/gpio/gpio88/direction
echo 1 > /sys/class/gpio/gpio88/value
f.此时LED点亮。

详细Log如下所示：

# ls -la /sys/class/gpio
total 0
drwxr-xr-x    2 root     root             0 Jan  1 00:00 .
drwxr-xr-x   35 root     root             0 Jan  1 00:00 ..
--w-------    1 root     root          4096 Jan  1 00:00 export
lrwxrwxrwx    1 root     root             0 Jan  1 00:00 gpio72 -> ../../devices/gpiochip0/gpio/gpio72
lrwxrwxrwx    1 root     root             0 Jan  1 00:00 gpiochip0 -> ../../devices/gpiochip0/gpio/gpiochip0
--w-------    1 root     root          4096 Jan  1 00:00 unexport
# 
# echo 88 > /sys/class/gpio/export
#
# ls -la /sys/class/gpio
total 0
drwxr-xr-x    2 root     root             0 Jan  1 00:00 .
drwxr-xr-x   35 root     root             0 Jan  1 00:00 ..
--w-------    1 root     root          4096 Jan  1 00:06 export
lrwxrwxrwx    1 root     root             0 Jan  1 00:00 gpio72 -> ../../devices/gpiochip0/gpio/gpio72
lrwxrwxrwx    1 root     root             0 Jan  1 00:06 gpio88 -> ../../devices/gpiochip0/gpio/gpio88
lrwxrwxrwx    1 root     root             0 Jan  1 00:00 gpiochip0 -> ../../devices/gpiochip0/gpio/gpiochip0
--w-------    1 root     root          4096 Jan  1 00:00 unexport
# ls -la /sys/class/gpio/gpio88/
total 0
drwxr-xr-x    3 root     root             0 Jan  1 00:06 .
drwxr-xr-x    5 root     root             0 Jan  1 00:00 ..
-rw-r--r--    1 root     root          4096 Jan  1 00:09 active_low
lrwxrwxrwx    1 root     root             0 Jan  1 00:09 device -> ../../../gpiochip0
-rw-r--r--    1 root     root          4096 Jan  1 00:09 direction
-rw-r--r--    1 root     root          4096 Jan  1 00:09 edge
drwxr-xr-x    2 root     root             0 Jan  1 00:09 power
lrwxrwxrwx    1 root     root             0 Jan  1 00:09 subsystem -> ../../../../class/gpio
-rw-r--r--    1 root     root          4096 Jan  1 00:06 uevent
-rw-r--r--    1 root     root          4096 Jan  1 00:09 value
# cat /sys/class/gpio/gpio88/direction && cat /sys/class/gpio/gpio88/value
in
1
#
# echo out > /sys/class/gpio/gpio88/direction
# echo 1 > /sys/class/gpio/gpio88/value
#
# cat /sys/class/gpio/gpio88/direction && cat /sys/class/gpio/gpio88/value
out
1
#

2. GPIO循环点灯

参考脚本，循环对GPIO-88赋值“1”和“0”，这样控制LED循环亮灭。

//------gpio_led.sh
#!/bin/sh
while true;
do
echo 1 > /sys/class/gpio/gpio88/value
sleep 1
echo 0 > /sys/class/gpio/gpio88/value
sleep 1
done