说明:
yx0--pioA0 yx1--pioA2 yx2--pioA4 yx3--pioA10 yx4--pioA14 yx5--pioA16 yx6--pioA12 yx7--pioA20
使用ｃａｔ方式捕获电平，如果是字符'1',代表输入节点没有闭合，如果是字符'０',代表外部输入节点闭合，
1 配置gpio
root@sama5d3-linux:~ echo 16 > /sys/class/gpio/export
root@sama5d3-linux:~ echo 12 > /sys/class/gpio/export
root@sama5d3-linux:~ echo 10 > /sys/class/gpio/export
root@sama5d3-linux:~ echo 14 > /sys/class/gpio/export
root@sama5d3-linux:~ echo 4 > /sys/class/gpio/export
root@sama5d3-linux:~ echo 2 > /sys/class/gpio/export
root@sama5d3-linux:~ echo 0 > /sys/class/gpio/export
2 配置gpio的方向－－输入
root@sama5d3-linux: echo in > /sys/class/gpio/pioA20/direction
root@sama5d3-linux: echo in > /sys/class/gpio/pioA16/direction
root@sama5d3-linux: echo in > /sys/class/gpio/pioA12/direction
root@sama5d3-linux: echo in > /sys/class/gpio/pioA10/direction
root@sama5d3-linux: echo in > /sys/class/gpio/pioA14/direction
root@sama5d3-linux: echo in > /sys/class/gpio/pioA4/direction
root@sama5d3-linux: echo in > /sys/class/gpio/pioA2/direction
root@sama5d3-linux: echo in > /sys/class/gpio/pioA0/direction
3 捕获电平:
root@sama5d3-linux: cat /sys/class/gpio/pioA20/value //如果返回字符'1',代表输入节点没有闭合，如果是字符'０',代表外部输入节点闭合
root@sama5d3-linux: cat /sys/class/gpio/pioA16/value
root@sama5d3-linux: cat /sys/class/gpio/pioA12/value
root@sama5d3-linux: cat /sys/class/gpio/pioA10/value
root@sama5d3-linux: cat /sys/class/gpio/pioA4/value
root@sama5d3-linux: cat /sys/class/gpio/pioA2/value
root@sama5d3-linux: cat /sys/class/gpio/pioA0/value