LED灯所在的GPIO管脚：GPIO1_A2

GPIOa_bc
d=b-'A'='A'-'A'=0
a=1, d=0, c=2

GPIO号=32a+8d+c
      =32×1+8×0+2
      =34

产生gpio34文件夹：echo 34 > /sys/class/gpio/export

GPIO管脚设置为输入：echo in > /sys/class/gpio/gpio34/direction
读取输入的电平：cat /sys/class/gpio/gpio34/value

GPIO管脚设置为输出：echo out > /sys/class/gpio/gpio34/direction
GPIO输出高电平（灯亮）：echo 1 > /sys/class/gpio/gpio34/value
GPIO输出低电平（灯灭）：echo 0 > /sys/class/gpio/gpio34/value