利用i2c来控制gpio口
1、编译驱动或者安装驱动
# opkg update
# opkg install kmod-i2c-gpio-custom kmod-i2c-core
# 加载驱动
# insmod i2c-dev
# insmod i2c-gpio-custom bus0=,,
# dmesg | grep gpio
Mar :: openwrt kern.info kernel: [ 52.910000] Custom GPIO-based I2C driver version 0.1.
Mar :: openwrt kern.info kernel: [ 52.910000] i2c-gpio i2c-gpio.: using pins (SDA) and (SCL)
2、找到i2c文件
驱动安装完成，成功加载驱动之后，查看是否存在i2c文件，
文件路径为：
/sys/class/i2c-dev/i2c-