Kernel Interfaces
root@platform:~# dmesg | grep -i gpio
root@platform:~# ls /sys/class/gpio/
root@platform:~# ls /sys/class/gpio/gpio13
root@platform:~# echo 13 > /sys/class/gpio/export
root@platform:~# ls /sys/class/gpio/gpio13
active_low direction drive edge power subsystem uevent value
root@platform:~# echo in > /sys/class/gpio/gpio13/direction
root@platform:~# echo out > /sys/class/gpio/gpio13/direction
root@platform:~# echo 1 > /sys/class/gpio/gpio13/value
root@platform:~# cat /sys/class/gpio/gpio13/value
root@platform:~# echo 0 > /sys/class/gpio/gpio13/value
root@platform:~# cat /sys/class/gpio/gpio13/value
I2C (Inter-IC)
root@platform:~# dmesg | grep -i i2c
root@platform:~# ls /sys/class/i2c-dev/
i2c-0
root@platform:~# i2cdetect -y -r <Bus>
root@platform:~# i2cdump -f -y <Bus> <0xAddress>