I use a J38 GPIOC6 pin, specific operation as follows, please leaders to help analyze why not set up to realize high and low level:
1. Echo 70 & gt;/sys/class/gpio/export
2. The echo out & gt;/sys/class/gpio gpio70/direction
3. The echo 1 & gt;/sys/class/gpio gpio70/value
Using a multimeter test GPIOC6 (J38 pin 13), J38 pin 4 (GND) between the voltage is zero, not 3.3 v