How to use GPIO

Configuration/Test

Configuration

The general-purpose interface combines eight general-purpose input/output (GPIO) banks.

Each GPIO module provides 32 dedicated general-purpose pins with input and output capabilities; thus, the general-purpose interface supports up to 256 (8 × 32) pins.

The numeric value of GPIO is calculated as follows:

32 x (gpio_bank - 1) + gpio_bit

ROM-7510

GPIO Number	Linux OS(/sys/class/gpio/)	Default direction
GPIO0	gpio97	in
GPIO1	gpio218	in
GPIO2	gpio98	in
GPIO3	gpio219	in
GPIO4	gpio100	in
GPIO5	gpio68	in
GPIO6	gpio101	in
GPIO7	gpio69	in

Test

Export GPIO then you can use control GPIO from userr space through sysfs

Export GPIO0

# echo 97 > /sys/class/gpio/export

Set GPIO direction to in/out

# echo "out" > /sys/class/gpio/gpio97/direction

Set GPIO value 0/1 if GPIO pin define is output

#  echo 1 > /sys/class/gpio/gpio97/value

Used as IRQ signal

Note:You have to configure GPIO to input

#  echo "rising" > /sys/class/gpio/gpio97/edge

• rising: Trigger on rising edge
• falling: Trigger on falling edge
• both: Trigger on both edges
• none: Disable interrupt on both edges

Unexport GPIO0

# echo 97 > /sys/class/gpio/unexport

Test

GPIO 97 and GPIO 218 are taken as an example:

• Connect GPIO 97 and GPIO 218
• Export GPIO 97 and GPIO 218

# echo 97 > /sys/class/gpio/export
# echo 218 > /sys/class/gpio/export

• Set GPIO 97 to output

# echo "out" > /sys/class/gpio/gpio97/direction

• Set GPIO 218 to input

# echo "in" > /sys/class/gpio/gpio218/direction

• Change GPIO 97 to 1 and read GPIO 218 value

# echo 1 > /sys/class/gpio/gpio97/value
# cat /sys/class/gpio/gpio218/value
1

• Change GPIO 97 to 0 and read GPIO 218 value

# echo 0 > /sys/class/gpio/gpio97/value
# cat /sys/class/gpio/gpio218/value
0