IoTGateway/BSP/Android/Gettingstarted/How to use GPIO

Configuration/Test

Configuration

The i.MX 6 bank/bit notation for GPIOs must be formed as "GPIO<GPIO_bank>_IO<gpio_bit>" 

The numeric value of GPIO is calculated as follows:

32 x (gpio_bank- 1) + gpio_bit

E.g. GPIO2_IO04 becomes 36

ROM-3421

GPIO Number	GPIO formed	Numeric Representation
GPIO0	GPIO_1	1
GPIO1	GPIO2_IO2	34
GPIO2	GPIO2_IO3	35
GPIO3	GPIO_3	3
GPIO4	GPIO7_IO12	204
GPIO5	GPIO7_IO13	205
GPIO6	GPIO7_IO6	198
GPIO7	GPIO6_IO08	168
GPIO8	GPIO2_IO06	38

ROM7420

GPIO Number	GPIO formed	Numeric Representation
GPIO0	GPIO6_IO11	171
GPIO1	GPIO6_IO14	174
GPIO2	GPIO6_IO15	175
GPIO3	GPIO6_IO16	176
GPIO4	GPIO2_IO25	57
GPIO5	GPIO2_IO23	55
GPIO6	GPIO2_IO24	56
GPIO7	GPIO5_IO02	130

Test

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

Export GPIO 27

# echo 27 > /sys/class/gpio/export

Set GPIO direction to in/out

# echo "out" > /sys/class/gpio/gpio27/direction

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

#  echo 1 > /sys/class/gpio/gpio27/value

Used as IRQ signal

Note:You have to configure GPIO to input

#  echo "rising" > /sys/class/gpio/gpio27/edge

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

Unexport GPIO 27

# echo 27 > /sys/class/gpio/unexport

Test

GPIO 27 and GPIO 29 are taken as an example:

• Connect GPIO 27 and GPIO 29
• Export GPIO 27 and GPIO 29

# echo 27 /sys/class/gpio/export
# echo 29 /sys/class/gpio/export

• Set GPIO 27 to output

# echo "out" > /sys/class/gpio/gpio27/direction

• Set GPIO 29 to input

# echo "in" > /sys/class/gpio/gpio29/direction

• Change GPIO 27 to 1 and read GPIO 29 value

# echo 1 > /sys/class/gpio/gpio27/value
# cat /sys/class/gpio/gpio29/value
1

• Change GPIO 27 to 0 and read GPIO 29 value

# echo 0 > /sys/class/gpio/gpio27/value
# cat /sys/class/gpio/gpio29/value
0