Revision as of 08:15, 14 February 2020

Introduction

GPIO, 全称 General-Purpose Input/Output（通用输入输出），是一种软件运行期间能够动态配置和控制的通用引脚。

RK3399有5组GPIO bank：GPIO0~GPIO4，每组又以 A0~A7, B0~B7, C0~C7, D0~D7 作为编号区分（不是所有 bank 都有全部编号，例如 GPIO4 就只有 C0~C7, D0~D2)。

所有的GPIO在上电后的初始状态都是输入模式，可以通过软件设为上拉或下拉，也可以设置为中断脚，驱动强度都是可编程的。

每个 GPIO 口除了通用输入输出功能外，还可能有其它复用功能，

例如 GPIO2_A2，可以利用成以下功能：

• GPIO2_A2
• CIF_D2

Configuration

The RK3399 bank/bit notation for GPIOs must be formed as "GPIO<GPIO_bank>_<gpio_bit>" 

The numeric value of GPIO is calculated as follows:

32 x (gpio_bank) + gpio_bit

gpio_bit : A0～A7 0-7 B0～B7 8-15 C0～C7 16-23 D0～D7 24-31

E.g. GPIO2_A4 becomes 68

RSB-4710

Test

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

Export GPIO0

# echo 219 > /sys/class/gpio/export

Set GPIO direction to in/out

# echo "out" > /sys/class/gpio/gpio219/direction

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

#  echo 1 > /sys/class/gpio/gpio219/value

Used as IRQ signal

Note:You have to configure GPIO to input

#  echo "rising" > /sys/class/gpio/gpio219/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 219 > /sys/class/gpio/unexport

Test

GPIO 219 and GPIO 220 are taken as an example:

• Connect GPIO 219 and GPIO 220
• Export GPIO 219 and GPIO 220

# echo 219 > /sys/class/gpio/export
# echo 220 > /sys/class/gpio/export

• Set GPIO 219 to output

# echo "out" > /sys/class/gpio/gpio219/direction

• Set GPIO 220 to input

# echo "in" > /sys/class/gpio/gpio220/direction

• Change GPIO 219 to 1 and read GPIO 220 value

# echo 1 > /sys/class/gpio/gpio219/value
# cat /sys/class/gpio/gpio220/value 1

• Change GPIO 219 to 0 and read GPIO 220 value

# echo 0 > /sys/class/gpio/gpio219/value
# cat /sys/class/gpio/gpio220/value 0