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Switch GPIO Function

Some pins carry functions such as I2C, UART, SPI, etc. You need to use the set-device command to enable the configuration before you can use Python or C for embedded programming applications.

The working principle of set-device is based on Linux's device tree overlay feature. We have written information such as "configure pin xx as SPI and enable the corresponding driver" into configuration files (.dtb). This command controls which configuration files (.dtb) the system loads at boot.

Note that some drivers are mutually exclusive. For example, enabling the 3.5-inch display occupies SPI1, so you cannot simultaneously use the spidev1.0 driver. If you configure pins 38/40 of the Walnut Pi 2B as UART4, then these two pins cannot be used for hardware PWM.

For example, pin PI13 can be set as pwm3 or uart4_txd. If you set it as uart4_txd, you cannot use the pwm3 function.

View GPIO Device Status​

Use the following command to view the status of all GPIO devices:

set-device status
  • Status off: The item is not active
  • Status enable: The corresponding pin will be configured and the driver will be enabled.

gpio_config1

Enable GPIO Device​

Use the following command to enable a GPIO device:

sudo set-device enable xx

Example: Enable uart4

sudo set-device enable uart4

After enabling, a restart is required to take effect:

sudo reboot

After running the above commands again, use the set-device status command to see that the uart4 device has been enabled.

gpio_config2

After running the gpio pins command, you can also see that the corresponding pin of the Walnut Pi 2B has been switched to the corresponding operating mode.

gpio_pins_uart4

Disable GPIO Device​

Use the following command to disable a GPIO device:

sudo set-device disable xx

After disabling, a restart is required to take effect:

sudo reboot