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qmk_firmware/gpio_control.md

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GPIO Control :id=gpio-control

QMK has a GPIO control abstraction layer which is microcontroller agnostic. This is done to allow easy access to pin control across different platforms.

Macros :id=macros

The following macros provide basic control of GPIOs and are found in platforms/<platform>/gpio.h.

Macro Description
gpio_set_pin_input(pin) Set pin as input with high impedance (High-Z)
gpio_set_pin_input_high(pin) Set pin as input with builtin pull-up resistor
gpio_set_pin_input_low(pin) Set pin as input with builtin pull-down resistor (unavailable on AVR)
gpio_set_pin_output(pin) Set pin as output (alias of gpio_set_pin_output_push_pull)
gpio_set_pin_output_push_pull(pin) Set pin as output, push/pull mode
gpio_set_pin_output_open_drain(pin) Set pin as output, open-drain mode (unavailable on AVR and ATSAM)
gpio_write_pin_high(pin) Set pin level as high, assuming it is an output
gpio_write_pin_low(pin) Set pin level as low, assuming it is an output
gpio_write_pin(pin, level) Set pin level, assuming it is an output
gpio_read_pin(pin) Returns the level of the pin
gpio_toggle_pin(pin) Invert pin level, assuming it is an output

Advanced Settings :id=advanced-settings

Each microcontroller can have multiple advanced settings regarding its GPIO. This abstraction layer does not limit the use of architecture-specific functions. Advanced users should consult the datasheet of their desired device. For AVR, the standard avr/io.h library is used; for STM32, the ChibiOS PAL library is used.

Atomic Operation :id=atomic-operation

The above functions are not always guaranteed to work atomically. Therefore, if you want to prevent interruptions in the middle of operations when using multiple combinations of the above functions, use the following ATOMIC_BLOCK_FORCEON macro.

eg.

void some_function(void) {
     // some process
     ATOMIC_BLOCK_FORCEON {
        // Atomic Processing
     }
     // some process
}

ATOMIC_BLOCK_FORCEON forces interrupts to be disabled before the block is executed, without regard to whether they are enabled or disabled. Then, after the block is executed, the interrupt is enabled.

Note that ATOMIC_BLOCK_FORCEON can therefore be used if you know that interrupts are enabled before the execution of the block, or if you know that it is OK to enable interrupts at the completion of the block.