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qmk_firmware/docs/internals_gpio_control.md
Drashna Jaelre 403c139b34 [Docs] Add AVR and ARM examples to GPIO Commands (#6942) 
* [Docs] Add AVR and ARM examples to GPIO Commands

Add examples for reference for people not as well versed in microcontroller coding, such as myself.

* Apply suggestions from code review

Co-Authored-By: fauxpark <fauxpark@gmail.com>
Co-Authored-By: noroadsleft <18669334+noroadsleft@users.noreply.github.com>
2019-10-07 19:08:14 -07:00

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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.

Functions

The following functions can provide basic control of GPIOs and are found in quantum/quantum.h.

Function Description Old AVR Examples Old ChibiOS/ARM Examples
setPinInput(pin) Set pin as input with high impedance (High-Z) DDRB &= ~(1<<2) palSetLineMode(pin, PAL_MODE_INPUT)
setPinInputHigh(pin) Set pin as input with builtin pull-up resistor DDRB &= ~(1<<2); PORTB |= (1<<2) palSetLineMode(pin, PAL_MODE_INPUT_PULLUP)
setPinInputLow(pin) Set pin as input with builtin pull-down resistor N/A (Not supported on AVR) palSetLineMode(pin, PAL_MODE_INPUT_PULLDOWN)
setPinOutput(pin) Set pin as output DDRB |= (1<<2) palSetLineMode(pin, PAL_MODE_OUTPUT_PUSHPULL)
writePinHigh(pin) Set pin level as high, assuming it is an output PORTB |= (1<<2) palSetLine(pin)
writePinLow(pin) Set pin level as low, assuming it is an output PORTB &= ~(1<<2) palClearLine(pin)
writePin(pin, level) Set pin level, assuming it is an output (level) ? PORTB |= (1<<2) : PORTB &= ~(1<<2) (level) ? palSetLine(pin) : palClearLine(pin)
readPin(pin) Returns the level of the pin _SFR_IO8(pin >> 4) & _BV(pin & 0xF) palReadLine(pin)

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 and include any needed libraries. For AVR, the standard avr/io.h library is used; for STM32, the ChibiOS PAL library is used.