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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.
## Functions :id=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 :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 and include any needed libraries. For AVR, the standard avr/io.h library is used; for STM32, the ChibiOS [PAL library](http://chibios.sourceforge.net/docs3/hal/group___p_a_l.html) is used.
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