qmk_firmware/docs/internals_gpio_control.md
James Young c66df16644
2020 November 28 Breaking Changes Update (#11053)
* Branch point for 2020 November 28 Breaking Change                                                

* Remove matrix_col_t to allow MATRIX_ROWS > 32 (#10183)                                           

* Add support for soft serial to ATmega32U2 (#10204)                                               

* Change MIDI velocity implementation to allow direct control of velocity value (#9940)            

* Add ability to build a subset of all keyboards based on platform.                                

* Actually use eeprom_driver_init().                                                               

* Make bootloader_jump weak for ChibiOS. (#10417)                                                  

* Joystick 16-bit support (#10439)                                                                 

* Per-encoder resolutions (#10259)                                                                 

* Share button state from mousekey to pointing_device (#10179)                                     

* Add hotfix for chibios keyboards not wake (#10088)                                               

* Add advanced/efficient RGB Matrix Indicators (#8564)                                             

* Naming change.                                                                                   

* Support for STM32 GPIOF,G,H,I,J,K (#10206)                                                       

* Add milc as a dependency and remove the installed milc (#10563)                                  

* ChibiOS upgrade: early init conversions (#10214)                                                 

* ChibiOS upgrade: configuration file migrator (#9952)                                             

* Haptic and solenoid cleanup (#9700)                                                              

* XD75 cleanup (#10524)                                                                            

* OLED display update interval support (#10388)                                                    

* Add definition based on currently-selected serial driver. (#10716)                               

* New feature: Retro Tapping per key (#10622)                                                      

* Allow for modification of output RGB values when using rgblight/rgb_matrix. (#10638)             

* Add housekeeping task callbacks so that keyboards/keymaps are capable of executing code for each main loop iteration. (#10530)

* Rescale both ChibiOS and AVR backlighting.                                                       

* Reduce Helix keyboard build variation (#8669)                                                    

* Minor change to behavior allowing display updates to continue between task ticks (#10750)        

* Some GPIO manipulations in matrix.c change to atomic. (#10491)                                   

* qmk cformat (#10767)                                                                             

* [Keyboard] Update the Speedo firmware for v3.0 (#10657)                                          

* Maartenwut/Maarten namechange to evyd13/Evy (#10274)                                             

* [quantum] combine repeated lines of code (#10837)                                                

* Add step sequencer feature (#9703)                                                               

* aeboards/ext65 refactor (#10820)                                                                 

* Refactor xelus/dawn60 for Rev2 later (#10584)                                                    

* add DEBUG_MATRIX_SCAN_RATE_ENABLE to common_features.mk (#10824)                                 

* [Core] Added `add_oneshot_mods` & `del_oneshot_mods` (#10549)                                    

* update chibios os usb for the otg driver (#8893)                                                 

* Remove HD44780 References, Part 4 (#10735)                                                       

* [Keyboard] Add Valor FRL TKL (+refactor) (#10512)                                                

* Fix cursor position bug in oled_write_raw functions (#10800)                                     

* Fixup version.h writing when using SKIP_VERSION=yes (#10972)                                     

* Allow for certain code in the codebase assuming length of string. (#10974)                       

* Add AT90USB support for serial.c (#10706)                                                        

* Auto shift: support repeats and early registration (#9826)                                       

* Rename ledmatrix.h to match .c file (#7949)                                                      

* Split RGB_MATRIX_ENABLE into _ENABLE and _DRIVER (#10231)                                        

* Split LED_MATRIX_ENABLE into _ENABLE and _DRIVER (#10840)                                        

* Merge point for 2020 Nov 28 Breaking Change
2020-11-28 12:02:18 -08:00

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Markdown

# 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)` |
| `togglePin(pin)` | Invert pin level, assuming it is an output | `PORTB ^= (1<<2)` | `palToggleLine(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.
## 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.
```c
void some_function() {
// 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.