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qmk-bot committed Apr 3, 2023
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Expand Up @@ -89,46 +89,38 @@ susceptible to noise, you must choose a debounce method that will also mitigate
* Per-key and per-row algorithms consume more resources (in terms of performance,
and ram usage), but fast typists might prefer them over global.

## Debounce algorithms supported by QMK
## Supported Debounce Algorithms

QMK supports multiple debounce algorithms through its debounce API.

### Debounce selection

| DEBOUNCE_TYPE | Description | What else is needed |
| ------------- | --------------------------------------------------- | ----------------------------- |
| Not defined | Use the default algorithm, currently sym_defer_g | Nothing |
| custom | Use your own debounce code | ```SRC += debounce.c``` add your own debounce.c and implement necessary functions |
| Anything Else | Use another algorithm from quantum/debounce/* | Nothing |

**Regarding split keyboards**:
The debounce code is compatible with split keyboards.

### Selecting an included debouncing method
Keyboards may select one of the already implemented debounce methods, by adding to ```rules.mk``` the following line:
Keyboards may select one of the core debounce methods by adding the following line into ```rules.mk```:
```
DEBOUNCE_TYPE = <name of algorithm>
```
Where name of algorithm is one of:
* ```sym_defer_g``` - debouncing per keyboard. On any state change, a global timer is set. When ```DEBOUNCE``` milliseconds of no changes has occurred, all input changes are pushed.
* This is the current default algorithm. This is the highest performance algorithm with lowest memory usage, and it's also noise-resistant.
* ```sym_eager_pr``` - debouncing per row. On any state change, response is immediate, followed by locking the row ```DEBOUNCE``` milliseconds of no further input for that row.
For use in keyboards where refreshing ```NUM_KEYS``` 8-bit counters is computationally expensive / low scan rate, and fingers usually only hit one row at a time. This could be
appropriate for the ErgoDox models; the matrix is rotated 90°, and hence its "rows" are really columns, and each finger only hits a single "row" at a time in normal use.
* ```sym_eager_pk``` - debouncing per key. On any state change, response is immediate, followed by ```DEBOUNCE``` milliseconds of no further input for that key
* ```sym_defer_pr``` - debouncing per row. On any state change, a per-row timer is set. When ```DEBOUNCE``` milliseconds of no changes have occurred on that row, the entire row is pushed. Can improve responsiveness over `sym_defer_g` while being less susceptible than per-key debouncers to noise.
* ```sym_defer_pk``` - debouncing per key. On any state change, a per-key timer is set. When ```DEBOUNCE``` milliseconds of no changes have occurred on that key, the key status change is pushed.
* ```asym_eager_defer_pk``` - debouncing per key. On a key-down state change, response is immediate, followed by ```DEBOUNCE``` milliseconds of no further input for that key. On a key-up state change, a per-key timer is set. When ```DEBOUNCE``` milliseconds of no changes have occurred on that key, the key-up status change is pushed.

### A couple algorithms that could be implemented in the future:
* ```sym_defer_pr```
* ```sym_eager_g```

### Use your own debouncing code
You have the option to implement you own debouncing algorithm. To do this:
Name of algorithm is one of:

| Algorithm | Description |
| ------------------------- | ----------- |
| ```sym_defer_g``` | Debouncing per keyboard. On any state change, a global timer is set. When ```DEBOUNCE``` milliseconds of no changes has occurred, all input changes are pushed. This is the highest performance algorithm with lowest memory usage and is noise-resistant. |
| ```sym_defer_pr``` | Debouncing per row. On any state change, a per-row timer is set. When ```DEBOUNCE``` milliseconds of no changes have occurred on that row, the entire row is pushed. This can improve responsiveness over `sym_defer_g` while being less susceptible to noise than per-key algorithm. |
| ```sym_defer_pk``` | Debouncing per key. On any state change, a per-key timer is set. When ```DEBOUNCE``` milliseconds of no changes have occurred on that key, the key status change is pushed. |
| ```sym_eager_pr``` | Debouncing per row. On any state change, response is immediate, followed by ```DEBOUNCE``` milliseconds of no further input for that row. |
| ```sym_eager_pk``` | Debouncing per key. On any state change, response is immediate, followed by ```DEBOUNCE``` milliseconds of no further input for that key. |
| ```asym_eager_defer_pk``` | Debouncing per key. On a key-down state change, response is immediate, followed by ```DEBOUNCE``` milliseconds of no further input for that key. On a key-up state change, a per-key timer is set. When ```DEBOUNCE``` milliseconds of no changes have occurred on that key, the key-up status change is pushed. |

?> ```sym_defer_g``` is the default if ```DEBOUNCE_TYPE``` is undefined

?> ```sym_eager_pr``` is suitable for use in keyboards where refreshing ```NUM_KEYS``` 8-bit counters is computationally expensive or has low scan rate while fingers usually hit one row at a time. This could be appropriate for the ErgoDox models where the matrix is rotated 90°. Hence its "rows" are really columns and each finger only hits a single "row" at a time with normal usage.

### Implementing your own debouncing code

You have the option to implement you own debouncing algorithm with the following steps:

* Set ```DEBOUNCE_TYPE = custom``` in ```rules.mk```.
* Add ```SRC += debounce.c``` in ```rules.mk```
* Add your own ```debounce.c```. Look at current implementations in ```quantum/debounce``` for examples.
* Implement your own ```debounce.c```. See ```quantum/debounce``` for examples.
* Debouncing occurs after every raw matrix scan.
* Use num_rows rather than MATRIX_ROWS, so that split keyboards are supported correctly.
* If the algorithm might be applicable to other keyboards, please consider adding it to ```quantum/debounce```
* Use num_rows instead of MATRIX_ROWS to support split keyboards correctly.
* If your custom algorithm is applicable to other keyboards, please consider making a pull request.

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