AVR is severely resource-constrained, and as QMK continues to grow, it is approaching a point where support for AVR may need to be moved to legacy status as newer development is unable to fit into those constraints.
This will cause the final step to take longer, but should get you a smaller compiled size. This also disables Action Functions, and Action Macros, both of which are deprecated.
This will get you the most savings, in most situations.
These features are enabled by default, but may not be needed. Double check to make sure, though.
Largest in size is "magic" -- the QMK magic keycodes -- which control things like NKRO toggling, GUI and ALT/CTRL swapping, etc. Disabling it will disable those functions.
If you use `sprintf` or `snprintf` functions you can save around ~400 Bytes by enabling this option.
```make
AVR_USE_MINIMAL_PRINTF = yes
```
This will include smaller implementations from AVRs libc into your Firmware. They are [not fully featured](https://www.nongnu.org/avr-libc/user-manual/group__avr__stdio.html#gaa3b98c0d17b35642c0f3e4649092b9f1), for instance zero padding and field width specifiers are not supported. So if you use `sprintf` or `snprintf` like this:
If you've done all of that, and you don't want to disable features like RGB, Audio, OLEDs, etc, there are some additional options that you can add to your config.h that can help.
Starting with Lock Key support. If you have a Cherry MX Lock switch (lucky you!), you don't want to do this. But chances are, you don't. In that case, add this to your `config.h`:
If you're using the Audio feature, by default that includes the music mode feature. This tranlates matrix positions into notes. It's neat for sure, but most likely, you're not using it. You can disable it by adding this to your `config.h`:
There are two `__attribute__ ((weak))` placeholder functions available to customize magic keycodes. If you are not using that feature to swap keycodes, such as backslash with backspace, add the following to your `keymap.c` or user space code:
```c
uint16_t keycode_config(uint16_t keycode) {
return keycode;
}
```
Likewise, if you are not using magic keycodes to swap modifiers, such as Control with GUI, add the following to your `keymap.c` or user space code:
```c
uint8_t mod_config(uint8_t mod) {
return mod;
}
```
Both of them will overwrite the placeholder functions with a simple return statement to reduce firmware size.
One place you can save a bunch of space here is by not using `sprintf` or `snprintf`. This function call takes up ~1.5kB of firmware space, and can be rewritten. For instance, WPM uses this a lot.
If you're using RGB on your board, both RGB Light (Underglow) and RGB Matrix (per key RGB) now require defines to enable different animations -- some keyboards enable a lot of animations by default, so you can generally gain back some space by disabling specific animations if you don't use them. For RGB Light you can disable these in your keymap's `config.h`:
For RGB Matrix, these need to be explicitly enabled as well. To disable any that were enabled by the keyboard, add one or more of these to your keymap's `config.h`:
If you've done all of this, and your firmware is still too large, then it's time. It's time to consider making the switch to ARM. Unfortunately, right now is the worst possible time for that, due to the silicon shortage, and supply chain issues. Getting an ARM chip is difficult, at best, and significantly overpriced, at worst.
