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qmk_firmware

custom branch of QMK firmware git clone https://anongit.hacktivis.me/git/qmk_firmware.git

squeezing_avr.md (9058B)

    

  1. # Squeezing the most out of AVR
  3. 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.
  5. However, if you need to reduce the compiled size of your firmware to fit the controller's limited flash size, there are a number of options to do so.
  7. ## `rules.mk` Settings
  8. First and foremost is enabling link time optimization. To do so, add this to your rules.mk: 
  9. ```make
  10. LTO_ENABLE = yes
  11. ```
  12. 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.
  13. This will get you the most savings, in most situations.
  15. From there, disabling extraneous systems will help -- e.g.: 
  16. ```make
  17. CONSOLE_ENABLE = no
  18. COMMAND_ENABLE = no
  19. MOUSEKEY_ENABLE = no
  20. EXTRAKEY_ENABLE = no
  21. ```
  22. This disables some of the functionality that you may not need. But note that extrakeys disables stuff like the media keys and system volume control.
  24. If that isn't enough to get your firmware down to size, then there are some additional features that you can disable: 
  25. ```make
  26. SPACE_CADET_ENABLE = no
  27. GRAVE_ESC_ENABLE = no 
  28. MAGIC_ENABLE = no
  29. ```
  30. These features are enabled by default, but they may not be needed. Double check to make sure. The [Magic Keycodes](keycodes_magic) are the largest and control things like NKRO toggling, GUI and ALT/CTRL swapping, etc. Disabling them will disable those functions. See [Magic Functions](#magic-functions) for disabling related functions.
  32. If you use `sprintf` or `snprintf` functions you can save around ~400 Bytes by enabling this option.
  33. ```make
  34. AVR_USE_MINIMAL_PRINTF = yes
  35. ```
  37. 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:
  38. ```c
  39. sprintf(wpm_str, "%03d", get_current_wpm());
  40. snprintf(keylog_str, sizeof(keylog_str), "%dx%d, k%2d : %c");
  41. ```
  43. you will still need the standard implementation.
  45. ## `config.h` Settings
  47. 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.
  49. 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`:
  50. ```c
  51. #undef LOCKING_SUPPORT_ENABLE
  52. #undef LOCKING_RESYNC_ENABLE
  53. ```
  54. Oneshots. If you're not using these, you can disable the feature by adding this to your `config.h`: 
  55. ```c
  56. #define NO_ACTION_ONESHOT
  57. ```
  58. The same with tapping keys (mod tap, layer tap, etc)
  59. ```c
  60. #define NO_ACTION_TAPPING
  61. ```
  62. ## Audio Settings
  64. 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`:
  65. ```c
  66. #define NO_MUSIC_MODE
  67. ```
  68. And by adding this to your `rules.mk`
  69. ```make
  70. MUSIC_ENABLE = no
  71. ```
  73. ## Layers
  75. There are also some options for layers, that can reduce the firmware size. All of these settings are for your `config.h`.
  77. You can limit the number of layers that the firmware uses -- if you're using up to 8 layers in total:
  78. ```c
  79. #define LAYER_STATE_8BIT
  80. ```
  81. or if you require up to 16 layers instead:
  82. ```c
  83. #define LAYER_STATE_16BIT
  84. ```
  85. Or if you're not using layers at all, you can outright remove the functionality altogether:
  86. ```c
  87. #define NO_ACTION_LAYER
  88. ```
  90. ## Magic Functions
  92. 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:
  93. ```c
  94. #ifndef MAGIC_ENABLE
  95. uint16_t keycode_config(uint16_t keycode) {
  96.     return keycode;
  97. }
  98. #endif
  99. ```
  100. 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:
  101. ```c
  102. #ifndef MAGIC_ENABLE
  103. uint8_t mod_config(uint8_t mod) {
  104.     return mod;
  105. }
  106. #endif
  107. ```
  108. Both of them will overwrite the placeholder functions with a simple return statement to reduce firmware size.
  110. ## OLED tweaks
  112. 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.
  114. You can convert this:
  115. ```c
  116.     // OLD CODE
  117.     char wpm_str[4] = {0};
  118.     sprintf(wpm_str, "WPM: %03d", get_current_wpm());
  119.     oled_write(wpm_str, ' '), false);
  120. ```
  121. into this:
  122. ```c
  123.     // NEW CODE
  124.     oled_write_P(PSTR("WPM: "), false);
  125.     oled_write(get_u8_str(get_current_wpm(), ' '), false);
  126. ```
  127. which outputs `WPM:   5`. Or this: 
  128. ```c
  129.     // NEW CODE
  130.     oled_write_P(PSTR("WPM: "), false);
  131.     oled_write(get_u8_str(get_current_wpm(), '0'), false);
  132. ```
  133. which outputs `WPM: 005`.
  135. ## RGB Settings
  137. 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`:
  138. ```c
  139. #undef RGBLIGHT_ANIMATIONS
  140. #undef RGBLIGHT_EFFECT_BREATHING
  141. #undef RGBLIGHT_EFFECT_RAINBOW_MOOD
  142. #undef RGBLIGHT_EFFECT_RAINBOW_SWIRL
  143. #undef RGBLIGHT_EFFECT_SNAKE
  144. #undef RGBLIGHT_EFFECT_KNIGHT
  145. #undef RGBLIGHT_EFFECT_CHRISTMAS
  146. #undef RGBLIGHT_EFFECT_STATIC_GRADIENT
  147. #undef RGBLIGHT_EFFECT_RGB_TEST
  148. #undef RGBLIGHT_EFFECT_ALTERNATING
  149. #undef RGBLIGHT_EFFECT_TWINKLE
  150. ```
  152. 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`:
  153. ```c
  154. #undef ENABLE_RGB_MATRIX_ALPHAS_MODS
  155. #undef ENABLE_RGB_MATRIX_GRADIENT_UP_DOWN
  156. #undef ENABLE_RGB_MATRIX_GRADIENT_LEFT_RIGHT
  157. #undef ENABLE_RGB_MATRIX_BREATHING
  158. #undef ENABLE_RGB_MATRIX_BAND_SAT
  159. #undef ENABLE_RGB_MATRIX_BAND_VAL
  160. #undef ENABLE_RGB_MATRIX_BAND_PINWHEEL_SAT
  161. #undef ENABLE_RGB_MATRIX_BAND_PINWHEEL_VAL
  162. #undef ENABLE_RGB_MATRIX_BAND_SPIRAL_SAT
  163. #undef ENABLE_RGB_MATRIX_BAND_SPIRAL_VAL
  164. #undef ENABLE_RGB_MATRIX_CYCLE_ALL
  165. #undef ENABLE_RGB_MATRIX_CYCLE_LEFT_RIGHT
  166. #undef ENABLE_RGB_MATRIX_CYCLE_UP_DOWN
  167. #undef ENABLE_RGB_MATRIX_RAINBOW_MOVING_CHEVRON
  168. #undef ENABLE_RGB_MATRIX_CYCLE_OUT_IN
  169. #undef ENABLE_RGB_MATRIX_CYCLE_OUT_IN_DUAL
  170. #undef ENABLE_RGB_MATRIX_CYCLE_PINWHEEL
  171. #undef ENABLE_RGB_MATRIX_CYCLE_SPIRAL
  172. #undef ENABLE_RGB_MATRIX_DUAL_BEACON
  173. #undef ENABLE_RGB_MATRIX_RAINBOW_BEACON
  174. #undef ENABLE_RGB_MATRIX_RAINBOW_PINWHEELS
  175. #undef ENABLE_RGB_MATRIX_FLOWER_BLOOMING
  176. #undef ENABLE_RGB_MATRIX_RAINDROPS
  177. #undef ENABLE_RGB_MATRIX_JELLYBEAN_RAINDROPS
  178. #undef ENABLE_RGB_MATRIX_HUE_BREATHING
  179. #undef ENABLE_RGB_MATRIX_HUE_PENDULUM
  180. #undef ENABLE_RGB_MATRIX_HUE_WAVE
  181. #undef ENABLE_RGB_MATRIX_PIXEL_FRACTAL
  182. #undef ENABLE_RGB_MATRIX_PIXEL_FLOW
  183. #undef ENABLE_RGB_MATRIX_PIXEL_RAIN
  185. #undef ENABLE_RGB_MATRIX_TYPING_HEATMAP
  186. #undef ENABLE_RGB_MATRIX_DIGITAL_RAIN
  188. #undef ENABLE_RGB_MATRIX_SOLID_REACTIVE_SIMPLE
  189. #undef ENABLE_RGB_MATRIX_SOLID_REACTIVE
  190. #undef ENABLE_RGB_MATRIX_SOLID_REACTIVE_WIDE
  191. #undef ENABLE_RGB_MATRIX_SOLID_REACTIVE_MULTIWIDE
  192. #undef ENABLE_RGB_MATRIX_SOLID_REACTIVE_CROSS
  193. #undef ENABLE_RGB_MATRIX_SOLID_REACTIVE_MULTICROSS
  194. #undef ENABLE_RGB_MATRIX_SOLID_REACTIVE_NEXUS
  195. #undef ENABLE_RGB_MATRIX_SOLID_REACTIVE_MULTINEXUS
  196. #undef ENABLE_RGB_MATRIX_SPLASH
  197. #undef ENABLE_RGB_MATRIX_MULTISPLASH
  198. #undef ENABLE_RGB_MATRIX_SOLID_SPLASH
  199. #undef ENABLE_RGB_MATRIX_SOLID_MULTISPLASH
  200. ```
  202. # Final Thoughts
  204. If you've done all of this, and your firmware is still too large, then it is time to consider making the switch to ARM. There are a number of Pro Micro replacements with an ARM controller:
  205. * [Bonsai C](https://github.com/customMK/Bonsai-C) (Open Source, DIY/PCBA)
  206. * [STeMCell](https://github.com/megamind4089/STeMCell) (Open Source, DIY/PCBA)
  207. * [Adafruit KB2040](https://learn.adafruit.com/adafruit-kb2040)
  208. * [SparkFun Pro Micro - RP2040](https://www.sparkfun.com/products/18288)
  209. * [Blok](https://boardsource.xyz/store/628b95b494dfa308a6581622)
  210. * [Elite-Pi](https://keeb.io/products/elite-pi-usb-c-pro-micro-replacement-rp2040)
  211. * [0xCB Helios](https://keeb.supply/products/0xcb-helios) ([Open Source](https://github.com/0xCB-dev/0xCB-Helios), DIY/PCBA/Shop)
  212. * [Liatris](https://splitkb.com/products/liatris)
  213. * [Imera](https://splitkb.com/products/imera)
  214. * [Michi](https://github.com/ci-bus/michi-promicro-rp2040)
  215. * [Proton C](https://qmk.fm/proton-c/) (out of stock)
  217. There are other, non-Pro Micro compatible boards out there. The most popular being:
  218. * [WeAct Blackpill F411](https://www.aliexpress.com/item/1005001456186625.html) (~$6 USD)