Make ARM Audio max volume configurable (#4540)

* Make ARM Audio max volume configurable

* Update docs/feature_audio.md

Co-Authored-By: drashna <drashna@live.com>

* Update docs/feature_audio.md

Co-Authored-By: drashna <drashna@live.com>

docs/feature_audio.md

@@ -65,6 +65,13 @@ The available keycodes for audio are:
 * `AU_OFF` - Turn audio mode off
 * `AU_TOG` - Toggle audio mode
 
+## ARM Audio Volume
+
+For ARM devices, you can adjust the DAC sample values. If your board is too loud for you or your coworkers, you can set the max using `DAC_SAMPLE_MAX` in your `config.h`:
+
+```c
+#define DAC_SAMPLE_MAX 65535U
+```
 
 ## Music Mode
 

quantum/audio/audio_arm.c

@@ -80,7 +80,9 @@ float startup_song[][2] = STARTUP_SONG;
 static void gpt_cb8(GPTDriver *gptp);
 
 #define DAC_BUFFER_SIZE 720
+#ifndef DAC_SAMPLE_MAX
 #define DAC_SAMPLE_MAX  65535U
+#endif
 
 #define START_CHANNEL_1() gptStart(&GPTD6, &gpt6cfg1); \
     gptStartContinuous(&GPTD6, 2U)