117 lines
3.8 KiB
C
117 lines
3.8 KiB
C
// Copyright 2022 Stefan Kerkmann
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// Copyright 2020 Jack Humbert
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// Copyright 2020 JohSchneider
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// SPDX-License-Identifier: GPL-2.0-or-later
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// Audio Driver: PWM the duty-cycle is always kept at 50%, and the pwm-period is
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// adjusted to match the frequency of a note to be played back. This driver uses
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// the chibios-PWM system to produce a square-wave on specific output pins that
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// are connected to the PWM hardware. The hardware directly toggles the pin via
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// its alternate function. see your MCUs data-sheet for which pin can be driven
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// by what timer - looking for TIMx_CHy and the corresponding alternate
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// function.
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#include "audio.h"
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#include "ch.h"
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#include "hal.h"
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#if !defined(AUDIO_PIN)
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# error "Audio feature enabled, but no pin selected - see docs/feature_audio under the ARM PWM settings"
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#endif
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#if !defined(AUDIO_PWM_COUNTER_FREQUENCY)
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# define AUDIO_PWM_COUNTER_FREQUENCY 100000
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#endif
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extern bool playing_note;
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extern bool playing_melody;
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extern uint8_t note_timbre;
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static PWMConfig pwmCFG = {.frequency = AUDIO_PWM_COUNTER_FREQUENCY, /* PWM clock frequency */
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.period = 2,
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.callback = NULL,
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.channels = {[(AUDIO_PWM_CHANNEL - 1)] = {.mode = PWM_OUTPUT_ACTIVE_HIGH, .callback = NULL}}};
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static float channel_1_frequency = 0.0f;
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void channel_1_set_frequency(float freq) {
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channel_1_frequency = freq;
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if (freq <= 0.0) {
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// a pause/rest has freq=0
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return;
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}
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pwmcnt_t period = (pwmCFG.frequency / freq);
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chSysLockFromISR();
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pwmChangePeriodI(&AUDIO_PWM_DRIVER, period);
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pwmEnableChannelI(&AUDIO_PWM_DRIVER, AUDIO_PWM_CHANNEL - 1,
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// adjust the duty-cycle so that the output is for 'note_timbre' duration HIGH
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PWM_PERCENTAGE_TO_WIDTH(&AUDIO_PWM_DRIVER, (100 - note_timbre) * 100));
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chSysUnlockFromISR();
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}
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float channel_1_get_frequency(void) {
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return channel_1_frequency;
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}
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void channel_1_start(void) {
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pwmStop(&AUDIO_PWM_DRIVER);
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pwmStart(&AUDIO_PWM_DRIVER, &pwmCFG);
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}
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void channel_1_stop(void) {
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pwmStop(&AUDIO_PWM_DRIVER);
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}
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static virtual_timer_t audio_vt;
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static void audio_callback(virtual_timer_t *vtp, void *p);
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// a regular timer task, that checks the note to be currently played and updates
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// the pwm to output that frequency.
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static void audio_callback(virtual_timer_t *vtp, void *p) {
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float freq; // TODO: freq_alt
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if (audio_update_state()) {
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freq = audio_get_processed_frequency(0); // freq_alt would be index=1
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channel_1_set_frequency(freq);
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}
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chSysLockFromISR();
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chVTSetI(&audio_vt, TIME_MS2I(16), audio_callback, NULL);
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chSysUnlockFromISR();
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}
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void audio_driver_initialize(void) {
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pwmStart(&AUDIO_PWM_DRIVER, &pwmCFG);
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// connect the AUDIO_PIN to the PWM hardware
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#if defined(USE_GPIOV1) // STM32F103C8, RP2040
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palSetLineMode(AUDIO_PIN, AUDIO_PWM_PAL_MODE);
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#else // GPIOv2 (or GPIOv3 for f4xx, which is the same/compatible at this command)
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palSetLineMode(AUDIO_PIN, PAL_MODE_ALTERNATE(AUDIO_PWM_PAL_MODE));
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#endif
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chVTObjectInit(&audio_vt);
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}
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void audio_driver_start(void) {
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channel_1_stop();
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channel_1_start();
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if ((playing_note || playing_melody) && !chVTIsArmed(&audio_vt)) {
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// a whole note is one beat, which is - per definition in
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// musical_notes.h - set to 64 the longest note is
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// BREAVE_DOT=128+64=192, the shortest SIXTEENTH=4 the tempo (which
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// might vary!) is in bpm (beats per minute) therefore: if the timer
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// ticks away at 64Hz (~16.6ms) audio_update_state is called just often
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// enough to not miss any notes
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chVTSet(&audio_vt, TIME_MS2I(16), audio_callback, NULL);
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}
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}
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void audio_driver_stop(void) {
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channel_1_stop();
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chVTReset(&audio_vt);
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}
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