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/* Copyright 2020 Jack Humbert
* Copyright 2020 JohSchneider
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
Audio Driver: PWM
the duty-cycle is always kept at 50%, and the pwm-period is adjusted to match the frequency of a note to be played back.
this driver uses the chibios-PWM system to produce a square-wave on specific output pins that are connected to the PWM hardware.
The hardware directly toggles the pin via its alternate function. see your MCUs data-sheet for which pin can be driven by what timer - looking for TIMx_CHy and the corresponding alternate function.
*/
#include "audio.h"
#include "ch.h"
#include "hal.h"
#if !defined(AUDIO_PIN)
# error "Audio feature enabled, but no pin selected - see docs/feature_audio under the ARM PWM settings"
#endif
extern bool playing_note;
extern bool playing_melody;
extern uint8_t note_timbre;
static PWMConfig pwmCFG = {
.frequency = 100000, /* PWM clock frequency */
// CHIBIOS-BUG? can't set the initial period to <2, or the pwm (hard or software) takes ~130ms with .frequency=500000 for a pwmChangePeriod to take effect; with no output=silence in the meantime
.period = 2, /* initial PWM period (in ticks) 1S (1/10kHz=0.1mS 0.1ms*10000 ticks=1S) */
.callback = NULL, /* no callback, the hardware directly toggles the pin */
.channels =
{
#if AUDIO_PWM_CHANNEL == 4
{PWM_OUTPUT_DISABLED, NULL}, /* channel 0 -> TIMx_CH1 */
{PWM_OUTPUT_DISABLED, NULL}, /* channel 1 -> TIMx_CH2 */
{PWM_OUTPUT_DISABLED, NULL}, /* channel 2 -> TIMx_CH3 */
{PWM_OUTPUT_ACTIVE_HIGH, NULL} /* channel 3 -> TIMx_CH4 */
#elif AUDIO_PWM_CHANNEL == 3
{PWM_OUTPUT_DISABLED, NULL},
{PWM_OUTPUT_DISABLED, NULL},
{PWM_OUTPUT_ACTIVE_HIGH, NULL}, /* TIMx_CH3 */
{PWM_OUTPUT_DISABLED, NULL}
#elif AUDIO_PWM_CHANNEL == 2
{PWM_OUTPUT_DISABLED, NULL},
{PWM_OUTPUT_ACTIVE_HIGH, NULL}, /* TIMx_CH2 */
{PWM_OUTPUT_DISABLED, NULL},
{PWM_OUTPUT_DISABLED, NULL}
#else /*fallback to CH1 */
{PWM_OUTPUT_ACTIVE_HIGH, NULL}, /* TIMx_CH1 */
{PWM_OUTPUT_DISABLED, NULL},
{PWM_OUTPUT_DISABLED, NULL},
{PWM_OUTPUT_DISABLED, NULL}
#endif
},
};
static float channel_1_frequency = 0.0f;
void channel_1_set_frequency(float freq) {
channel_1_frequency = freq;
if (freq <= 0.0) // a pause/rest has freq=0
return;
pwmcnt_t period = (pwmCFG.frequency / freq);
pwmChangePeriod(&AUDIO_PWM_DRIVER, period);
pwmEnableChannel(&AUDIO_PWM_DRIVER, AUDIO_PWM_CHANNEL - 1,
// adjust the duty-cycle so that the output is for 'note_timbre' duration HIGH
PWM_PERCENTAGE_TO_WIDTH(&AUDIO_PWM_DRIVER, (100 - note_timbre) * 100));
}
float channel_1_get_frequency(void) { return channel_1_frequency; }
void channel_1_start(void) {
pwmStop(&AUDIO_PWM_DRIVER);
pwmStart(&AUDIO_PWM_DRIVER, &pwmCFG);
}
void channel_1_stop(void) { pwmStop(&AUDIO_PWM_DRIVER); }
static void gpt_callback(GPTDriver *gptp);
GPTConfig gptCFG = {
/* a whole note is one beat, which is - per definition in musical_notes.h - set to 64
the longest note is BREAVE_DOT=128+64=192, the shortest SIXTEENTH=4
the tempo (which might vary!) is in bpm (beats per minute)
therefore: if the timer ticks away at .frequency = (60*64)Hz,
and the .interval counts from 64 downwards - audio_update_state is
called just often enough to not miss any notes
*/
.frequency = 60 * 64,
.callback = gpt_callback,
};
void audio_driver_initialize(void) {
pwmStart(&AUDIO_PWM_DRIVER, &pwmCFG);
// connect the AUDIO_PIN to the PWM hardware
#if defined(USE_GPIOV1) // STM32F103C8
palSetLineMode(AUDIO_PIN, PAL_MODE_ALTERNATE_PUSHPULL);
#else // GPIOv2 (or GPIOv3 for f4xx, which is the same/compatible at this command)
palSetLineMode(AUDIO_PIN, PAL_MODE_ALTERNATE(AUDIO_PWM_PAL_MODE));
#endif
gptStart(&AUDIO_STATE_TIMER, &gptCFG);
}
void audio_driver_start(void) {
channel_1_stop();
channel_1_start();
if (playing_note || playing_melody) {
gptStartContinuous(&AUDIO_STATE_TIMER, 64);
}
}
void audio_driver_stop(void) {
channel_1_stop();
gptStopTimer(&AUDIO_STATE_TIMER);
}
/* a regular timer task, that checks the note to be currently played
* and updates the pwm to output that frequency
*/
static void gpt_callback(GPTDriver *gptp) {
float freq; // TODO: freq_alt
if (audio_update_state()) {
freq = audio_get_processed_frequency(0); // freq_alt would be index=1
channel_1_set_frequency(freq);
}
}
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