1 files changed, 164 insertions, 0 deletions

diff --git a/platforms/chibios/drivers/audio_pwm_software.c b/platforms/chibios/drivers/audio_pwm_software.c
new file mode 100644
index 000000000..15c3e98b6
--- /dev/null
+++ b/platforms/chibios/drivers/audio_pwm_software.c
@@ -0,0 +1,164 @@
+/* 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 any given output pin in software
+- a pwm callback is used to set/clear the configured pin.
+
+ */
+#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 void pwm_audio_period_callback(PWMDriver *pwmp);
+static void pwm_audio_channel_interrupt_callback(PWMDriver *pwmp);
+
+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 = pwm_audio_period_callback,
+    .channels =
+        {
+            // software-PWM just needs another callback on any channel
+            {PWM_OUTPUT_ACTIVE_HIGH, pwm_audio_channel_interrupt_callback}, /* channel 0 -> TIMx_CH1 */
+            {PWM_OUTPUT_DISABLED, NULL},                                    /* channel 1 -> TIMx_CH2 */
+            {PWM_OUTPUT_DISABLED, NULL},                                    /* channel 2 -> TIMx_CH3 */
+            {PWM_OUTPUT_DISABLED, NULL}                                     /* channel 3 -> TIMx_CH4 */
+        },
+};
+
+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);
+
+    pwmEnablePeriodicNotification(&AUDIO_PWM_DRIVER);
+    pwmEnableChannelNotification(&AUDIO_PWM_DRIVER, AUDIO_PWM_CHANNEL - 1);
+}
+
+void channel_1_stop(void) {
+    pwmStop(&AUDIO_PWM_DRIVER);
+
+    palClearLine(AUDIO_PIN);  // leave the line low, after last note was played
+
+#if defined(AUDIO_PIN_ALT) && defined(AUDIO_PIN_ALT_AS_NEGATIVE)
+    palClearLine(AUDIO_PIN_ALT);  // leave the line low, after last note was played
+#endif
+}
+
+// generate a PWM signal on any pin, not necessarily the one connected to the timer
+static void pwm_audio_period_callback(PWMDriver *pwmp) {
+    (void)pwmp;
+    palClearLine(AUDIO_PIN);
+
+#if defined(AUDIO_PIN_ALT) && defined(AUDIO_PIN_ALT_AS_NEGATIVE)
+    palSetLine(AUDIO_PIN_ALT);
+#endif
+}
+static void pwm_audio_channel_interrupt_callback(PWMDriver *pwmp) {
+    (void)pwmp;
+    if (channel_1_frequency > 0) {
+        palSetLine(AUDIO_PIN);  // generate a PWM signal on any pin, not necessarily the one connected to the timer
+#if defined(AUDIO_PIN_ALT) && defined(AUDIO_PIN_ALT_AS_NEGATIVE)
+        palClearLine(AUDIO_PIN_ALT);
+#endif
+    }
+}
+
+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 anything
+    */
+    .frequency = 60 * 64,
+    .callback  = gpt_callback,
+};
+
+void audio_driver_initialize(void) {
+    pwmStart(&AUDIO_PWM_DRIVER, &pwmCFG);
+
+    palSetLineMode(AUDIO_PIN, PAL_MODE_OUTPUT_PUSHPULL);
+    palClearLine(AUDIO_PIN);
+
+#if defined(AUDIO_PIN_ALT) && defined(AUDIO_PIN_ALT_AS_NEGATIVE)
+    palSetLineMode(AUDIO_PIN_ALT, PAL_MODE_OUTPUT_PUSHPULL);
+    palClearLine(AUDIO_PIN_ALT);
+#endif
+
+    pwmEnablePeriodicNotification(&AUDIO_PWM_DRIVER);  // enable pwm callbacks
+    pwmEnableChannelNotification(&AUDIO_PWM_DRIVER, AUDIO_PWM_CHANNEL - 1);
+
+    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);
+    }
+}