1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
|
/* 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 "gpio.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);
}
}
|
