sine_wave.c

/**
 * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <stdio.h>
#include <math.h>

#if PICO_ON_DEVICE

#include "hardware/clocks.h"
#include "hardware/structs/clocks.h"

#endif

#include "pico/stdlib.h"

#if USE_AUDIO_I2S

#include "pico/audio_i2s.h"

#if PICO_ON_DEVICE
#include "pico/binary_info.h"
bi_decl(bi_3pins_with_names(PICO_AUDIO_I2S_DATA_PIN, "I2S DIN", PICO_AUDIO_I2S_CLOCK_PIN_BASE, "I2S BCK", PICO_AUDIO_I2S_CLOCK_PIN_BASE+1, "I2S LRCK"));
#endif

#elif USE_AUDIO_PWM
#include "pico/audio_pwm.h"
#elif USE_AUDIO_SPDIF
#include "pico/audio_spdif.h"
#endif

#define SINE_WAVE_TABLE_LEN 2048
#define SAMPLES_PER_BUFFER 256

static int16_t sine_wave_table[SINE_WAVE_TABLE_LEN];

struct audio_buffer_pool *init_audio() {

    static audio_format_t audio_format = {
            .format = AUDIO_BUFFER_FORMAT_PCM_S16,
#if USE_AUDIO_SPDIF
            .sample_freq = 44100,
#else
            .sample_freq = 24000,
#endif
            .channel_count = 1,
    };

    static struct audio_buffer_format producer_format = {
            .format = &audio_format,
            .sample_stride = 2
    };

    struct audio_buffer_pool *producer_pool = audio_new_producer_pool(&producer_format, 3,
                                                                      SAMPLES_PER_BUFFER); // todo correct size
    bool __unused ok;
    const struct audio_format *output_format;
#if USE_AUDIO_I2S
    struct audio_i2s_config config = {
            .data_pin = PICO_AUDIO_I2S_DATA_PIN,
            .clock_pin_base = PICO_AUDIO_I2S_CLOCK_PIN_BASE,
            .dma_channel = 0,
            .pio_sm = 0,
    };

    output_format = audio_i2s_setup(&audio_format, &config);
    if (!output_format) {
        panic("PicoAudio: Unable to open audio device.\n");
    }

    ok = audio_i2s_connect(producer_pool);
    assert(ok);
    audio_i2s_set_enabled(true);
#elif USE_AUDIO_PWM
    output_format = audio_pwm_setup(&audio_format, -1, &default_mono_channel_config);
    if (!output_format) {
        panic("PicoAudio: Unable to open audio device.\n");
    }
    ok = audio_pwm_default_connect(producer_pool, false);
    assert(ok);
    audio_pwm_set_enabled(true);
#elif USE_AUDIO_SPDIF
    output_format = audio_spdif_setup(&audio_format, &audio_spdif_default_config);
    if (!output_format) {
        panic("PicoAudio: Unable to open audio device.\n");
    }
    //ok = audio_spdif_connect(producer_pool);
    ok = audio_spdif_connect(producer_pool);
    assert(ok);
    audio_spdif_set_enabled(true);
#endif
    return producer_pool;
}

int main() {
#if PICO_ON_DEVICE
#if USE_AUDIO_PWM
    set_sys_clock_48mhz();
#endif
#endif

    stdio_init_all();

    for (int i = 0; i < SINE_WAVE_TABLE_LEN; i++) {
        sine_wave_table[i] = 32767 * cosf(i * 2 * (float) (M_PI / SINE_WAVE_TABLE_LEN));
    }

    struct audio_buffer_pool *ap = init_audio();
    uint32_t step = 0x200000;
    uint32_t pos = 0;
    uint32_t pos_max = 0x10000 * SINE_WAVE_TABLE_LEN;
    uint vol = 128;
    while (true) {
#if USE_AUDIO_PWM
        enum audio_correction_mode m = audio_pwm_get_correction_mode();
#endif
        int c = getchar_timeout_us(0);
        if (c >= 0) {
            if (c == '-' && vol) vol -= 4;
            if ((c == '=' || c == '+') && vol < 255) vol += 4;
            if (c == '[' && step > 0x10000) step -= 0x10000;
            if (c == ']' && step < (SINE_WAVE_TABLE_LEN / 16) * 0x20000) step += 0x10000;
            if (c == 'q') break;
#if USE_AUDIO_PWM
            if (c == 'c') {
                bool done = false;
                while (!done) {
                    if (m == none) m = fixed_dither;
                    else if (m == fixed_dither) m = dither;
                    else if (m == dither) m = noise_shaped_dither;
                    else if (m == noise_shaped_dither) m = none;
                    done = audio_pwm_set_correction_mode(m);
                }
            }
            printf("vol = %d, step = %d mode = %d      \r", vol, step >>16, m);
#else
            printf("vol = %d, step = %d      \r", vol, step >> 16);
#endif
        }
        struct audio_buffer *buffer = take_audio_buffer(ap, true);
        int16_t *samples = (int16_t *) buffer->buffer->bytes;
        for (uint i = 0; i < buffer->max_sample_count; i++) {
            samples[i] = (vol * sine_wave_table[pos >> 16u]) >> 8u;
            pos += step;
            if (pos >= pos_max) pos -= pos_max;
        }
        buffer->sample_count = buffer->max_sample_count;
        give_audio_buffer(ap, buffer);
    }
    puts("\n");
    return 0;
}