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Output I2S audio with PIO/DMA

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Requires a MAX98357A amplifier and a 2W 8ohms speaker
This commit is contained in:
Vincent Mistler
2022-12-02 17:24:39 +00:00
parent a9f54dc37d
commit 29a04ad832
8 changed files with 285 additions and 31 deletions
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ext/i2s/audio_i2s.pio
+63
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@@ -0,0 +1,63 @@
;
; Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
;
; SPDX-License-Identifier: BSD-3-Clause
;
; Transmit a mono or stereo I2S audio stream as stereo
; This is 16 bits per sample; can be altered by modifying the "set" params,
; or made programmable by replacing "set x" with "mov x, y" and using Y as a config register.
;
; Autopull must be enabled, with threshold set to 32.
; Since I2S is MSB-first, shift direction should be to left.
; Hence the format of the FIFO word is:
;
; | 31 : 16 | 15 : 0 |
; | sample ws=0 | sample ws=1 |
;
; Data is output at 1 bit per clock. Use clock divider to adjust frequency.
; Fractional divider will probably be needed to get correct bit clock period,
; but for common syslck freqs this should still give a constant word select period.
;
; One output pin is used for the data output.
; Two side-set pins are used. Bit 0 is clock, bit 1 is word select.
; Send 16 bit words to the PIO for mono, 32 bit words for stereo
.program audio_i2s
.side_set 2
; /--- LRCLK
; |/-- BCLK
bitloop1: ; ||
out pins, 1 side 0b10
jmp x-- bitloop1 side 0b11
out pins, 1 side 0b00
set x, 14 side 0b01
bitloop0:
out pins, 1 side 0b00
jmp x-- bitloop0 side 0b01
out pins, 1 side 0b10
public entry_point:
set x, 14 side 0b11
% c-sdk {
static inline void audio_i2s_program_init(PIO pio, uint sm, uint offset, uint data_pin, uint clock_pin_base) {
pio_sm_config sm_config = audio_i2s_program_get_default_config(offset);
sm_config_set_out_pins(&sm_config, data_pin, 1);
sm_config_set_sideset_pins(&sm_config, clock_pin_base);
sm_config_set_out_shift(&sm_config, false, true, 32);
pio_sm_init(pio, sm, offset, &sm_config);
uint pin_mask = (1u << data_pin) | (3u << clock_pin_base);
pio_sm_set_pindirs_with_mask(pio, sm, pin_mask, pin_mask);
pio_sm_set_pins(pio, sm, 0); // clear pins
pio_sm_exec(pio, sm, pio_encode_jmp(offset + audio_i2s_offset_entry_point));
}
%}
ext/i2s/i2s.c
+100
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/**
* MIT License
*
* Copyright (c) 2022 Vincent Mistler
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include "i2s.h"
i2s_config_t i2s_get_default_config(void) {
i2s_config_t i2s_config = {
.sample_freq = 44100,
.channel_count = 2,
.data_pin = 26,
.clock_pin_base = 27,
.pio = pio0,
.sm = 0,
.dma_channel = 0,
.dma_buf = NULL,
.dma_trans_count = 0,
};
return i2s_config;
}
void i2s_init(i2s_config_t *i2s_config) {
uint8_t func=GPIO_FUNC_PIO0; // TODO: GPIO_FUNC_PIO0 for pio0 or GPIO_FUNC_PIO1 for pio1
gpio_set_function(i2s_config->data_pin, GPIO_FUNC_PIO0);
gpio_set_function(i2s_config->clock_pin_base, GPIO_FUNC_PIO0);
gpio_set_function(i2s_config->clock_pin_base+1, GPIO_FUNC_PIO0);
i2s_config->sm = pio_claim_unused_sm(i2s_config->pio, true);
uint offset = pio_add_program(i2s_config->pio, &audio_i2s_program);
audio_i2s_program_init(i2s_config->pio, i2s_config->sm , offset, i2s_config->data_pin , i2s_config->clock_pin_base);
// Set PIO clock
uint32_t system_clock_frequency = clock_get_hz(clk_sys);
uint32_t divider = system_clock_frequency * 4 / i2s_config->sample_freq; // avoid arithmetic overflow
pio_sm_set_clkdiv_int_frac(i2s_config->pio, i2s_config->sm , divider >> 8u, divider & 0xffu);
pio_sm_set_enabled(i2s_config->pio, i2s_config->sm, false);
// Allocate memory for the DMA buffer
i2s_config->dma_buf=malloc(i2s_config->dma_trans_count*sizeof(uint32_t));
// Direct Memory Access setup
i2s_config->dma_channel = dma_claim_unused_channel(true);
dma_channel_config dma_config = dma_channel_get_default_config(i2s_config->dma_channel);
channel_config_set_read_increment(&dma_config, true);
channel_config_set_write_increment(&dma_config, false);
channel_config_set_dreq(&dma_config, pio_get_dreq(i2s_config->pio, i2s_config->sm, true));
channel_config_set_transfer_data_size(&dma_config, DMA_SIZE_32);
dma_channel_configure(i2s_config->dma_channel,
&dma_config,
&(i2s_config->pio->txf[i2s_config->sm]), // Destination pointer
i2s_config->dma_buf, // Source pointer
i2s_config->dma_trans_count, // Number of 32 bits words to transfer
false // Start immediately
);
pio_sm_set_enabled(i2s_config->pio, i2s_config->sm , true);
}
void i2s_write(const i2s_config_t *i2s_config,const int16_t *samples,const size_t len) {
for(size_t i=0;i<len;i++) {
pio_sm_put_blocking(i2s_config->pio, i2s_config->sm, (uint32_t)samples[i]);
}
}
// Write samples to DMA buffer and initiate DMA transfer (non blocking)
void i2s_dma_write(i2s_config_t *i2s_config,const int16_t *samples) {
// Wait the completion of the previous DMA transfer
dma_channel_wait_for_finish_blocking(i2s_config->dma_channel);
// Copy samples into the DMA buffer
memcpy(i2s_config->dma_buf,samples,i2s_config->dma_trans_count*sizeof(int32_t));
// Initiate the DMA transfer
dma_channel_transfer_from_buffer_now(i2s_config->dma_channel,
i2s_config->dma_buf,
i2s_config->dma_trans_count);
}
ext/i2s/i2s.h
+52
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@@ -0,0 +1,52 @@
/**
* MIT License
*
* Copyright (c) 2022 Vincent Mistler
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#pragma once
#include <stdlib.h>
#include <string.h>
#include <hardware/pio.h>
#include <hardware/clocks.h>
#include <hardware/dma.h>
#include "audio_i2s.pio.h"
typedef struct i2s_config
{
uint32_t sample_freq;
uint16_t channel_count;
uint8_t data_pin;
uint8_t clock_pin_base;
PIO pio;
uint8_t sm;
uint8_t dma_channel;
uint16_t dma_trans_count;
uint16_t *dma_buf;
} i2s_config_t;
i2s_config_t i2s_get_default_config(void);
void i2s_init(i2s_config_t *i2s_config);
void i2s_write(const i2s_config_t *i2s_config,const int16_t *samples,const size_t len);
void i2s_dma_write(i2s_config_t *i2s_config,const int16_t *samples);
ext/minigb_apu/minigb_apu.c
+5 -7
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@@ -365,19 +365,17 @@ static void update_noise(int16_t *samples)
/**
* SDL2 style audio callback function.
*/
void audio_callback(void *userdata, uint8_t *stream, int len)
void audio_callback(void *userdata, int16_t *stream, size_t len)
{
int16_t *samples = (int16_t *)stream;
/* Appease unused variable warning. */
(void)userdata;
memset(stream, 0, len);
update_square(samples, 0);
update_square(samples, 1);
update_wave(samples);
update_noise(samples);
update_square(stream, 0);
update_square(stream, 1);
update_wave(stream);
update_noise(stream);
}
static void chan_trigger(uint_fast8_t i)
ext/minigb_apu/minigb_apu.h
+3 -2
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@@ -9,19 +9,20 @@
#include <stdint.h>
#define AUDIO_SAMPLE_RATE 32768
#define AUDIO_SAMPLE_RATE 44100
#define DMG_CLOCK_FREQ 4194304.0
#define SCREEN_REFRESH_CYCLES 70224.0
#define VERTICAL_SYNC (DMG_CLOCK_FREQ/SCREEN_REFRESH_CYCLES)
#define AUDIO_SAMPLES ((unsigned)(AUDIO_SAMPLE_RATE / VERTICAL_SYNC))
#define AUDIO_BUFFER_SIZE_BYTES (AUDIO_SAMPLES*4)
/**
* Fill allocated buffer "data" with "len" number of 32-bit floating point
* samples (native endian order) in stereo interleaved format.
*/
void audio_callback(void *ptr, uint8_t *data, int len);
void audio_callback(void *ptr, int16_t *data, size_t len);
/**
* Read audio register at given address "addr".