Output I2S audio with PIO/DMA

Requires a MAX98357A amplifier and a 2W 8ohms speaker
2022-12-02 17:24:39 +00:00
parent a9f54dc37d
commit 29a04ad832
8 changed files with 285 additions and 31 deletions
@@ -0,0 +1,100 @@
+/**
+ * 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);
+}