I'm currently trying to read audio data from a PCM4222 ADC using I2S. I managed to get the ESP to read correct data from the ADC, however it seems like the ESP is skipping some samples, see image below.
- Screenshot 2024-02-04 012256.png (53.83 KiB) Viewed 424 times
This seems to always happen somewhere between sample number 400 and 500 and I cannot for the life of me figure out what the issue is.
Furthermore, is there a way to ensure seamless consecutive readouts? It seems like there also are a handful of samples missing between individual readouts.
Minimal working example:
Code: Select all
// Include I2S library
#include <driver/i2s.h>
// Define I2S settings
#define I2S_BCK_PIN 14
#define I2S_LRCK_PIN 25
#define I2S_DATA_PIN 26
#define SAMPLE_RATE 48000
#define DMA_BUF_LEN 1024
#define DMA_BUF_COUNT 2
void setup()
{
// Initialize serial communication
Serial.begin(115200);
// Configure I2S
i2s_config_t i2s_config = {
.mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX),
.sample_rate = SAMPLE_RATE,
.bits_per_sample = I2S_BITS_PER_SAMPLE_32BIT,
.channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
.communication_format = (i2s_comm_format_t)(I2S_COMM_FORMAT_I2S | I2S_COMM_FORMAT_I2S_LSB),
.intr_alloc_flags = 0,
.dma_buf_count = DMA_BUF_COUNT,
.dma_buf_len = DMA_BUF_LEN
};
// Define I2S pins
i2s_pin_config_t pin_config = {
.bck_io_num = I2S_BCK_PIN,
.ws_io_num = I2S_LRCK_PIN,
.data_out_num = -1,
.data_in_num = I2S_DATA_PIN
};
// Initialize I2S communication
i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);
i2s_set_pin(I2S_NUM_0, &pin_config);
}
void loop()
{
// Define variables
size_t bytesRead;
int32_t* i2sData = (int32_t*)malloc(2 * DMA_BUF_LEN * sizeof(int32_t));
// Read data for both left and right channels
i2s_read(I2S_NUM_0, i2sData, 2 * DMA_BUF_LEN * sizeof(int32_t), &bytesRead, portMAX_DELAY);
for (uint16_t i = 0; i < DMA_BUF_LEN; ++i)
{
// Discard first bit and last 7 bits
i2sData[2 * i] = (i2sData[2 * i] >> 7) & 0xFFFFFF;
i2sData[2 * i + 1] = (i2sData[2 * i + 1] >> 7) & 0xFFFFFF;
// Sign extend
i2sData[2 * i] <<= 8;
i2sData[2 * i] >>= 8;
i2sData[2 * i + 1] <<= 8;
i2sData[2 * i + 1] >>= 8;
// Print right channel data for debugging purposes
Serial.print(i); Serial.print("\t"); Serial.println(i2sData[2 * i + 1]);
}
Serial.print("");
// De-allocate memory used for data samples
free(i2sData);
}