I2s full duplex mode

[ana7233]

Hi, im doing a project using acoustics to detect defects in pipes and am trying to set up a code to get a microphone and speaker working simultaneously. I have no previous arduino coding experience so unfortunately i have had to use chat gpt. The speaker is working fine but the mic isnt working- the serial monitor shows the axes moving but sound remains at zero. Here is the code: #include "driver/i2s_std.h"
#include "driver/gpio.h"
#include <Arduino.h>

// I2S channel handles
i2s_chan_handle_t tx_handle; // Speaker (TX)
i2s_chan_handle_t rx_handle; // Microphone (RX)

void setup() {
Serial.begin(115200);

// === Allocate I2S Channels (Full-Duplex) ===
i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_NUM_0, I2S_ROLE_MASTER);
i2s_new_channel(&chan_cfg, &tx_handle, &rx_handle);

// === Configure I2S TX & RX (Same Clock) ===
i2s_std_config_t std_cfg = {
    .clk_cfg = I2S_STD_CLK_DEFAULT_CONFIG(16000), // 🔹 Lowered to 16 kHz for SPH0645
    .slot_cfg = I2S_STD_PHILIPS_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO), // 🔹 Use MONO Mode (Left Channel Only)
    .gpio_cfg = {
        .mclk = I2S_GPIO_UNUSED,
        .bclk = GPIO_NUM_4,  // 🔄 Shared Bit Clock
        .ws = GPIO_NUM_5,    // 🔄 Shared Word Select (LRCLK)
        .dout = GPIO_NUM_18, // 🔊 Speaker (TX)
        .din = GPIO_NUM_19,  // 🎤 Microphone (RX)
        .invert_flags = {
            .mclk_inv = false,
            .bclk_inv = false,
            .ws_inv = false,
        },
    },
};

// Initialize TX & RX channels
i2s_channel_init_std_mode(tx_handle, &std_cfg);
i2s_channel_init_std_mode(rx_handle, &std_cfg);

// Enable TX & RX
i2s_channel_enable(tx_handle);
i2s_channel_enable(rx_handle);

Serial.println("I2S Full-Duplex Initialized!");

// Create tasks for speaker and microphone
xTaskCreatePinnedToCore(SpkTaskCode, "SpkTask", 4096, NULL, 1, NULL, 1);
xTaskCreatePinnedToCore(MicTaskCode, "MicTask", 4096, NULL, 1, NULL, 0);

}

// Speaker Task (Core 1)
void SpkTaskCode(void *pvParameters) {
Serial.println("Speaker Task Running...");

int sample_rate = 16000;
int frequency = 400; // 400 Hz tone
int num_samples = sample_rate / frequency;
int16_t pulse[num_samples];

// Generate square wave for 400 Hz tone
for (int i = 0; i < num_samples; i++) {
    pulse[i] = (i < num_samples / 2) ? 30000 : -30000; // 16-bit amplitude
}

size_t bytes_written;
for (;;) {
    i2s_channel_write(tx_handle, pulse, sizeof(pulse), &bytes_written, portMAX_DELAY);
    delay(10);
}

}

// Microphone Task (Core 0)
void MicTaskCode(void *pvParameters) {
Serial.println("Microphone Task Running...");

int32_t raw_data[128];  // 
int16_t processed_data[128]; // 
size_t bytes_read;

for (;;) {
    esp_err_t err = i2s_channel_read(rx_handle, raw_data, sizeof(raw_data), &bytes_read, portMAX_DELAY);
    if (err == ESP_OK && bytes_read > 0) {
        // 🔹 Extract the left-channel data properly
        for (int i = 0; i < bytes_read / sizeof(int32_t); i++) {
            processed_data[i] = (raw_data[i] >> 14) & 0xFFFF; 
        }

        Serial.println(processed_data[0]); 
    } else {
        Serial.println("Mic Read Error!");
    }
    delay(10);
}

}

void loop() {
} Not used - everything runs in FreeRTOS tasks
-- if anybody would be able to help or point me in the right direction that would be amazing

[pschatzmann]

I suggest that you dump what you have and just use my API: please read the Wiki of this project first!
Here is the example sketch that just copies the i2s input to the i2s output.

[ana7233]

Thank you