i2s_read with external I2S microphone always returns zero (IDFGH-1805)

[morganrallen]

I've spent weeks trying dozens of variation but cannot seem to get i2s_read to return anything but zeros when reading from ICS-43434. My code is very similar to an ESP32 Arduino 1.0.2 example that works, and even if I use i2s_read_bytes to match it even more closely I cannot get it to work, which has me wondering if newer versions of the IDF have a bug related to external I2S inputs.

Environment

• Development Kit: https://www.tindie.com/products/microwavemont/esp32-simple-alexa/
• Module or chip used: ESP32-WROVER
• IDF version: v4.0-dev-1443-g39f090a4f
• Build System: CMake
• Compiler version: 1.22.0-80-g6c4433a
• Operating System: Linux
• Power Supply: USB

Problem Description

i2s initialization goes as expected but when i2s_read, or i2s_read_bytes are called, they always return zero.

Expected Behavior

Get non-zero response

Actual Behavior

Zeros

My test case that does not work against the IDF listed above.
https://gitlab.com/morganrallen/i2s-test-case
Although this code when compiled against Arduino ESP32 1.0.2 works as expected.
https://github.com/maspetsberger/esp32-i2s-mems/blob/master/examples/VUMeterDemo/VUMeterDemo.ino

[Alvin1Zhang]

@morganrallen Thanks for reporting the issue, we will look into it.

[amirgon]

I see the same problem.

[koobest]

Hi, @morganrallen
If the DIN pin is connected to vcc, is the read data still 0?

thanks !!

[leleb]

Me too having this issue after rebuilding an old working project.
for the moment I solved rolling back to espressif platform version 1.9.0.
In platform.ini set:
platform = espressif32@1.9.0
using later platforms (1.10.0 or 1.11.0 or latest 1.11.1) makes my I2S microphone not working.

[leleb]

Solved: using latest platform must swap left and right channel in configuration structure
i2s_config_t i2s_config = {
...
.channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
...

while in older platform works using I2S_CHANNEL_FMT_ONLY_RIGHT

[miketeachman]

Not sure why this was closed as it is a bug that was fixed in other versions. I'll re-open the issue to see if the Espressif team will fix it in v4.0.2

[Younes-SadatNejad]

Yes I am experiencing the same problem when trying to read I2S MEMS Microphone data,.
Changing the channel does not solve the problem
Would you kindly provide an update @Alvin1Zhang

[ginkgm]

Hi @miketeachman @Younes-SadatNejad ,

Have you tried @leleb 's solution above? And could you please provide the IDF version you are using, and maybe a simple piece of code to reproduce the issue? If you are working on the Arduino, please also provide details for that. It will help us locate the issue more quickly.

[miketeachman]

Hi @ginkgm,

For me, changing to I2S_CHANNEL_FMT_ONLY_RIGHT is a workaround to this bug. I submitted a new issue on the bug.
#6625. This is not a new bug. It is an older bug that has reappeared in at least one version of ESP-IDF. I am using v4.0.2.

I discovered this bug while writing an I2S driver for MicroPython. I was able to add two lines of low-level C code to fix the problem:
https://github.com/miketeachman/micropython/blob/i2s/ports/esp32/machine_i2s.c#L550

// apply workaround for bug in some ESP-IDF versions that swap
// the left and right channels
// https://github.com/espressif/esp-idf/issues/6625
REG_SET_BIT(I2S_CONF_REG(self->i2s_id), I2S_TX_MSB_RIGHT);
REG_SET_BIT(I2S_CONF_REG(self->i2s_id), I2S_RX_MSB_RIGHT);

[Younes-SadatNejad]

Hello @ginkgm ,
Thank you so much for getting back to me.
I am using v4.4-dev-4-g73db14240 for IDF version
Here is my code, I am trying to read the samples of MEMS microphone. Using LEFT or RIGHT channel does not change the result, I am getting all zero. While a similar code in Arduino with I2S_pip_sample is working fine.
Commenting the sample shift results in getting random values that does not change by triggering of microphone ...

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "esp_system.h"
#include "esp_log.h"
#include "nvs_flash.h"
#include "freertos/queue.h"
#include "driver/i2s.h"
#include "driver/gpio.h"

#define TAG "I2teSt"
#define I2S_SAMPLE_RATE (44100)
#define I2S_NUM (I2S_NUM_0)
#define I2S_READ_LEN (1 << 7)

static char* i2s_read_buff;

int32_t sample=0;
void i2s_init() {
esp_err_t err;

const i2s_config_t i2s_config = {
.mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX),
.sample_rate = I2S_SAMPLE_RATE,
.bits_per_sample = I2S_BITS_PER_SAMPLE_32BIT,
.channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
.communication_format = I2S_COMM_FORMAT_STAND_I2S,//(i2s_comm_format_t)(I2S_COMM_FORMAT_I2S | I2S_COMM_FORMAT_I2S_MSB),
.intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
.dma_buf_count = 8,
.dma_buf_len = I2S_READ_LEN
};

const i2s_pin_config_t pin_config = {
.bck_io_num = 14,
.ws_io_num = 15,
.data_out_num = -1,
.data_in_num = 32
};

err = i2s_driver_install(I2S_NUM, &i2s_config, 0, NULL);
if (err != ESP_OK) {
ESP_LOGI(TAG, "Failed installing driver: %d\n", err);
while (true);
}
err = i2s_set_pin(I2S_NUM, &pin_config);
if (err != ESP_OK) {
ESP_LOGI(TAG, "Failed setting pin: %d\n", err);
while (true);
}
ESP_LOGI(TAG, "I2S driver installed.");
}

void app_main() {
i2s_init();

size_t bytes_read;

i2s_read_buff = (char*) calloc(I2S_READ_LEN, sizeof(char));

i2s_start(I2S_NUM);

while(1) {
ESP_ERROR_CHECK(i2s_read(I2S_NUM, (void*) i2s_read_buff, I2S_READ_LEN, &bytes_read, portMAX_DELAY));

for(int i = 0; i < bytes_read; i++) {
  // all 0 output
 	sample = (int32_t)i2s_read_buff[i];
	sample = ~(sample>>14)+1;
	printf("%d\n",(int16_t)sample);
}

}
};

[FedericoBusero]

Is this issue fixed? I still experience this issue on ESP32-S2 (lolin S2 mini) in Arduino esp32 board version 2.09 (based on IDF 4.4.4), Microphone INMP441. I have to set
channel_format = I2S_CHANNEL_FMT_ONLY_RIGHT
independant of the wiring of the L/R pin of the microphone.