esp-idf: I2S mic not working since 4.4 (IDFGH-8138)

The bug was found, the rx_chan_mod on v4.4 is set to opposite value comparing to v5.0 and v5.1

Details

Concretely, the rx_chan_mod is actually related to msdb_right bit, meanwhile msdb_right is depended on the bits_per_sample. The correct relations are (ESP32 mono mode specific):

┌──────────────────┬─────────────┬───────────────┬──────────────────┐
│ bits_per_sample  │  msb_right  │  rx_chan_mod  │  sample_channel  │
├──────────────────┼─────────────┼───────────────┼──────────────────┤
│       16         │      1      │       1       │    only_right    │
├──────────────────┼─────────────┼───────────────┼──────────────────┤
│       16         │      1      │       2       │    only_left     │
├──────────────────┼─────────────┼───────────────┼──────────────────┤
│       32         │      0      │       2       │    only_right    │
├──────────────────┼─────────────┼───────────────┼──────────────────┤
│       32         │      0      │       1       │    only_left     │
└──────────────────┴─────────────┴───────────────┴──────────────────┘

The bug is that rx_chan_mod on v4.4 didn’t take msb_right into consideration, so that the left channel and the right channel are exchanged.

Solution

The bug will be fixed in the next minor version, for now, you can try the following way to get a temporary fix.

Workaround

• You can set to the opposite channel when using 32 bit-width data.

• Or, force to update the register after i2s install:

  #include "hal/i2s_hal.h"
  // ...
  i2s_driver_install();
  // ...
  i2s_ll_rx_set_chan_mod(&I2S0, 1);  // 32-bit only left
  

Fix patch

You can also try the patch:

0001-i2s-fixed-incorrect-channel-format-on-ESP32.patch

@L-KAYA Are there any updates on this? As stated the workaround is rather simple but it would be ideal to have this fixed. Anything else we can test?

It’s indeed a bug before, that only_left is actually only_right meanwhile only_right is still only_right, but it has been fixed on release/4.4 about 3 weeks ago.

Have you checked which channel your mic actually sampling (i.e. left when L/R pin of INMP441 is pulled down and right when it is pulled up)?

Thanks for raising this, I am having the same issue - also with Tasmota image: It seems to have stopped between 4.4.0 and 4.4.3

Working: platform = https://github.com/tasmota/platform-espressif32/releases/download/v2.0.2.3/platform-espressif32-2.0.2.3.zip framework-espidf @ 3.40400.0 (4.4.0)

Not workingt: platform = https://github.com/tasmota/platform-espressif32 framework-espidf @ 3.40403.0 (4.4.3)

I am using the following I2S Config: ` i2s_config_t i2s_config_micro = { .mode = (i2s_mode_t) (I2S_MODE_MASTER | I2S_MODE_RX), .sample_rate = 16000,

        //  The data word size is set at 32 bits and "I2S_PHILIPS_MODE" format. So a single stereo frame consists of two 32-bit PCM words or 8 bytes.
        //  The actual PCM audio data is 24 bits wide, is signed and is stored in little-endian format with 8 bits of left-justified 0 "padding".
        .bits_per_sample = I2S_BITS_PER_SAMPLE_32BIT,

        .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT, // was I2S_CHANNEL_FMT_RIGHT_LEFT
        .communication_format = i2s_comm_format_t(I2S_COMM_FORMAT_I2S),
        .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
        .dma_buf_count = 4,
        .dma_buf_len = 1024,
        .use_apll = false,
        .tx_desc_auto_clear = false,
        .fixed_mclk = 0
};`