PDM Mic streaming with ESP32 Pico

[itisishan]

In similar vein to #203, I am trying to get a single Knowles V2S PDM mic working with this library. I am using the Adafruit QT Py ESP32 Pico with clk hooked up to GPIO 14 and data hooked up to GPIO 32. (Pinout: https://github.com/adafruit/Adafruit-QT-Py-ESP32-Pico-PCB/blob/main/Adafruit%20QT%20Py%20ESP32-Pico%20Pinout.pdf). I am using Arduino 2.0.4 on Mac.

Eventually I want to move to the web server sink, but for simplicity I've started by modifying "streams-i2s-serial.ino" example similar to rmick's configuration at the linked discussion:

/**
 * @file streams-i2s-serial.ino
 * @author Phil Schatzmann
 * @brief see https://github.com/pschatzmann/arduino-audio-tools/blob/main/examples/examples-stream/streams-i2s-serial/README.md
 * 
 * @author Phil Schatzmann
 * @copyright GPLv3
 */


#include "AudioTools.h"

int channels = 1;
I2SStream i2sStream; // Access I2S as stream
CsvOutput<int32_t> csvStream(Serial, channels);
StreamCopy copier(csvStream, i2sStream); // copy i2sStream to csvStream

// Arduino Setup
void setup(void) {
    Serial.begin(115200);
    AudioLogger::instance().begin(Serial, AudioLogger::Info);
    

    auto cfg = i2sStream.defaultConfig(RX_MODE);
    cfg.signal_type = PDM;
    cfg.i2s_format = I2S_STD_FORMAT;
    cfg.sample_rate = 22050;
    cfg.channels = 1;
    cfg.bits_per_sample = 16;
    cfg.pin_bck = 14;
    cfg.pin_data = 32;
    cfg.pin_ws = 4;

    // auto cfg = i2sStream.defaultConfig(RX_MODE);
    // cfg.i2s_format = I2S_STD_FORMAT; // or try with I2S_LSB_FORMAT
    // cfg.bits_per_sample = 32;
    // cfg.channels = channels;
    // cfg.sample_rate = 44100;
    // cfg.is_master = true;
    //  // this module nees a master clock if the ESP32 is master
    // cfg.use_apll = false;  // try with yes
    // cfg.pin_mck = 3; 
    i2sStream.begin(cfg);

    // make sure that we have the correct channels set up
    csvStream.begin(cfg);

}

// Arduino loop - copy data
void loop() {
    copier.copy();
}

Once uploaded, I get this repeated message on the serial output.

ELF file SHA256: 3308bd5e7ad2349e

Rebooting...
ets Jul 29 2019 12:21:46

rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 271414342, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0030,len:1184
load:0x40078000,len:13220
ho 0 tail 12 room 4
load:0x40080400,len:3028
entry 0x400805e4
Guru Meditation Error: Core  1 panic'ed (LoadProhibited). Exception was unhandled.

Core  1 register dump:
PC      : 0x400d6fd0  PS      : 0x00060830  A0      : 0x800d2d06  A1      : 0x3ffb2190  
A2      : 0x00000000  A3      : 0x3ffb9d0c  A4      : 0x00000400  A5      : 0x3ffb21dc  
A6      : 0xffffffff  A7      : 0x3ffc274c  A8      : 0x00000000  A9      : 0x80000000  
A10     : 0x00000001  A11     : 0x00000001  A12     : 0x80000020  A13     : 0x00000007  
A14     : 0x00000005  A15     : 0x00000001  SAR     : 0x00000003  EXCCAUSE: 0x0000001c  
EXCVADDR: 0x0000001c  LBEG    : 0x400873de  LEND    : 0x400873e9  LCOUNT  : 0x00000000  


Backtrace: 0x400d6fcd:0x3ffb2190 0x400d2d03:0x3ffb21d0 0x400d2e80:0x3ffb2210 0x400d34ff:0x3ffb2230 0x400d3606:0x3ffb2270 0x400d4cc1:0x3ffb2290

Other examples, like "streams_adc_serial.ino" work without issue.

Any guidance appreciated! Thanks!

[pschatzmann]

It seems that you did not read https://github.com/pschatzmann/arduino-audio-tools/wiki/It's-not-working

[itisishan]

Cool, thanks, I'll take a look at the trace decoders!

[pschatzmann]

I never used PDM, so I don't know if this is working or not. In any case you could try to read the data via regular I2S and apply a low pass filter to get an analog PCM result

[pschatzmann]

I updated the documentation: https://github.com/pschatzmann/arduino-audio-tools/wiki/External-ADC