decoding data sent from an esp32 using esp-idf over serial in nodejs

Question

I have an esp32 board loaded with this software which is logging values about the number of detected wifi and bluetooth devices detected via LoraWAN. In senddata.cpp it seems to be logging out the values that I need (though I'm not quite sure I understand how or where it is sending them via serial):

ESP_LOGD(TAG, "Sending count results: pax=%d / wifi=%d / ble=%d", count.pax, count.wifi_count, count.ble_count);

I set up a node.js app with the SerialPort.io library to be able to read data coming over serial. I've successfully identified the COM port on my PC that is receiving data, and I can log out the data buffer as follows:

const SerialPort = require("serialport").SerialPort;

const serialPort = new SerialPort({
  path: "COM4",
  baudRate: 9600,
  autoOpen: false,
});

serialPort.open(function (error) {
  if (error) {
    console.log("failed to open: " + error);
  } else {
    console.log("serial port opened");

    serialPort.on("data", function (data) {
      // get buffered data and parse it to an utf-8 string
      console.log(data);
      data = data.toString("utf-8");
      console.log(data);
    });

    serialPort.on("error", function (data) {
      console.log("Error: " + data);
    });
  }
});

Which yields output in node.js as a buffer, e.g. <Buffer bc 08 AD> and, after the toString("utf-8") as a bunch of gibberish. Clearly I am not encoding or decoding the serial output properly, but I'm not sure where to make adjustments. Does anyone know how I can get this serial output into the proper format to use in node.js?

--- Update Re: Questions ---

The board is a ttgo / lilygo lora32 - the library I used seems to say it supports both this board and communication over SPI. I am able to get readable data via the debug console in platform.io extension for vscode on windws / mac. I believe the baud is 9600, which was the only thing I seemed to need to specify on the serialports.io side.

I did receive this advice from the library author:

You need

1. a messagebuffer, to store the payload
2. a queue, as buffer for the serial data
3. a protocol, suitable for your application

1+2: see spislave.cpp (change the SPI transmit calls by serial port calls) 3: consider overhead and checksum, e.g. transfer the payload as byte array or UTF8 string, e.g. comma separated string with checksum, as used in NMEA.

Unfortunately I'm a bit out of my depth to make sense of that (though I'm working on it).

Also - the javascript code that has successfully worked via the things network uses to decode the payload from the board is here.

Answer 1

The problem may be related to this issue. This is how I got it working.

const port = new SerialPort({
  path: "COM4", baudRate: 115200,
  databits: 8,
  parity: false,
  stopbits: 1
});
port.on("open", function () {
  port.set({
    dtr: true,
    rts: true
  });

    // Read data from the port and parse as JSON
  port.on('data', (data) => {
    console.log('Data', data.toString('utf8'));
  });
});