Refactor DS18B20 Temperature Conversion Time Handling

[echavet]

Currently, the DS18B20 driver uses a fixed delay of 1 millisecond (board.io.sendOneWireDelay(pin, 1);) after requesting each sensor to perform a temperature conversion. However, the DS18B20 datasheet specifies that a conversion actually takes up to 750 milliseconds.

This misalignment could potentially lead to inaccuracies when reading from multiple DS18B20 sensors simultaneously, particularly if the requested frequency (options.freq) is shorter than the time required for a temperature conversion. Additionally, it's important to note that the implementation of the delayTask function on the Firmata side is not fully functional and relies on the inclusion of a "FirmataScheduler" module, which merely adds processor cycles and does not provide a true delay mechanism.

I propose refactoring the DS18B20 driver code as follows:

readThermometer = () => {
  let devicesToRead;
  let result;

  if (this.addresses) {
    devicesToRead = this.devices.filter(function (device) {
      const address = getAddress(device);
      return this.addresses.includes(address);
    }, this);
  } else {
    devicesToRead = [this.devices[0]];
  }

  devicesToRead.forEach(device => {
    board.io.sendOneWireReset(pin);
    board.io.sendOneWireWrite(pin, device, CONSTANTS.CONVERT_TEMPERATURE_COMMAND);
  });

  // Removed the following line, which appears to be unnecessary
  // board.io.sendOneWireDelay(pin, 1);

  let conversionTime = 750;  // Time needed for temperature conversion according to the DS18B20 datasheet

  readOne = () => {
    let device;

    if (devicesToRead.length === 0) {
      setTimeout(readThermometer, Math.max(0, freq - conversionTime));  // adjust delay to achieve desired freq
      return;
    }

    device = devicesToRead.pop();
    // read from the scratchpad
    board.io.sendOneWireReset(pin);

    board.io.sendOneWireWriteAndRead(pin, device, CONSTANTS.READ_SCRATCHPAD_COMMAND, CONSTANTS.READ_COUNT, (err, data) => {
      if (err) {
        this.emit("error", err);
        return;
      }

      result = (data[1] << 8) | data[0];
      this.emit("data", getAddress(device), result);

      readOne();
    });
  };

  setTimeout(readOne, conversionTime);  // changed the timing to accommodate the actual conversion time
};

With these changes, the DS18B20 driver seems (but should I need review) to correctly handle temperature conversion times, potentially improving the accuracy and reliability when reading from multiple DS18B20 sensors.

Could you review these changes and confirm that they correctly address the issue?