Windows 10 IoT Core image capture

Initiating image capture in response to a trigger was the next step, my plan is to use a button, or a proximity sensor like the passive infrared (PIR) module in the second image to trigger a photo.

Simple mechanical button trigger
PIR Sensor trigger

For my test rig (in addition to a RaspberryPI & generic USB Web camera) I’m using some Seeedstudio gear

The first step was to write an interrupt handler for the digital input, I figured triggering on the button push rather than release would make device more responsive.

/*
    Copyright ® 2019 Feb devMobile Software, All Rights Reserved
 
    MIT License
...
*/
namespace devMobile.Windows10IotCore.IoT.DigitalInputTrigger
{
	using System;
	using System.Diagnostics;
	using Windows.ApplicationModel.Background;
	using Windows.Devices.Gpio;

	public sealed class StartupTask : IBackgroundTask
	{
		private BackgroundTaskDeferral backgroundTaskDeferral = null;
		private GpioPin InterruptGpioPin = null;
		private const int InterruptPinNumber = 5;

		public void Run(IBackgroundTaskInstance taskInstance)
		{
			Debug.WriteLine("Application startup");

			try
			{
				GpioController gpioController = GpioController.GetDefault();

				InterruptGpioPin = gpioController.OpenPin(InterruptPinNumber);
				InterruptGpioPin.SetDriveMode(GpioPinDriveMode.InputPullUp);
				InterruptGpioPin.ValueChanged += InterruptGpioPin_ValueChanged;

				Debug.WriteLine("Digital Input Interrupt configuration success");
			}
			catch (Exception ex)
			{
				Debug.WriteLine($"Digital Input Interrupt configuration failed " + ex.Message);
				return;
			}

			//enable task to continue running in background
			backgroundTaskDeferral = taskInstance.GetDeferral();
		}

		private void InterruptGpioPin_ValueChanged(GpioPin sender, GpioPinValueChangedEventArgs args)
		{
			Debug.WriteLine($"{DateTime.UtcNow.ToLongTimeString()} Digital Input Interrupt {sender.PinNumber} triggered {args.Edge}");
		}
	}
}

Then I added in the camera functionality and made the interrupt handler async and await the camera and file system calls.

/*
    Copyright ® 2019 Feb devMobile Software, All Rights Reserved
 
    MIT License
...
*/
namespace devMobile.Windows10IotCore.IoT.PhotoDigitalInputTrigger
{
	using System;
	using System.Diagnostics;
	using Windows.ApplicationModel.Background;
	using Windows.Devices.Gpio;
	using Windows.Foundation.Diagnostics;
	using Windows.Media.Capture;
	using Windows.Media.MediaProperties;
	using Windows.Storage;

	public sealed class StartupTask : IBackgroundTask
	{
		private readonly LoggingChannel logging = new LoggingChannel("devMobile Photo Digital Input Trigger demo", null, new Guid("4bd2826e-54a1-4ba9-bf63-92b73ea1ac4a"));
		private BackgroundTaskDeferral backgroundTaskDeferral = null;
		private GpioPin InterruptGpioPin = null;
		private const int InterruptPinNumber = 5;
		private MediaCapture mediaCapture;
		private const string ImageFilenameFormat = "Image{0:yyMMddhhmmss}.jpg";
		private volatile bool CameraBusy = false;

		public void Run(IBackgroundTaskInstance taskInstance)
		{
			LoggingFields startupInformation = new LoggingFields();

			this.logging.LogEvent("Application starting");

			try
			{
				mediaCapture = new MediaCapture();
				mediaCapture.InitializeAsync().AsTask().Wait();
				Debug.WriteLine("Camera configuration success");

				GpioController gpioController = GpioController.GetDefault();

				InterruptGpioPin = gpioController.OpenPin(InterruptPinNumber);
				InterruptGpioPin.SetDriveMode(GpioPinDriveMode.InputPullUp);
				InterruptGpioPin.ValueChanged += InterruptGpioPin_ValueChanged;
				Debug.WriteLine("Digital Input Interrupt configuration success");
			}
			catch (Exception ex)
			{
				this.logging.LogMessage("Camera or digital input configuration failed " + ex.Message, LoggingLevel.Error);
				return;
			}

			startupInformation.AddString("PrimaryUse", mediaCapture.VideoDeviceController.PrimaryUse.ToString());
			startupInformation.AddInt32("Interrupt pin", InterruptPinNumber);

			this.logging.LogEvent("Application started", startupInformation);

			//enable task to continue running in background
			backgroundTaskDeferral = taskInstance.GetDeferral();
		}

		private async void InterruptGpioPin_ValueChanged(GpioPin sender, GpioPinValueChangedEventArgs args)
		{
			DateTime currentTime = DateTime.UtcNow;
			Debug.WriteLine($"{DateTime.UtcNow.ToLongTimeString()} Digital Input Interrupt {sender.PinNumber} triggered {args.Edge}");

			if (args.Edge == GpioPinEdge.RisingEdge)
			{
				return;
			}

			// Just incase - stop code being called while photo already in progress
			if (CameraBusy)
			{
				return;
			}
			CameraBusy = true;

			try
			{
				string filename = string.Format(ImageFilenameFormat, currentTime);

				IStorageFile photoFile = await KnownFolders.PicturesLibrary.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);
				ImageEncodingProperties imageProperties = ImageEncodingProperties.CreateJpeg();
				await mediaCapture.CapturePhotoToStorageFileAsync(imageProperties, photoFile);

				LoggingFields imageInformation = new LoggingFields();

				imageInformation.AddDateTime("TakenAtUTC", currentTime);
				imageInformation.AddString("Filename", filename);
				imageInformation.AddString("Path", photoFile.Path);

				this.logging.LogEvent("Captured image saved to storage", imageInformation);
			}
			catch (Exception ex)
			{
				this.logging.LogMessage("Camera photo or save failed " + ex.Message, LoggingLevel.Error);
			}
			CameraBusy = false;
		}
	}
}

I found that contactor bounce was an issue (Grove- Touch Sensor OK) with larger mechanical buttons so I added the CameraBusy boolean flag to try and prevent re-entrancy problems. I’ll trial some other types of proximity and beam based on real-world student projects.

ETW logging or PIR triggered image capture

The code is available on GitHub and is a bit of a work in progress.

Carbon Dioxide Sensor(MH-Z16) library comparison

The first library I looked at was for the DFRobot Gravity: UART Infrared CO2 Sensor (0-50000ppm). There was sample code provided on the associated wiki page. The code worked first time I ran it but I didn’t use this library due to the lack of checksum & packet header/footer validation.

/***************************************************
* Infrared CO2 Sensor 0-50000ppm(Wide Range)
* ****************************************************
* The follow example is used to detect CO2 concentration.
  
* @author lg.gang(lg.gang@qq.com)
* @version  V1.0
* @date  2016-6-6
  
* GNU Lesser General Public License.
* See <http://www.gnu.org/licenses/> for details.
* All above must be included in any redistribution
* ****************************************************/ 
#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 11); // RX, TX
unsigned char hexdata[9] = {0xFF,0x01,0x86,0x00,0x00,0x00,0x00,0x00,0x79}; //Read the gas density command /Don't change the order
void setup() {
  
  Serial.begin(9600);
  while (!Serial) {

  }
  mySerial.begin(9600);

}

void loop() {
   mySerial.write(hexdata,9);
   delay(500);

 for(int i=0,j=0;i<9;i++)
 {
  if (mySerial.available()>0)
  {
     long hi,lo,CO2;
     int ch=mySerial.read();

    if(i==2){     hi=ch;   }   //High concentration
    if(i==3){     lo=ch;   }   //Low concentration
    if(i==8) {
               CO2=hi*256+lo;  //CO2 concentration
      Serial.print("CO2 concentration: ");
      Serial.print(CO2);
      Serial.println("ppm");      
      }
    }   
  } 
}

After some GitHub searching the second library I looked at was abbozza_CO2_MHZ16_arduino by Michael Brinkmeier. This library appears to be “plug-in” module for the abbozza! framework. I didn’t use this library due to the lack of checksum & packet header/footer validation.

/**
 * @license
 * abbozza! Calliope plugin for the MH-Z16 CO2 sensor
 * 
 * The sensor has to be connected to a serial connection with 9600 baud.
 *
 * Copyright 2015 Michael Brinkmeier ( michael.brinkmeier@uni-osnabrueck.de )
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "SoftwareSerial.h"
#include "MHZ16.h"
#include "Arduino.h"

MHZ16::MHZ16(int tx, int rx) {
    this->serial = new SoftwareSerial(rx,tx,false);
    this->serial->begin(9600);
}


void MHZ16::calibrate() {
    int idx;
    for (idx = 0; idx < 9; idx++) {
        serial->write(cal[idx]);
    }
    delay(10);
}

void MHZ16::doMeasurement() {
    int idx;
    int bu;

    for (idx = 0; idx < 9; idx++) {
        serial->write(cmd[idx]);
    }
    delay(10);

    while (serial->available()) {
        do {
            bu = serial->read();
        } while (bu != 255);
        buf[0] = bu;

        idx = 1;
        while (serial->available() && (idx < 9)) {
            bu = serial->read();
            buf[idx] = bu;
            idx++;
        }

        if (idx == 9) {
            PPM = ((int) buf[2]) *256 + ((int) buf[3]);
        }
    }
}

int MHZ16::getPPM() {
    return PPM;
}

The third library was produced by Sandbox electronics for their selection of 10,000PPM thru 100,000PPM MH-Z16 sensors. Their datasheet looked similar(maybe newer?) to the Seeedstudio one and the packet format was the same.

Their library had checksum & packet header/footer validation but I didn’t use it because the carbon dioxide concentration was calculated using 4 bytes (maybe this was to support the different range sensors?)

/*
Description:
This is a example code for Sandbox Electronics NDIR CO2 sensor module.
You can get one of those products on
http://sandboxelectronics.com

Version:
V1.2

Release Date:
2019-01-10

Author:
Tiequan Shao          support@sandboxelectronics.com

Lisence:
CC BY-NC-SA 3.0

Please keep the above information when you use this code in your project.
*/

#include <SoftwareSerial.h>
#include <NDIR_SoftwareSerial.h>
#define  RECEIVE_TIMEOUT  (100)

#if ARDUINO >= 100
    #include "Arduino.h"
#else
    #include "WProgram.h"
#endif

class SoftwareSerial;

uint8_t NDIR_SoftwareSerial::cmd_measure[9]                = {0xFF,0x01,0x9C,0x00,0x00,0x00,0x00,0x00,0x63};
uint8_t NDIR_SoftwareSerial::cmd_calibrateZero[9]          = {0xFF,0x01,0x87,0x00,0x00,0x00,0x00,0x00,0x78};
uint8_t NDIR_SoftwareSerial::cmd_enableAutoCalibration[9]  = {0xFF,0x01,0x79,0xA0,0x00,0x00,0x00,0x00,0xE6};
uint8_t NDIR_SoftwareSerial::cmd_disableAutoCalibration[9] = {0xFF,0x01,0x79,0x00,0x00,0x00,0x00,0x00,0x86};

NDIR_SoftwareSerial::NDIR_SoftwareSerial(uint8_t rx_pin, uint8_t tx_pin) : serial(rx_pin, tx_pin, false)
{
}


uint8_t NDIR_SoftwareSerial::begin()
{
    serial.begin(9600);

    if (measure()) {
        return true;
    } else {
        return false;
    }
}

uint8_t NDIR_SoftwareSerial::measure()
{
    uint8_t i;
    uint8_t buf[9];
    uint32_t start = millis();

    serial.flush();

    for (i=0; i<9; i++) {
        serial.write(cmd_measure[i]);
    }

    for (i=0; i<9;) {
        if (serial.available()) {
            buf[i++] = serial.read();
        }

        if (millis() - start > RECEIVE_TIMEOUT) {
            return false;
        }
    }

    if (parse(buf)) {
        return true;
    }

    return false;
}


void NDIR_SoftwareSerial::calibrateZero()
{
    uint8_t i;

    for (i=0; i<9; i++) {
        serial.write(cmd_calibrateZero[i]);
    }
}


void NDIR_SoftwareSerial::enableAutoCalibration()
{
    uint8_t i;

    for (i=0; i<9; i++) {
        serial.write(cmd_enableAutoCalibration[i]);
    }
}


void NDIR_SoftwareSerial::disableAutoCalibration()
{
    uint8_t i;

    for (i=0; i<9; i++) {
        serial.write(cmd_disableAutoCalibration[i]);
    }
}


uint8_t NDIR_SoftwareSerial::parse(uint8_t *pbuf)
{
    uint8_t i;
    uint8_t checksum = 0;

    for (i=0; i<9; i++) {
        checksum += pbuf[i];
    }

    if (pbuf[0] == 0xFF && pbuf[1] == 0x9C && checksum == 0xFF) {
        ppm = (uint32_t)pbuf[2] << 24 | (uint32_t)pbuf[3] << 16 | (uint32_t)pbuf[4] << 8 | pbuf[5];
        return true;
    } else {
        return false;
    }
}

The forth library I looked at was MHZ-Z-C02-Sensors by Tobias Schürg this library was for different series of MHZ sensors. With re-synching, configurable timeouts and checksum validation it looked like the code could easily be adapted for the MH-Z16.

/* MHZ library

    By Tobias Schürg
*/

#include "MHZ.h"

const int MHZ14A = 14;
const int MHZ19B = 19;

const int MHZ14A_RESPONSE_TIME = 60;
const int MHZ19B_RESPONSE_TIME = 120;

const int STATUS_NO_RESPONSE = -2;
const int STATUS_CHECKSUM_MISMATCH = -3;
const int STATUS_INCOMPLETE = -4;
const int STATUS_NOT_READY = -5;

unsigned long lastRequest = 0;

MHZ::MHZ(uint8_t rxpin, uint8_t txpin, uint8_t pwmpin, uint8_t type)
    : co2Serial(rxpin, txpin) {
  _rxpin = rxpin;
  _txpin = txpin;
  _pwmpin = pwmpin;
  _type = type;

  co2Serial.begin(9600);
}

/**
 * Enables or disables the debug mode (more logging).
 */
void MHZ::setDebug(boolean enable) {
  debug = enable;
  if (debug) {
    Serial.println(F("MHZ: debug mode ENABLED"));
  } else {
    Serial.println(F("MHZ: debug mode DISABLED"));
  }
}

boolean MHZ::isPreHeating() {
  if (_type == MHZ14A) {
    return millis() < (3 * 60 * 1000);
  } else if (_type == MHZ19B) {
    return millis() < (3 * 60 * 1000);
  } else {
    Serial.println(F("MHZ::isPreHeating() => UNKNOWN SENSOR"));
    return false;
  }
}

boolean MHZ::isReady() {
  if (isPreHeating()) return false;
  if (_type == MHZ14A)
    return lastRequest < millis() - MHZ14A_RESPONSE_TIME;
  else if (_type == MHZ19B)
    return lastRequest < millis() - MHZ19B_RESPONSE_TIME;
  else {
    Serial.print(F("MHZ::isReady() => UNKNOWN SENSOR \""));
    Serial.print(_type);
    Serial.println(F("\""));
    return true;
  }
}

int MHZ::readCO2UART() {
  if (!isReady()) return STATUS_NOT_READY;
  if (debug) Serial.println(F("-- read CO2 uart ---"));
  byte cmd[9] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};
  byte response[9];  // for answer

  if (debug) Serial.print(F("  >> Sending CO2 request"));
  co2Serial.write(cmd, 9);  // request PPM CO2
  lastRequest = millis();

  // clear the buffer
  memset(response, 0, 9);

  int waited = 0;
  while (co2Serial.available() == 0) {
    if (debug) Serial.print(".");
    delay(100);  // wait a short moment to avoid false reading
    if (waited++ > 10) {
      if (debug) Serial.println(F("No response after 10 seconds"));
      co2Serial.flush();
      return STATUS_NO_RESPONSE;
    }
  }
  if (debug) Serial.println();

  // The serial stream can get out of sync. The response starts with 0xff, try
  // to resync.
  // TODO: I think this might be wrong any only happens during initialization?
  boolean skip = false;
  while (co2Serial.available() > 0 && (unsigned char)co2Serial.peek() != 0xFF) {
    if (!skip) {
      Serial.print(F("MHZ: - skipping unexpected readings:"));
      skip = true;
    }
    Serial.print(" ");
    Serial.print(co2Serial.peek(), HEX);
    co2Serial.read();
  }
  if (skip) Serial.println();

  if (co2Serial.available() > 0) {
    int count = co2Serial.readBytes(response, 9);
    if (count < 9) {
      co2Serial.flush();
      return STATUS_INCOMPLETE;
    }
  } else {
    co2Serial.flush();
    return STATUS_INCOMPLETE;
  }

  if (debug) {
    // print out the response in hexa
    Serial.print(F("  << "));
    for (int i = 0; i < 9; i++) {
      Serial.print(response[i], HEX);
      Serial.print(F("  "));
    }
    Serial.println(F(""));
  }

  // checksum
  byte check = getCheckSum(response);
  if (response[8] != check) {
    Serial.println(F("MHZ: Checksum not OK!"));
    Serial.print(F("MHZ: Received: "));
    Serial.println(response[8], HEX);
    Serial.print(F("MHZ: Should be: "));
    Serial.println(check, HEX);
    temperature = STATUS_CHECKSUM_MISMATCH;
    co2Serial.flush();
    return STATUS_CHECKSUM_MISMATCH;
  }

  int ppm_uart = 256 * (int)response[2] + response[3];

  temperature = response[4] - 44;  // - 40;

  byte status = response[5];
  if (debug) {
    Serial.print(F(" # PPM UART: "));
    Serial.println(ppm_uart);
    Serial.print(F(" # Temperature? "));
    Serial.println(temperature);
  }

  // Is always 0 for version 14a  and 19b
  // Version 19a?: status != 0x40
  if (debug && status != 0) {
    Serial.print(F(" ! Status maybe not OK ! "));
    Serial.println(status, HEX);
  } else if (debug) {
    Serial.print(F(" Status  OK: "));
    Serial.println(status, HEX);
  }

  co2Serial.flush();
  return ppm_uart;
}

uint8_t MHZ::getLastTemperature() {
  if (isPreHeating()) return STATUS_NOT_READY;
  return temperature;
}

byte MHZ::getCheckSum(byte* packet) {
  if (debug) Serial.println(F("  getCheckSum()"));
  byte i;
  unsigned char checksum = 0;
  for (i = 1; i < 8; i++) {
    checksum += packet[i];
  }
  checksum = 0xff - checksum;
  checksum += 1;
  return checksum;
}

int MHZ::readCO2PWM() {
  // if (!isReady()) return STATUS_NOT_READY; not needed?
  if (debug) Serial.print(F("-- reading CO2 from pwm "));
  unsigned long th, tl, ppm_pwm = 0;
  do {
    if (debug) Serial.print(".");
    th = pulseIn(_pwmpin, HIGH, 1004000) / 1000;
    tl = 1004 - th;
    ppm_pwm = 5000 * (th - 2) / (th + tl - 4);
  } while (th == 0);
  if (debug) {
    Serial.print(F("\n # PPM PWM: "));
    Serial.println(ppm_pwm);
  }
  return ppm_pwm;
}

The forth library I looked at was MHZ16_uart by Intar it had been updated recently, was quite lightweight, had timeouts, checksum & packet header/footer validation.

/*
  MHZ16_uart.cpp - MH-Z16 CO2 sensor library for ESP-32
  by Intar BV
  version 0.1
  
  License MIT
*/

#include "MHZ16_uart.h"
#include "Arduino.h"


#define WAIT_READ_TIMES	100
#define WAIT_READ_DELAY	10

// public

MHZ16_uart::MHZ16_uart(){
}
MHZ16_uart::MHZ16_uart(int rx, int tx){
	begin(rx,tx);
}

MHZ16_uart::~MHZ16_uart(){
}

#ifdef ARDUINO_ARCH_ESP32
void MHZ16_uart::begin(int rx, int tx, int s){
	_rx_pin = rx;
	_tx_pin = tx;
	_start_millis = millis();
	_serialno = s;
}
#else
void MHZ16_uart::begin(int rx, int tx){
	_rx_pin = rx;
	_start_millis = millis();
	_tx_pin = tx;
}
#endif

void MHZ16_uart::calibrateZero() {
	writeCommand( zerocalib );
}

void MHZ16_uart::calibrateSpan(int ppm) {
	if( ppm < 1000 )	return;

	uint8_t com[MHZ16_uart::REQUEST_CNT];
	for(int i=0; i<MHZ16_uart::REQUEST_CNT; i++) {
		com[i] = spancalib[i];
	}
	com[3] = (uint8_t)(ppm/256);
	com[4] = (uint8_t)(ppm%256);
	writeCommand( com );
}

int MHZ16_uart::getPPM() {
	return getSerialData();
}

boolean MHZ16_uart::isWarming(){
	return millis() <= _start_millis + PREHEAT_MS;
}

//protected
void MHZ16_uart::writeCommand(uint8_t cmd[]) {
	writeCommand(cmd,NULL);
}

void MHZ16_uart::writeCommand(uint8_t cmd[], uint8_t* response) {
#ifdef ARDUINO_ARCH_ESP32
	HardwareSerial hserial(_serialno);
	hserial.begin(9600, SERIAL_8N1, _rx_pin, _tx_pin);
#else
	SoftwareSerial hserial(_rx_pin, _tx_pin);
	hserial.begin(9600);
#endif
    hserial.write(cmd, REQUEST_CNT);
	hserial.write(MHZ16_checksum(cmd));
	hserial.flush();
	
	if (response != NULL) {
		int i = 0;
		while(hserial.available() <= 0) {
			if( ++i > WAIT_READ_TIMES ) {
				Serial.println("error: can't get MH-Z16 response.");
				return;
			}
			yield();
			delay(WAIT_READ_DELAY);
		}
		hserial.readBytes(response, MHZ16_uart::RESPONSE_CNT);
	}

}

//private

int MHZ16_uart::getSerialData() {
	uint8_t buf[MHZ16_uart::RESPONSE_CNT];
	for( int i=0; i<MHZ16_uart::RESPONSE_CNT; i++){
		buf[i]=0x0;
	}

	writeCommand(getppm, buf);
	int co2 = 0, co2temp = 0, co2status =  0;

	// parse
	if (buf[0] == 0xff && buf[1] == 0x86 && MHZ16_checksum(buf) == buf[MHZ16_uart::RESPONSE_CNT-1]) {
		co2 = buf[2] * 256 + buf[3];
	} else {
		co2 = co2temp = co2status = -1;
	}
	return co2;
}	

uint8_t MHZ16_uart::MHZ16_checksum( uint8_t com[] ) {
	uint8_t sum = 0x00;
	for ( int i = 1; i < MHZ16_uart::REQUEST_CNT; i++) {
		sum += com[i];
	}
	sum = 0xff - sum + 0x01;
	return sum;
}

It ran second time on one of my Arduino devices (after I figured out how to configure the serial port pins) and though intended for an ESP8266 device this is the library I will field test.

#include <MHZ16_uart.h>

//Select 2 digital pins as SoftwareSerial's Rx and Tx. For example, Rx=2 Tx=3
MHZ16_uart mySensor(4,5);

void setup()
{
  Serial.begin(9600);

  mySensor.begin(4,5); 
}


void loop() 
{
  if ( !mySensor.isWarming())
  {
    Serial.print("CO2 Concentration is ");
    Serial.print(mySensor.getPPM());
    Serial.println("ppm");
  }
  else
{
    Serial.println("isWarming");
  }
  
  delay(10000);
}

This was just a sample of the libraries I found on GitHub if I missed a good a library contact me via the comments.

Grove – Carbon Dioxide Sensor(MH-Z16) trial

In preparation for a student project to monitor the CO2 levels in a number of classrooms I purchased a Grove – Carbon Dioxide Sensor(MH-Z16) for evaluation.


Arduino Uno R3 and CO2 Sensor

I downloaded the seeedstudio wiki example code, compiled and uploaded it to one of my Arduino Uno R3 devices.

I increased delay between readings to 10sec and reduced the baud rate of the serial logging to 9600baud.

/*
  This test code is write for Arduino AVR Series(UNO, Leonardo, Mega)
  If you want to use with LinkIt ONE, please connect the module to D0/1 and modify:

  // #include <SoftwareSerial.h>
  // SoftwareSerial s_serial(2, 3);      // TX, RX

  #define sensor Serial1
*/


#include <SoftwareSerial.h>
SoftwareSerial s_serial(2, 3);      // TX, RX

#define sensor s_serial

const unsigned char cmd_get_sensor[] =
{
    0xff, 0x01, 0x86, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x79
};

unsigned char dataRevice[9];
int temperature;
int CO2PPM;

void setup()
{
    sensor.begin(9600);
    Serial.begin(9600);
    Serial.println("get a 'g', begin to read from sensor!");
    Serial.println("********************************************************");
    Serial.println();
}

void loop()
{
    if(dataRecieve())
    {
        Serial.print("Temperature: ");
        Serial.print(temperature);
        Serial.print("  CO2: ");
        Serial.print(CO2PPM);
        Serial.println("");
    }
    delay(10000);
}

bool dataRecieve(void)
{
    byte data[9];
    int i = 0;

    //transmit command data
    for(i=0; i<sizeof(cmd_get_sensor); i++)
    {
        sensor.write(cmd_get_sensor[i]);
    }
    delay(10);
    //begin reveiceing data
    if(sensor.available())
    {
        while(sensor.available())
        {
            for(int i=0;i<9; i++)
            {
                data[i] = sensor.read();
            }
        }
    }

    for(int j=0; j<9; j++)
    {
        Serial.print(data[j]);
        Serial.print(" ");
    }
    Serial.println("");

    if((i != 9) || (1 + (0xFF ^ (byte)(data[1] + data[2] + data[3] + data[4] + data[5] + data[6] + data[7]))) != data[8])
    {
        return false;
    }

    CO2PPM = (int)data[2] * 256 + (int)data[3];
    temperature = (int)data[4] - 40;

    return true;
}

The debug output wasn’t too promising there weren’t any C02 parts per million (ppm) values and the response payloads looked wrong. So I downloaded the MH-Z16 NDIR CO2 Sensor datasheet for some background. The datasheet didn’t mention any temperature data in the message payloads so I removed that code.

The response payload validation code was all on one line and hard to figure out what it was doing.

    if((i != 9) || (1 + (0xFF ^ (byte)(data[1] + data[2] + data[3] + data[4] + data[5] + data[6] + data[7]))) != data[8])
    {
        return false;
    }

To make debugging easier I split the payload validation code into several steps so I could see what was failing.

/*
  This test code is write for Arduino AVR Series(UNO, Leonardo, Mega)
  If you want to use with LinkIt ONE, please connect the module to D0/1 and modify:

  // #include <SoftwareSerial.h>
  // SoftwareSerial s_serial(2, 3);      // TX, RX

  #define sensor Serial1
*/


#include <SoftwareSerial.h>
SoftwareSerial s_serial(2, 3);      // TX, RX

#define sensor s_serial

const unsigned char cmd_get_sensor[] =
{
    0xff, 0x01, 0x86, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x79
};

unsigned char dataRevice[9];
int CO2PPM;

void setup()
{
    sensor.begin(9600);
    Serial.begin(9600);
    Serial.println("get a 'g', begin to read from sensor!");
    Serial.println("********************************************************");
    Serial.println();
}

void loop()
{
    if(dataRecieve())
    {
        Serial.print("  CO2: ");
        Serial.print(CO2PPM);
        Serial.println("");
    }
    delay(10000);
}

bool dataRecieve(void)
{
    byte data[9];
    int i = 0;

    //transmit command data
    for(i=0; i<sizeof(cmd_get_sensor); i++)
    {
        sensor.write(cmd_get_sensor[i]);
    }
    delay(10);
    //begin reveiceing data
    if(sensor.available())
    {
        while(sensor.available())
        {
            for(int i=0;i<9; i++)
            {
                data[i] = sensor.read();
            }
        }
    }

    for(int j=0; j<9; j++)
    {
        Serial.print(data[j]);
        Serial.print(" ");
    }
    Serial.println("");

    // First calculate then validate the check sum as there is no point in proceeding if the packet is corrupted. (code inspired by datasheet algorithm)
    byte checksum = 0 ;
    for(int j=1; j<8; j++)
    {
      checksum += data[j];
    }
    checksum=0xff-checksum; 
    checksum+=1;
       
    if  (checksum != data[8])
    {
      Serial.println("Error checksum");
      return false;
    }

    // Then check the start byte to make sure response is what we were expecting
    if ( data[0] != 0xFF )
    {
        Serial.println("Error start byte");
        return false;
    }

    // Then check the command byte to make sure response is what we were expecting
    if ( data[1] != 0x86 )
    {
        Serial.println("Error command");
        return false;
    }


    CO2PPM = (int)data[2] * 256 + (int)data[3];

    return true;
}

From these modifications I could see the payload was messed up and based on the datasheet message descriptions it looked like it was offset by a byte or two.

15:58:32.509 -> get a 'g', begin to read from sensor!
15:58:32.578 -> ********************************************************
15:58:32.612 -> 
15:58:32.612 -> 255 134 6 238 76 0 0 1 255 
15:58:32.647 -> Error checksum
15:58:42.631 -> 57 255 134 6 246 76 0 0 1 
15:58:42.666 -> Error checksum
15:58:52.667 -> 49 255 134 5 125 76 0 0 1 
15:58:52.702 -> Error checksum
15:59:02.704 -> 171 255 134 4 86 76 0 0 1 
15:59:02.750 -> Error checksum

I had a look at the code and the delay(10) after sending the sensor reading request message caught my attention. I have found that often delay(x) commands are used to “tweak” the code to get it to work.

These “tweaks” often break when code is run on a different device or sensor firmware is updated changing the timing of individual bytes, or request-response processes.

I removed the delay(10) replaced it with a serial.flush() and changed the code to display the payload bytes in hexadecimal.

/*
  This test code is write for Arduino AVR Series(UNO, Leonardo, Mega)
  If you want to use with LinkIt ONE, please connect the module to D0/1 and modify:

  // #include <SoftwareSerial.h>
  // SoftwareSerial s_serial(2, 3);      // TX, RX

  #define sensor Serial1
*/


#include <SoftwareSerial.h>
SoftwareSerial s_serial(2, 3);      // TX, RX

#define sensor s_serial

const unsigned char cmd_get_sensor[] =
{
    0xff, 0x01, 0x86, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x79
};

unsigned char dataRevice[9];
int CO2PPM;

void setup()
{
    sensor.begin(9600);
    Serial.begin(9600);
    Serial.println("get a 'g', begin to read from sensor!");
    Serial.println("********************************************************");
    Serial.println();
}

void loop()
{
    if(dataRecieve())
    {
        Serial.print("  CO2: ");
        Serial.print(CO2PPM);
        Serial.println("");
    }
    delay(10000);
}

bool dataRecieve(void)
{
    byte data[9];
    int i = 0;

    //transmit command data
    for(i=0; i<sizeof(cmd_get_sensor); i++)
    {
        sensor.write(cmd_get_sensor[i]);
    }
    Serial.flush();
    
    //begin reveiceing data
    if(sensor.available())
    {
        while(sensor.available())
        {
            for(int i=0;i<9; i++)
            {
                data[i] = sensor.read();
            }
        }
    }

    for(int j=0; j<9; j++)
    {
        Serial.print(data[j],HEX);
        Serial.print(" ");
    }
    Serial.println("");

    // First calculate then validate the check sum as there is no point in proceeding if the packet is corrupted. (code inspired by datasheet algorithm)
    byte checksum = 0 ;
    for(int j=1; j<8; j++)
    {
      checksum += data[j];
    }
    checksum=0xff-checksum; 
    checksum+=1;
       
    if  (checksum != data[8])
    {
      Serial.println("Error checksum");
      return false;
    }

    // Then check the start byte to make sure response is what we were expecting
    if ( data[0] != 0xFF )
    {
        Serial.println("Error start byte");
        return false;
    }

    // Then check the command byte to make sure response is what we were expecting
    if ( data[1] != 0x86 )
    {
        Serial.println("Error command");
        return false;
    }


    CO2PPM = (int)data[2] * 256 + (int)data[3];

    return true;
}

The initial values from the sensor were a bit high, but after leaving the device running for 3 minutes (Preheat time in the documentation) they settled down into a reasonable range

16:14:31.686 -> get a 'g', begin to read from sensor!
16:14:31.721 -> ********************************************************
16:14:31.789 -> 
16:14:31.789 -> 255 134 6 224 75 0 0 1 72 
16:14:31.823 ->   CO2: 1760
16:14:41.824 -> 255 134 6 224 75 0 0 1 72 
16:14:41.824 ->   CO2: 1760
16:14:51.824 -> 255 134 5 189 75 0 0 1 108 
16:14:51.858 ->   CO2: 1469
16:15:01.868 -> 255 134 3 157 75 0 0 1 142 
16:15:01.868 ->   CO2: 925
16:15:11.857 -> 255 134 3 223 75 0 0 1 76 
16:15:11.892 ->   CO2: 991
16:15:21.882 -> 255 134 6 56 75 0 0 1 240 
16:15:21.917 ->   CO2: 1592
16:15:31.911 -> 255 134 4 186 75 0 0 1 112 
16:15:31.945 ->   CO2: 1210
16:15:41.927 -> 255 134 3 131 75 0 0 1 168 
16:15:41.962 ->   CO2: 899
16:15:51.940 -> 255 134 3 30 75 0 0 1 13 
16:15:51.975 ->   CO2: 798
16:16:01.986 -> 255 134 2 201 75 0 0 1 99 
16:16:01.986 ->   CO2: 713
16:16:11.985 -> 255 134 4 133 75 0 0 1 165 
16:16:12.019 ->   CO2: 1157
16:16:22.020 -> 255 134 6 62 75 0 0 1 234 
16:16:22.053 ->   CO2: 1598
16:16:32.041 -> 255 134 5 80 75 0 0 1 217 
16:16:32.041 ->   CO2: 1360
16:16:42.057 -> 255 134 3 204 75 0 0 1 95 
16:16:42.092 ->   CO2: 972
16:16:52.084 -> 255 134 3 191 75 0 0 1 108 
16:16:52.084 ->   CO2: 959
16:17:02.102 -> 255 134 2 230 75 0 0 1 70 
16:17:02.102 ->   CO2: 742
16:17:12.094 -> 255 134 3 106 75 0 0 1 193 
16:17:12.129 ->   CO2: 874
16:17:22.111 -> 255 134 2 227 75 0 0 1 73 
16:17:22.145 ->   CO2: 739
16:17:32.139 -> 255 134 3 225 75 0 0 1 74 
16:17:32.172 ->   CO2: 993
16:17:42.170 -> 255 134 3 109 75 0 0 1 190 
16:17:42.204 ->   CO2: 877
16:17:52.174 -> 255 134 2 188 75 0 0 1 112 
16:17:52.207 ->   CO2: 700
16:18:02.218 -> 255 134 2 70 75 0 0 1 230 
16:18:02.253 ->   CO2: 582
16:18:12.239 -> 255 134 2 163 75 0 0 1 137 
16:18:12.239 ->   CO2: 675
16:18:22.251 -> 255 134 2 110 75 0 0 1 190 
16:18:22.285 ->   CO2: 622
16:18:32.246 -> 255 134 2 83 75 0 0 1 217 
16:18:32.280 ->   CO2: 595
16:18:42.277 -> 255 134 2 48 75 0 0 1 252 
16:18:42.312 ->   CO2: 560
16:18:52.305 -> 255 134 2 62 75 0 0 1 238 
16:18:52.339 ->   CO2: 574

Bill of materials (prices as at Jan 2019)

After these tentative fixes for the MH-Z16 sensor I think going to see if there are any other libraries written by someone smarter than me available.

Grove Base Hat for Raspberry PI Windows 10 IoT Core

After some experimentation I have a proof of concept Windows 10 IoT Core library for accessing the Analog to Digital Convertor (ADC) on a Grove Base Hat for Raspberry PI.

I can read the raw, voltage & % values just fine but the Version number isn’t quite what I expected. In the python sample code I can see the register numbers etc.

def __init__(self, address=0x04):
self.address = address
self.bus = grove.i2c.Bus()

def read_raw(self, channel):
addr = 0x10 + channel
return self.read_register(addr)

# read input voltage (mV)
def read_voltage(self, channel):
addr = 0x20 + channel
return self.read_register(addr)

# input voltage / output voltage (%)
def read(self, channel):
addr = 0x30 + channel
return self.read_register(addr)

@property
def name(self):
id = self.read_register(0x0)
if id == RPI_HAT_PID:
return RPI_HAT_NAME
elif id == RPI_ZERO_HAT_PID:
return RPI_ZERO_HAT_NAME

@property
def version(self):
return self.read_register(0x3)

When I read register 0x3 to get the version info the value changes randomly. Format = register num, byte value, word value

0,4,4 1,134,10374 2,2,2 3,82,79 4,0,0 5,0,0 6,0,0 7,0,0 8,0,0 9,0,0 10,0,0 11,0,0 12,0,0 13,0,0 14,0,0 15,0,0 
0,4,4 1,134,10374 2,2,2 3,86,69 4,0,0 5,0,0 6,0,0 7,0,0 8,0,0 9,0,0 10,0,0 11,0,0 12,0,0 13,0,0 14,0,0 15,0,0 
0,4,4 1,134,10374 2,2,2 3,32,66 4,0,0 5,0,0 6,0,0 7,0,0 8,0,0 9,0,0 10,0,0 11,0,0 12,0,0 13,0,0 14,0,0 15,0,0 

It looks like register 1 or 2 (134/10374 or 2/2) might contain the device version information.

The code is available on GitHub here. Next time I purchase some gear from Seeedstudio I’ll include a Grove Base Hat For Raspberry PI Zero and extend the software so they work as well.

public sealed class StartupTask : IBackgroundTask
{
   private ThreadPoolTimer timer;
   private BackgroundTaskDeferral deferral;
   AnalogPorts analogPorts = new AnalogPorts();

   public void Run(IBackgroundTaskInstance taskInstance)
   {
      deferral = taskInstance.GetDeferral();

      analogPorts.Initialise();

      byte version = analogPorts.Version();
      Debug.WriteLine($"Version {version}");

      double powerSupplyVoltage = analogPorts.PowerSupplyVoltage();
      Debug.WriteLine($"Power supply voltage {powerSupplyVoltage}v");

      timer = ThreadPoolTimer.CreatePeriodicTimer(AnalogPorts, TimeSpan.FromSeconds(5));
   }

   void AnalogPorts(ThreadPoolTimer timer)
   {
      try
      {
         ushort valueRaw;
         valueRaw = analogPorts.ReadRaw(AnalogPorts.AnalogPort.A0);
         Debug.WriteLine($"A0 Raw {valueRaw}");

         double valueVoltage;
         valueVoltage = analogPorts.ReadVoltage(AnalogPorts.AnalogPort.A0);
         Debug.WriteLine($"A0 {valueVoltage}v");

         double value;
         value = analogPorts.Read(AnalogPorts.AnalogPort.A0);
         Debug.WriteLine($"A0 {value}");
      }
      catch (Exception ex)
      {
         Debug.WriteLine($"AnalogPorts Read failed {ex.Message}");
      }
   }
}

Grove Base Hat for Raspberry PI Investigation

For a couple of projects I had been using the Dexter industries GrovePI+ and the Grove Base Hat for Raspberry PI looked like a cheaper alternative for many applications, but it lacked Windows 10 IoT Core support.

My first project was to build a Inter Integrated Circuit(I2C) device scanner to check that the Grove Base Hat STM32 MCU I2C client implementation on a “played nice” with Windows 10 IoT core.

My Visual Studio 2017 project (I2C Device Scanner) scans all the valid 7bit I2C addresses and in the debug output displayed the two “found” devices, a Grove- 3 Axis Accelerometer(+-16G) (ADXL345) and the Grove Base Hat for Raspberry PI.

backgroundTaskHost.exe' (CoreCLR: CoreCLR_UWP_Domain): Loaded 'C:\Data\Users\DefaultAccount\AppData\Local\DevelopmentFiles\I2CDeviceScanner-uwpVS.Debug_ARM.Bryn.Lewis\System.Diagnostics.Debug.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.

'backgroundTaskHost.exe' (CoreCLR: CoreCLR_UWP_Domain): Loaded 'C:\Data\Users\DefaultAccount\AppData\Local\DevelopmentFiles\I2CDeviceScanner-uwpVS.Debug_ARM.Bryn.Lewis\System.Linq.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
Exception thrown: 'System.IO.FileNotFoundException' in devMobile.Windows10IoTCore.I2CDeviceScanner.winmd
WinRT information: Slave address was not acknowledged.
.......
Exception thrown: 'System.IO.FileNotFoundException' in devMobile.Windows10IoTCore.I2CDeviceScanner.winmd
WinRT information: Slave address was not acknowledged.

I2C Controller \\?\ACPI#MSFT8000#1#{a11ee3c6-8421-4202-a3e7-b91ff90188e4}\I2C1 has 2 devices
Address 0x4
Address 0x53
Raspberry PI with Grove Base Hat & ADXL345 & Rotary angle sensor
Raspberry PI with Grove Base Hat I2C test rig

The next step was to confirm I could read the device ID of the ADXL345 and the Grove Base Hat for RaspberryPI. I had to figure out the Grove Base Hat for RaspberryPI from the Seeedstudio Python code.

I2CDevicePinger ADXL345 Debug output

...
'backgroundTaskHost.exe' (CoreCLR: CoreCLR_UWP_Domain): Loaded 'C:\Data\Users\DefaultAccount\AppData\Local\DevelopmentFiles\I2CDevicePinger-uwpVS.Debug_ARM.Bryn.Lewis\System.Diagnostics.Debug.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
DeviceID 0XE5

The DeviceID for the ADXL345 matched the DEVID in the device datasheet.

I2CDevicePinger Debug output

'backgroundTaskHost.exe' (CoreCLR: CoreCLR_UWP_Domain): Loaded 'C:\Data\Users\DefaultAccount\AppData\Local\DevelopmentFiles\I2CDevicePinger-uwpVS.Debug_ARM.Bryn.Lewis\System.Diagnostics.Debug.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
DeviceID 0X4

The DeviceID for the Grove Base Hat for RaspberryPI matched

RPI_HAT_PID = 0x0004 in the Python code.

The last test application reads the raw value of the specified analog input

public async void Run(IBackgroundTaskInstance taskInstance)
{
   string aqs = I2cDevice.GetDeviceSelector();
   DeviceInformationCollection I2CBusControllers = await DeviceInformation.FindAllAsync(aqs);

   if (I2CBusControllers.Count != 1)
   {
      Debug.WriteLine("Unexpect number of I2C bus controllers found");
      return;
   }

   I2cConnectionSettings settings = new I2cConnectionSettings(0x04)
   {
      BusSpeed = I2cBusSpeed.StandardMode,
      SharingMode = I2cSharingMode.Shared,
   };

   using (I2cDevice device = I2cDevice.FromIdAsync(I2CBusControllers[0].Id, settings).AsTask().GetAwaiter().GetResult())
   {
      try
      {
         ushort value = 0;
         // From the Seeedstudio python
	 // 0x10 ~ 0x17: ADC raw data
	 // 0x20 ~ 0x27: input voltage
         // 0x29: output voltage (Grove power supply voltage)
         // 0x30 ~ 0x37: input voltage / output voltage						
         do
	 {
            byte[] writeBuffer = new byte[1] { 0x10 };
            byte[] readBuffer = new byte[2] { 0, 0 };

            device.WriteRead(writeBuffer, readBuffer);
            value = BitConverter.ToUInt16(readBuffer, 0);

            Debug.WriteLine($"Value {value}");

            Task.Delay(1000).GetAwaiter().GetResult();
         }
         while (value != 0);
      }
      Catch (Exception ex)
      {
         Debug.WriteLine(ex.Message);
      }
   }
}

GroveBaseHatRPIRegisterReader Debug output

'backgroundTaskHost.exe' (CoreCLR: CoreCLR_UWP_Domain): Loaded 'C:\Data\Users\DefaultAccount\AppData\Local\DevelopmentFiles\GroveBaseHatRPIRegisterReader-uwpVS.Debug_ARM.Bryn.Lewis\System.Diagnostics.Debug.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
Value 3685
Value 3685
Value 3688
Value 3681
Value 3681
Value 3688
Value 3688
Value 3683

The output changed when I adjusted the rotary angle sensor (0-4095) which confirmed I could reliably read the Analog input values.

The code for my test harness applications is available on github, the next step is to build a library for the Grove Base Hat for RaspberryPI

SparkFun Pro RF – LoRa, 915MHz Payload Addressing Client

Last week a package arrived from NiceGear with a SparkFun Pro RF – LoRa, 915MHz and some cables. With this gear I have built yet another client for my Azure IoT Hub and AdaFruit.IOLoRa Field Gateways.

Now that the device is running well, I’ll look at reducing power consumption and splitting the the payload packing code into a library. Also noticed an extra “,” on the end of a message so need to come up with a better way of doing the payload packing.

/*
  Copyright ® 2018 December devMobile Software, All Rights Reserved

  THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
  KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
  PURPOSE.

  You can do what you want with this code, acknowledgment would be nice.

  http://www.devmobile.co.nz

*/
#include <stdlib.h>

#include <LoRa.h>
#include <avr/dtostrf.h>
#include "DHT.h"

#define DEBUG
//#define DEBUG_TELEMETRY
//#define DEBUG_LORA

// LoRa field gateway configuration (these settings must match your field gateway)
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const char DeviceAddress[] = {"SparkFunX1"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int InterruptPin = 12;
const int ChipSelectPin = 6;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const int LoopSleepDelaySeconds = 10 ;

const byte PayloadSizeMaximum = 64 ;
byte payload[PayloadSizeMaximum];
byte payloadLength = 0 ;

#define DHTPIN 4     // what digital pin we're connected to

// Uncomment whatever type you're using!
//#define DHTTYPE DHT11   // DHT 11
#define DHTTYPE DHT22   // DHT 22  (AM2302), AM2321
//#define DHTTYPE DHT21   // DHT 21 (AM2301)

DHT dht(DHTPIN, DHTTYPE);


void setup()
{
  SerialUSB.begin(9600);
#ifdef DEBUG
  while (!SerialUSB);
#endif
  SerialUSB.println("Setup called");

  SerialUSB.println("LoRa setup start");
  
  // override the default chip select and reset pins
  LoRa.setPins(InterruptPin, ChipSelectPin); 
  if (!LoRa.begin(FieldGatewayFrequency))
  {
    SerialUSB.println("LoRa begin failed");
    while (true); // Drop into endless loop requiring restart
  }

  // Need to do this so field gateways pays attention to messsages from this device
  LoRa.enableCrc();
  LoRa.setSyncWord(FieldGatewaySyncWord);

#ifdef DEBUG_LORA
  LoRa.dumpRegisters(SerialUSB);
#endif
  SerialUSB.println("LoRa Setup done.");

  // Configure the Seeedstudio TH02 temperature & humidity sensor
  SerialUSB.println("DHT setup start");
  dht.begin();
  delay(100);
  SerialUSB.println("DHT setup done");

  PayloadHeader((byte*)FieldGatewayAddress,strlen(FieldGatewayAddress), (byte*)DeviceAddress, strlen(DeviceAddress));

  SerialUSB.println("Setup done");
  SerialUSB.println();
}


void loop()
{
  float temperature = 17.2;
  float humidity = 75.0;

  SerialUSB.println("Loop called");

  PayloadReset();

  // Read the temperature & humidity & battery voltage values then display nicely
  temperature = dht.readTemperature();
  humidity = dht.readHumidity();
  if (isnan(humidity) || isnan(temperature)) 
  {
    SerialUSB.println("Failed to read from DHT sensor!");
    return;
  } 
   
  SerialUSB.print("T:");
  SerialUSB.print( temperature, 1 ) ;
  SerialUSB.println( "C " ) ;
  PayloadAdd( "T", temperature, 1);

  SerialUSB.print("H:");
  SerialUSB.print( humidity, 0 ) ;
  SerialUSB.println( "% " ) ;
  PayloadAdd( "H", humidity, 0) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println();
  SerialUSB.print( "RFM9X/SX127X Payload length:");
  SerialUSB.print( payloadLength );
  SerialUSB.println( " bytes" );
#endif

  LoRa.beginPacket();
  LoRa.write( payload, payloadLength );
  LoRa.endPacket();

  SerialUSB.println("Loop done");
  SerialUSB.println();
  delay(LoopSleepDelaySeconds * 1000l);
}


void PayloadHeader( byte *to, byte toAddressLength, byte *from, byte fromAddressLength)
{
  byte addressesLength = toAddressLength + fromAddressLength ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadHeader- ");
  SerialUSB.print( "To Address len:");
  SerialUSB.print( toAddressLength );
  SerialUSB.print( " From Address len:");
  SerialUSB.print( fromAddressLength );
  SerialUSB.print( " Addresses length:");
  SerialUSB.print( addressesLength );
  SerialUSB.println( );
#endif

  payloadLength = 0 ;

  // prepare the payload header with "To" Address length (top nibble) and "From" address length (bottom nibble)
  payload[payloadLength] = (toAddressLength << 4) | fromAddressLength ;
  payloadLength += 1;

  // Copy the "To" address into payload
  memcpy(&payload[payloadLength], to, toAddressLength);
  payloadLength += toAddressLength ;

  // Copy the "From" into payload
  memcpy(&payload[payloadLength], from, fromAddressLength);
  payloadLength += fromAddressLength ;
}


void PayloadAdd( char *sensorId, float value, byte decimalPlaces)
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-float ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value, decimalPlaces );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( dtostrf(value, -1, decimalPlaces, (char *)&payload[payloadLength]));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadAdd( char *sensorId, int value )
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-int ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif  

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( itoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadAdd( char *sensorId, unsigned int value )
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-unsigned int ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif  

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( utoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadReset()
{
  byte fromAddressLength = payload[0] & 0xf ;
  byte toAddressLength = payload[0] >> 4 ;
  byte addressesLength = toAddressLength + fromAddressLength ;

  payloadLength = addressesLength + 1;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadReset- ");
  SerialUSB.print( "To Address len:");
  SerialUSB.print( toAddressLength );
  SerialUSB.print( " From Address len:");
  SerialUSB.print( fromAddressLength );
  SerialUSB.print( " Addresses length:");
  SerialUSB.print( addressesLength );
  SerialUSB.println( );
#endif
}
  • SparkFun Pro RF – LoRa, 915MHz USD29.95 NZD49
  • Grove – Temperature & Humidity Sensor Pro (AM2302) USD9.90
  • Seeedstudio 4 pin Male Jumper to Grove 4 pin Conversion Cable USD2.90

Moteino M0 Payload Addressing client

Last week a package arrived from LowPowerLab with some Moteino0 devices and accessories . With this gear I have built yet another client for my Azure IoT Hub and AdaFruit.IOLoRa Field Gateways.

It took me a while longer that usual to get the Motenio working as the sketch setup call appeared to hang in DEBUG builds.

After staring at the code for a while I noticed that I hadn’t changed LoRa.dumpRegisters method parameter from Serial to SerialUSB. A couple of hours lost due to a dumb typo by me.

Now that the device is running well, I’ll look at reducing power consumption and splitting the the payload packing code into a library.

/*
  Copyright ® 2018 November devMobile Software, All Rights Reserved

  THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
  KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
  PURPOSE.

  You can do what you want with this code, acknowledgment would be nice.

  http://www.devmobile.co.nz

*/
#include <stdlib.h>
#include <avr/dtostrf.h>
#include <LoRa.h>
#include <TH02_dev.h>

//#define DEBUG
//#define DEBUG_TELEMETRY
//#define DEBUG_LORA

// LoRa field gateway configuration (these settings must match your field gateway)
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const char DeviceAddress[] = {"Moteino01"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int ChipSelectPin = A2;
const int InterruptPin = 9;
const int ResetPin = -1;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const int LoopSleepDelaySeconds = 10 ;

const byte PayloadSizeMaximum = 64 ;
byte payload[PayloadSizeMaximum];
byte payloadLength = 0 ;


void setup()
{
  SerialUSB.begin(9600);
#ifdef DEBUG
  while (!SerialUSB);
#endif
  SerialUSB.println("Setup called");

  SerialUSB.println("LoRa setup start");
  
  // override the default chip select and reset pins
  LoRa.setPins( ChipSelectPin, ResetPin, InterruptPin ); 
  if (!LoRa.begin(FieldGatewayFrequency))
  {
    SerialUSB.println("LoRa begin failed");
    while (true); // Drop into endless loop requiring restart
  }

  // Need to do this so field gateways pays attention to messsages from this device
  LoRa.enableCrc();
  LoRa.setSyncWord(FieldGatewaySyncWord);

#ifdef DEBUG_LORA
  LoRa.dumpRegisters(USBSerial);
#endif
  SerialUSB.println("LoRa Setup done.");

  // Configure the Seeedstudio TH02 temperature & humidity sensor
  SerialUSB.println("TH02 setup start");
  TH02.begin();
  delay(100);
  SerialUSB.println("TH02 setup done");

  PayloadHeader((byte*)FieldGatewayAddress,strlen(FieldGatewayAddress), (byte*)DeviceAddress, strlen(DeviceAddress));

  SerialUSB.println("Setup done");
  SerialUSB.println();
}


void loop()
{
  float temperature ;
  float humidity ;

  SerialUSB.println("Loop called");

  PayloadReset();

  // Read the temperature & humidity & battery voltage values then display nicely
  temperature = TH02.ReadTemperature();
  SerialUSB.print("T:");
  SerialUSB.print( temperature, 1 ) ;
  SerialUSB.println( "C " ) ;

  PayloadAdd( "T", temperature, 1);

  humidity = TH02.ReadHumidity();
  SerialUSB.print("H:");
  SerialUSB.print( humidity, 0 ) ;
  SerialUSB.println( "% " ) ;

  PayloadAdd( "H", humidity, 0) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println();
  SerialUSB.print( "RFM9X/SX127X Payload length:");
  SerialUSB.print( payloadLength );
  SerialUSB.println( " bytes" );
#endif

  LoRa.beginPacket();
  LoRa.write( payload, payloadLength );
  LoRa.endPacket();

  SerialUSB.println("Loop done");
  SerialUSB.println();
  delay(LoopSleepDelaySeconds * 1000l);
}


void PayloadHeader( byte *to, byte toAddressLength, byte *from, byte fromAddressLength)
{
  byte addressesLength = toAddressLength + fromAddressLength ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadHeader- ");
  SerialUSB.print( "To Address len:");
  SerialUSB.print( toAddressLength );
  SerialUSB.print( " From Address len:");
  SerialUSB.print( fromAddressLength );
  SerialUSB.print( " Addresses length:");
  SerialUSB.print( addressesLength );
  SerialUSB.println( );
#endif

  payloadLength = 0 ;

  // prepare the payload header with "To" Address length (top nibble) and "From" address length (bottom nibble)
  payload[payloadLength] = (toAddressLength << 4) | fromAddressLength ;
  payloadLength += 1;

  // Copy the "To" address into payload
  memcpy(&payload[payloadLength], to, toAddressLength);
  payloadLength += toAddressLength ;

  // Copy the "From" into payload
  memcpy(&payload[payloadLength], from, fromAddressLength);
  payloadLength += fromAddressLength ;
}


void PayloadAdd( const char *sensorId, float value, byte decimalPlaces)
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-float ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value, decimalPlaces );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( dtostrf(value, -1, decimalPlaces, (char *)&payload[payloadLength]));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadAdd( const char *sensorId, int value )
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-int ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif  

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( itoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadAdd( const char *sensorId, unsigned int value )
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-unsigned int ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif  

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( utoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadReset()
{
  byte fromAddressLength = payload[0] & 0xf ;
  byte toAddressLength = payload[0] >> 4 ;
  byte addressesLength = toAddressLength + fromAddressLength ;

  payloadLength = addressesLength + 1;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadReset- ");
  SerialUSB.print( "To Address len:");
  SerialUSB.print( toAddressLength );
  SerialUSB.print( " From Address len:");
  SerialUSB.print( fromAddressLength );
  SerialUSB.print( " Addresses length:");
  SerialUSB.print( addressesLength );
  SerialUSB.println( );
#endif
}
Azure IoT Central

Bill of materials (prices as at November 2018)

  • Moteino M0 USD34.95
  • Seeedstudio Temperature and Humidity Sensor Pro USD11.50
  • Seeedstudio 4 pin Male Jumper to Grove 4 pin Conversion Cable USD2.90