Random wanderings through Microsoft Azure esp. PaaS plumbing, the IoT bits, AI on Micro controllers, AI on Edge Devices, .NET nanoFramework, .NET Core on *nix and ML.NET+ONNX
Important: make sure you setup the I2C pins especially on ESP32 Devices before creating the I2cDevice,
SHT20 +STM32F769 Discovery test rig
The .NET nanoFramework device libraries use a TryGet… pattern to retrieve sensor values, this library throws an exception if reading a sensor value fails. I’m not certain which approach is “better” as reading the Seeedstudio Grove – Laser PM2.5 Dust Sensor has never failed. The only time reading the “values” buffer failed was when I unplugged the device which I think is “exceptional”.
//---------------------------------------------------------------------------------
// Copyright (c) April 2023, devMobile Software
//
// 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.
//
// nanoff --target ST_STM32F769I_DISCOVERY --update
// nanoff --platform ESP32 --serialport COM7 --update
//
//---------------------------------------------------------------------------------
#define ST_STM32F769I_DISCOVERY
//#define SPARKFUN_ESP32_THING_PLUS
namespace devMobile.IoT.Device.SeeedstudioHM3301
{
using System;
using System.Device.I2c;
using System.Threading;
#if SPARKFUN_ESP32_THING_PLUS
using nanoFramework.Hardware.Esp32;
#endif
class Program
{
static void Main(string[] args)
{
const int busId = 1;
Thread.Sleep(5000);
#if SPARKFUN_ESP32_THING_PLUS
Configuration.SetPinFunction(Gpio.IO23, DeviceFunction.I2C1_DATA);
Configuration.SetPinFunction(Gpio.IO22, DeviceFunction.I2C1_CLOCK);
#endif
I2cConnectionSettings i2cConnectionSettings = new(busId, SeeedstudioHM3301.DefaultI2cAddress);
using I2cDevice i2cDevice = I2cDevice.Create(i2cConnectionSettings);
{
using (SeeedstudioHM3301 seeedstudioHM3301 = new SeeedstudioHM3301(i2cDevice))
{
while (true)
{
SeeedstudioHM3301.ParticulateMeasurements particulateMeasurements = seeedstudioHM3301.Read();
Console.WriteLine($"Standard PM1.0: {particulateMeasurements.Standard.PM1_0} ug/m3 PM2.5: {particulateMeasurements.Standard.PM2_5} ug/m3 PM10.0: {particulateMeasurements.Standard.PM10_0} ug/m3 ");
Console.WriteLine($"Atmospheric PM1.0: {particulateMeasurements.Atmospheric.PM1_0} ug/m3 PM2.5: {particulateMeasurements.Atmospheric.PM2_5} ug/m3 PM10.0: {particulateMeasurements.Standard.PM10_0} ug/m3");
// Always 0, checked payload so not a conversion issue. will check in Seeedstudio forums
// Console.WriteLine($"Count 0.3um: {particulateMeasurements.Count.Diameter0_3}/l 0.5um: {particulateMeasurements.Count.Diameter0_5} /l 1.0um : {particulateMeasurements.Count.Diameter1_0}/l 2.5um : {particulateMeasurements.Count.Diameter2_5}/l 5.0um : {particulateMeasurements.Count.Diameter5_0}/l 10.0um : {particulateMeasurements.Count.Diameter10_0}/l");
Thread.Sleep(new TimeSpan(0,1,0));
}
}
}
}
}
}
I’m going to soak test the library for a week to check that is working okay, then most probably refactor the code so it can be added to the nanoFramework IoT.Device Library repository.
The unpacking of the value standard particulate, particulate count and particle count values is fairly repetitive, but I will fix it in the next version.
Visual Studio 2022 Debug output
The checksum calculation isn’t great even a simple cyclic redundancy check(CRC) would be an improvement on summing the 28 bytes of the payload.
The Seeeduino Nano devices I’m testing have a single on-board I2C socket which meant I didn’t need a Grove Shield for Arduino Nano which reduced the size and cost of the sensor node.
After looking at the demo application I stripped out the checksum code and threw the rest away. In my test harness I have extracted only the PM1.0/PM2.5/PM10.0 (concentration CF=1, Standard particulate) in μg/ m3 values from the sensor response payload.
/*
Copyright ® 2019 August 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 <sha204_library.h>
#include "Seeed_HM330X.h"
//#define DEBUG
//#define DEBUG_TELEMETRY
//#define DEBUG_LORA
const byte SensorPayloadLength = 28 ;
const byte SensorPayloadBufferSize = 29 ;
const byte SensorPayloadPM1_0Position = 4;
const byte SensorPayloadPM2_5Position = 6;
const byte SensorPayloadPM10_0Position = 8;
HM330X sensor;
byte SensorPayload[SensorPayloadBufferSize];
// LoRa field gateway configuration (these settings must match your field gateway)
const byte DeviceAddressMaximumLength = 15 ;
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const float FieldGatewayFrequency = 915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;
// Payload configuration
const int ChipSelectPin = 10;
const int ResetPin = 9;
const int InterruptPin = 2;
// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const unsigned long SensorUploadDelay = 60000;
// ATSHA204 secure authentication, validation with crypto and hashing (currently only using for unique serial number)
const byte Atsha204Port = A3;
atsha204Class sha204(Atsha204Port);
const byte DeviceSerialNumberLength = 9 ;
byte deviceSerialNumber[DeviceSerialNumberLength] = {""};
const byte PayloadSizeMaximum = 64 ;
byte payload[PayloadSizeMaximum];
byte payloadLength = 0 ;
void setup()
{
Serial.begin(9600);
#ifdef DEBUG
while (!Serial);
#endif
Serial.println("Setup called");
Serial.print("Field gateway:");
Serial.print(FieldGatewayAddress ) ;
Serial.print(" Frequency:");
Serial.print( FieldGatewayFrequency,0 ) ;
Serial.print("MHz SyncWord:");
Serial.print( FieldGatewaySyncWord ) ;
Serial.println();
// Retrieve the serial number then display it nicely
if(sha204.getSerialNumber(deviceSerialNumber))
{
Serial.println("sha204.getSerialNumber failed");
while (true); // Drop into endless loop requiring restart
}
Serial.print("SNo:");
DisplayHex( deviceSerialNumber, DeviceSerialNumberLength);
Serial.println();
Serial.println("LoRa setup start");
// override the default chip select and reset pins
LoRa.setPins(ChipSelectPin, ResetPin, InterruptPin);
if (!LoRa.begin(FieldGatewayFrequency))
{
Serial.println("LoRa begin failed");
while (true); // Drop into endless loop requiring restart
}
// Need to do this so field gateway pays attention to messsages from this device
LoRa.enableCrc();
LoRa.setSyncWord(FieldGatewaySyncWord);
#ifdef DEBUG_LORA
LoRa.dumpRegisters(Serial);
#endif
Serial.println("LoRa Setup done.");
// Configure the Seeedstudio CO2, temperature & humidity sensor
Serial.println("HM3301 setup start");
if(sensor.init())
{
Serial.println("HM3301 init failed");
while (true); // Drop into endless loop requiring restart
}
delay(100);
Serial.println("HM3301 setup done");
PayloadHeader((byte *)FieldGatewayAddress,strlen(FieldGatewayAddress), deviceSerialNumber, DeviceSerialNumberLength);
Serial.println("Setup done");
Serial.println();
}
void loop()
{
unsigned long currentMilliseconds = millis();
byte sum=0;
short pm1_0 ;
short pm2_5 ;
short pm10_0 ;
Serial.println("Loop called");
if(sensor.read_sensor_value(SensorPayload,SensorPayloadBufferSize) == NO_ERROR)
{
// Calculate then validate the payload "checksum"
for(int i=0;i<SensorPayloadLength;i++)
{
sum+=SensorPayload[i];
}
if(sum!=SensorPayload[SensorPayloadLength])
{
Serial.println("Invalid checksum");
return;
}
PayloadReset();
pm1_0 = (u16)SensorPayload[SensorPayloadPM1_0Position]<<8|SensorPayload[SensorPayloadPM1_0Position+1];
Serial.print("PM1.5: ");
Serial.print(pm1_0);
Serial.println("ug/m3 ") ;
PayloadAdd( "P10", pm1_0, false);
pm2_5 = (u16)SensorPayload[SensorPayloadPM2_5Position]<<8|SensorPayload[SensorPayloadPM2_5Position+1];
Serial.print("PM2.5: ");
Serial.print(pm2_5);
Serial.println("ug/m3 ") ;
PayloadAdd( "P25", pm2_5, 1, false);
pm10_0 = (u16)SensorPayload[SensorPayloadPM10_0Position]<<8|SensorPayload[SensorPayloadPM10_0Position+1];
Serial.print("PM10.0: ");
Serial.print(pm10_0);
Serial.println("ug/m3 ");
PayloadAdd( "P100", pm10_0, 0, true) ;
#ifdef DEBUG_TELEMETRY
Serial.println();
Serial.print("RFM9X/SX127X Payload length:");
Serial.print(payloadLength);
Serial.println(" bytes");
#endif
LoRa.beginPacket();
LoRa.write(payload, payloadLength);
LoRa.endPacket();
}
Serial.println("Loop done");
Serial.println();
delay(SensorUploadDelay - (millis() - currentMilliseconds ));
}
void PayloadHeader( const byte *to, byte toAddressLength, const byte *from, byte fromAddressLength)
{
byte addressesLength = toAddressLength + fromAddressLength ;
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, bool last)
{
byte sensorIdLength = strlen( sensorId ) ;
memcpy( &payload[payloadLength], sensorId, sensorIdLength) ;
payloadLength += sensorIdLength ;
payload[ payloadLength] = SensorIdValueSeperator;
payloadLength += 1 ;
payloadLength += strlen( dtostrf(value, -1, decimalPlaces, (char *)&payload[payloadLength]));
if (!last)
{
payload[ payloadLength] = SensorReadingSeperator;
payloadLength += 1 ;
}
#ifdef DEBUG_TELEMETRY
Serial.print("PayloadAdd float-payloadLength:");
Serial.print( payloadLength);
Serial.println( );
#endif
}
void PayloadAdd( char *sensorId, int value, bool last )
{
byte sensorIdLength = strlen(sensorId) ;
memcpy(&payload[payloadLength], sensorId, sensorIdLength) ;
payloadLength += sensorIdLength ;
payload[ payloadLength] = SensorIdValueSeperator;
payloadLength += 1 ;
payloadLength += strlen(itoa( value,(char *)&payload[payloadLength],10));
if (!last)
{
payload[ payloadLength] = SensorReadingSeperator;
payloadLength += 1 ;
}
#ifdef DEBUG_TELEMETRY
Serial.print("PayloadAdd int-payloadLength:" );
Serial.print(payloadLength);
Serial.println( );
#endif
}
void PayloadAdd( char *sensorId, unsigned int value, bool last )
{
byte sensorIdLength = strlen(sensorId) ;
memcpy(&payload[payloadLength], sensorId, sensorIdLength) ;
payloadLength += sensorIdLength ;
payload[ payloadLength] = SensorIdValueSeperator;
payloadLength += 1 ;
payloadLength += strlen(utoa( value,(char *)&payload[payloadLength],10));
if (!last)
{
payload[ payloadLength] = SensorReadingSeperator;
payloadLength += 1 ;
}
#ifdef DEBUG_TELEMETRY
Serial.print("PayloadAdd uint-payloadLength:");
Serial.print(payloadLength);
Serial.println( );
#endif
}
void PayloadReset()
{
byte fromAddressLength = payload[0] & 0xf ;
byte toAddressLength = payload[0] >> 4 ;
payloadLength = toAddressLength + fromAddressLength + 1;
}
void DisplayHex( byte *byteArray, byte length)
{
for (int i = 0; i < length ; i++)
{
// Add a leading zero
if ( byteArray[i] < 16)
{
Serial.print("0");
}
Serial.print(byteArray[i], HEX);
if ( i < (length-1)) // Don't put a - after last digit
{
Serial.print("-");
}
}
}
To configure the device in Azure IoT Central (similar process for Adafruit.IO, working on support for losant, and ubidots) I copied the SNo: from the Arduino development tool logging window and appended p10 for PM 1 value, p25 for PM2.5 value and p100 for PM10 value to the unique serial number from the ATSHA204A chip. (N.B. pay attention to the case of the field names they are case sensitive)
Azure IoT Central telemetry configuration
The rapidly settled into a narrow range of readings, but spiked when I took left it outside (winter in New Zealand) and the values spiked when food was being cooked in the kitchen which is next door to my office.
It would be good to run the sensor alongside a professional particulates monitor so the values could be compared and used to adjust the readings of the Grove sensor if necessary.
Hour of PM1, PM2.5 & PM10 readings in my office early eveningCO2 and particulates values while outside on my deck from 10:30pm to 11:30pm
devMobile's blog 