Published January 21, 2019

Study of Grounds for ST

An engineering school project.

IntermediateShowcase (no instructions)893

Things used in this project

Hardware components

STM32 Nucleo L432KC

DHT22 Temperature Sensor

Adafruit Waterproof DS18B20 Digital temperature sensor

DFRobot SEN0193

Adafruit BMP183

Seeed Studio MPU9250

Software apps and online services

Arm mbed

Sigfox

Ubidots

Node-RED on IBM Cloud

Story

We are 3 engineering students at Polytech Sorbonne specialised in electronics and computer science. Our project is to help others students in their work. We have to gather a lot of different DATAs like the temperature of the ground and the air, the humidity...

Problematics : Our project need to have a low consumption, resist to water and be durable, because it is meant to be in the wild on mountains

A microcontroller recovers sensor's datas and it displays on a screen the information in real time. It also send those datas to an online server called Ubidots via a SigFox Antenna.

This system is completely autonomous : it is supplied by a battery charged by a solar panel, and is awaken ones every hour to collect and send the data.

1) The code

To develop our project, we used Mbed. It's an online programming software. Its particularity is that it is a collaborative platform, you can find a lot of library supported by thoses sensor. It's easy to use.

To consume the least amount of energy possible, we used the sleep mode on the card, which make our box consumming little to nothing whenever it wait. We decided to wake it once everyhour to collect and send the datas before going to sleep again.

Futhermore, a little switch permit the box to use it LCD display, only when people are around since they can turn it off when they let the box in the wild.

2) Online Server

We used Sigfox technology, to send datas, then via a callback everything is send to ubidot in Json format Text. This technology is interesting because it has a really good coverage and fits perfectly our project problematics to send datas from the Alps for example.

All datas can be displayed on a dashboard. Everything can then be downloded in CSV file. To be a little more precise our datas, every variable are times 100 when send to be divided in ubidot by 100, and obtain floatings datas

3) The Card

We choose ALTIUM DESIGNER to create our PCB. On this card, we place our microcontroller and all sensors.

Code

Programme main

// PROGRAMME PRINCIPALE

#include "mbed.h"
#include "DHT.h"
#include "ssd1306.h"
#include "standard_font.h"
#include "bold_font.h"
#include "DS1820.h"
#include "BMP183.h"
//#include "MPU9250.h"

#define TIMERR 2
#define DEBUG 0
#define SLEEPTIME 3600

Serial sig(D1,D0);
Serial sig2(USBTX,USBRX);

DigitalOut ChipSelectBaro(A3);
//SPI spi(SPI_MOSI, SPI_MISO, SPI_SCK)
SPI spi(D11, D12, D13);

AnalogIn moisture(A0);

DHT C1(A2,AM2302);

DigitalOut myled(LED1);

SSD1306 oled(D3 /* cs */, D6/* reset */, A5 /* dc */,
             A4 /* clock */, D2 /* data */);

DS1820 probe(A1);

int Dht22(void);
int Ds1820(void);
int Sen0193(void);
int Baro(BMP183 baro);
int InitBaro(BMP183 baro);

float temp,hum,tempS;
float pres,alt;
float humS;

int varReveil;
void callbackReveil (void){
    varReveil = 0;
}
Ticker flipper;


int main()
{
     int test =0;
     
   // BMP183 baro(SPI_MOSI, SPI_MISO, SPI_SCK, D2);
    BMP183 baro(D11, D12, D13, A3);
    oled.initialise();
    oled.clear();
    oled.set_contrast(255); // max contrast
 
    oled.set_font(bold_font, 8);
    oled.printf("Petit Callou\r\n Des Alpes\r\n");
 
    oled.set_font(standard_font, 6);
  //  oled.printf("\r\n Test program\n");
    //oled.printf("******************\r\n");
    wait(1); // wait 1 second for device stable status
 
    oled.update();

    test = InitBaro(baro);
    baro.getCalibrationData();

int i=0;
 while(1){
      
      Dht22();
      Ds1820();
      Sen0193(); 
      if(test == 1);
            Baro(baro);
      
      
        oled.printf("\r\n****Petit Caillou****\r\n");
        oled.printf("Temp Air: %2.2fC \r\nSol: %2.2fC\r\n",temp,tempS);
        oled.printf("Hum Air: %2.2f/100 \r\nSol: %2.2f/100\r\n",hum,humS/10);
        oled.printf("Pres %2.2fPa \r\nAlt: %2.2fm\r\n", pres, alt);
        oled.update();
      
      
      temp = temp*100;
      hum = hum *100;
      tempS = tempS*100;
      humS = humS/10;


      sig.printf("AT$SF=");
      sig.printf("%04x%04x%04x%04x%04x%04x",(int)temp,(int)hum,(int)tempS,(int)pres,(int)alt,(int)humS);
      sig.printf("\r\n");
      sig2.printf("AT$SF=");
      sig2.printf("%04x%04x%04x%04x%04x%04x",(int)temp,(int)hum,(int)tempS,(int)pres,(int)alt,(int)humS);
      sig2.printf("\r\n");
       if(DEBUG == 1)
     {
      oled.printf("Msg Envoye\n\r");
      }

     i++;
     
     varReveil = 1;
     flipper.attach(&callbackReveil, SLEEPTIME);
     while(varReveil==1){
        sleep(); 
        }
    flipper.detach();    
    // wait(6);
 }
    
}

int InitBaro(BMP183 baro){
    int status;
    int go = -1;
    status = baro.getID();
    
    if(status != 0x55) {
        go = -1;
        oled.printf("Communication to Baro failed...\n");
    } else {
        oled.printf("Baro OK!\n\r");
        go = 1;
    }
    return go;
}

int Baro(BMP183 baro){
    baro.read();
    
    pres = baro.Pressure;
    alt = baro.Altitude;
    if(DEBUG == 1)
    {
        oled.printf("\r\n*****BMP183****\r\n");
        oled.printf("Temp.: %f\r\n", baro.Temperature);
        oled.printf("Pres.: %f\r\n", pres);
        oled.printf("Alt.: %f\r\n", alt);
        oled.printf("***************\r\n");
        oled.update();
    }
    return 0;
}

int Ds1820(void){
    probe.convertTemperature(true, DS1820::all_devices);         //Start temperature conversion, wait until ready
    tempS = probe.temperature();
    if(DEBUG == 1)
    {
    oled.printf("\r\n*****Ds1820****\r\n");
    oled.printf("It is %3.1foC\r\n", tempS);
    oled.printf("***************\r\n");
    oled.update();
    }
   // wait(TIMERR);
    return 0;
}

int Dht22(void){
    
   // float temp,hum;
    C1.readData();
    hum = C1.ReadHumidity();
    temp = C1.ReadTemperature(CELCIUS);
     if(DEBUG == 1)
    {
    oled.printf("\r\n******DHT22******\r\n");
    oled.printf("temp =  %6.2f C\r\n", temp);
    oled.printf("hum =  %6.2f%\r\n", hum);
    oled.printf("*****************\r\n");
    oled.update();
    }
   // wait(TIMERR);
    return 0;
}


int Sen0193(void){
    
    float value = 0.0f,valuefin=0.0f;
    int valueint=0;
    value = moisture;
    valueint = moisture *100;
    valuefin = (78-valueint )* 100  / 40;
    humS=valuefin;
     if(DEBUG == 1)
    {
    oled.printf("\r\n*****SEN0193****\r\n");
    oled.printf("hum du sol : %2.2f // : %2.2f/100\n", value,valuefin);
    oled.printf("\r\n*****************\r\n");
    oled.update();
    }
   // wait(TIMERR);
    return 0;
}