File content as of revision 2:65f09ca5b557:

/* Run Honeywell Dust Sensor in continous Sampling Mode on a mDot
   Version 1.0
   Steve Mylroie Roitronic August 1st 2017
   @C Copyright Global Quality Corp
*/

#include "mbed.h"
#include "mDot.h"
#include "MTSLog.h"
#include "stdlib.h"
#include <Stream.h>

#define TRACE_MODE

//Turn on trace logging to the PC USB port
#ifdef TRACE_MODE
//Log level need to be set one level higher than the high level to be output
#define LOG_LEVEL mts::MTSLog::TRACE_LEVEL + 1
#define DEBUG
#endif

const uint8_t* measureCommand = "68014057";
const uint8_t* stopCommand    = "68012077";

#define OK   0xA5A5
#define BAD  0x9696

#define MESSAGE_LEN 32
//sensor measurement cycle in millseconds
#define MEASURE_DELAY 1500 

//Use USB debug pott for the debug stream
#ifdef DEBUG
Serial pc(USBTX, USBRX, 115200);
#endif

//Use second UART to communicate witb the Honneywell sensor
//Default UART setting are 8,N,1
Serial sensor(PA_2, PA_3 , 9600);

Timer t;

//synchrnous serial read and writes
//Mbed 5 Serial class only supports single character read and writes or
// async buffer reads abd wrutes
void readBuffer(uint8_t* buffer, uint16_t count)
{
    uint8_t* pointer = buffer;
    uint16_t counter = count;
    while(1)
    {
        if(sensor.readable())
        {
            *pointer++ = sensor.getc();
            counter--;
            }
        if(count == 0) {
            return;
            }
        }
    }
    
void writeBuffer(const uint8_t* buffer, uint16_t count)
{
    uint8_t* pointer = (uint8_t*)buffer;
    uint16_t counter = count;
    while(1)
    {
        if(sensor.writeable())
        {
            sensor.putc(*pointer++);
            counter--;
            }
        if(count == 0) {
            return;
            }
        }
    } 

//Va;idate the received mesurements checksum

bool checkValue(uint8_t *thebuf, uint8_t leng)
{  
  bool receiveflag = false;
  uint16_t receiveSum=0;

  for(int i=0; i<(leng-2); i++){
  receiveSum=receiveSum+thebuf[i];
  }
  receiveSum=receiveSum + 0x42;
 
  if(receiveSum == ((thebuf[leng-2]<<8)+thebuf[leng-1]))  //check the debug data 
  {
    receiveSum = 0;
    receiveflag = true;
  }
  return receiveflag;
}

//Extract the 1 micron particle count from the messaage
uint16_t transmitPM01(uint8_t *thebuf)
{
  uint16_t PM01Val;
  PM01Val=((thebuf[3]<<8) + thebuf[4]); //count PM1.0 value of the air detector module
  return PM01Val;
}

//Extract the 2.5 micron particle count from the messaage
uint16_t transmitPM2_5(uint8_t *thebuf)
{
  uint16_t PM2_5Val;
  PM2_5Val=((thebuf[5]<<8) + thebuf[6]);//count PM2.5 value of the air detector module
  return PM2_5Val;
  }

//Extract the 10 micron particle count from the messaage
uint16_t transmitPM10(uint8_t *thebuf)
{
  uint16_t PM10Val;
  PM10Val=((thebuf[7]<<8) + thebuf[8]); //count PM10 value of the air detector module  
  return PM10Val;
}

int main()
{
    uint8_t dataBuffer[32];
    uint16_t response;
    uint16_t PM01Value=0;     //define PM1.0 value of the air detector module
    uint16_t PM2_5Value=0;        //define PM2.5 value of the air detector module
    uint16_t PM10Value=0;         //define PM10 value of the air detector module

    //Send start command to the sensor
    writeBuffer(measureCommand, 4);
    //Wait for sensors response
    //while(!sensor.readable());
    readBuffer(dataBuffer, 2);
    response = dataBuffer[0] << 8 || dataBuffer[1];

    switch(response) {
        case OK:
        logInfo("Sensor Auto Measurement Started");
        break;
        case BAD:
        logInfo("Sensor rejected Start Measurement Commmand");
        return -1;
        default:
        logInfo("Communication Error: Invalid Sensor Response");
        return -2;
    }
    t.start();
    
    //Start continous loop 
    while(1)
    {
       if(sensor.getc() == 0x42){    //start to read when detect 0x42
            readBuffer(dataBuffer,MESSAGE_LEN -1);
        
            if(dataBuffer[0] == 0x4d){
              if(checkValue(dataBuffer,MESSAGE_LEN)){
                PM01Value=transmitPM01(dataBuffer); //count PM1.0 value of the air detector module
                PM2_5Value=transmitPM2_5(dataBuffer);//count PM2.5 value of the air detector module
                PM10Value=transmitPM10(dataBuffer); //count PM10 value of the air detector module 
              }
          }           
        }
        
        char input = pc.getc();
        if(input == 'Q' || input == 'q')
        { 
            t.stop();
            writeBuffer(stopCommand, 4);
            logInfo("Exit request received");
            return 0;
        }
        static unsigned long OledTimer= t.read_ms();  
        if (t.read_ms() - OledTimer >=1000) 
        {
          OledTimer= t.read_ms(); 
          
          pc.printf("PM1.0: %d ug/m3", PM01Value);  
//          debug.print(PM01Value);
//          debug.println("  ug/m3");            
        
          pc.printf("PM2.5: %d ug/m3", PM2_5Value);  
//          debug.print(PM2_5Value);
//          debug.println("  ug/m3");     
          
          pc.printf("PM10: %d ug/m3", PM10Value);  
//          debug.print(PM10Value);
//          debug.println("  ug/m3");   
          pc.printf("\n");
            
        }
    }
 }