Example serial communication : parsing and sending AT-commands

scoobsalamander · 2016-01-07 13:05:09

I would like to send AT-commands by means of the serial port and through the same port I would also like to receive some data which needs to be parsed to get the values....is this possible?

If yes, then some examples and/or some hints are most welcome....

jaroslav_sobota · 2016-01-08 15:42:26

Great question! Sending some status and allowing user commands via SMS text messages? Is this what you are up to?

scoobsalamander · 2016-01-08 17:33:40

No, I want to control my gas boiler which is using the Opentherm protocol.
At home I have already a long time the Opentherm Gateway which is working fine but now I want to use this one to control my boiler with the REX software through the serial port of the RasPi.

It will send messages with the status and you can control it by sending command messages...

But I might also be interested to read other serial data....like a GPS (NMEA) or data from a RFM12B receiver(with the demo software) which is getting data from all kind of different nodes. These nodes are for example used to send the roomtemperature from every single room by radio communication (868Mhz). (RFM12B @ Jeelabs)

RFM12B example messages....

Last edited by scoobsalamander (2016-01-08 22:47:34)

jaroslav_sobota · 2016-01-09 00:33:14

Even better! Did you have a look at the example on serial data exchange?

Parsing of the incoming data is quite challenging because the REXLANG language does not support strings (yet) but it is doable for smaller projects.

soxso2011 · 2017-01-15 08:23:49

Hi, I also want to read data from COM Ports and parse it and then send it to OPC!! I am trying to read the data from receiver example but its not working.Please help me out!

 #define COM_DEVICE_FNAME 17   // serial device is defined by the fname parameter of the REXLANG block (e.g. /dev/ttyS0 in Linux or COM1: in Windows)

#define COM_BAUDRATE 9600 //baudrate, e.g. 9600, 19200, 57600, 115200

#define COM_PARITY_NONE 0  //no parity
#define COM_PARITY_ODD  1  //odd parity
#define COM_PARITY_EVEN 2  //even parity

#define BUFFER_SIZE  50    //maximum number of bytes to send

//assigning variables to outputs, these variables are WRITE-ONLY
long output(0) signal0;    //integer number received from the sender
long output(1) signal1;    //integer number received from the sender
double output(2) signal2;  //real number received from the sender
double output(3) signal3;  //real number received from the sender
long output(14) receivedBytes; //number of received bytes
long output(15) handle;    //handle of the serial device

long output(10) dat0;      //the first byte of the received data
long output(11) dat1;      //the second byte of the received data
long output(12) dat2;      //the third byte of the received data
long output(13) dat3;      //the fourth byte of the received data

//declaration of variables
long hCom;                 //communication handle
long buffer[BUFFER_SIZE];  //buffer for incoming data
long dataCnt;              //number of bytes sent
long convData[2];          //array for data conversions

/* Function for conversion of 2 numbers of type Long representing a decimal 
number in the double format according to IEEE 754 to a decimal number. 
Little-endian format is used. */
double LongAsDouble(long val[])
{
	double lbase=((double)(val[1]&0xFFFFF))/((double)0x00100000)+(val[0]&0x7FFFFFFF)*pow(2.0,-52.0);
	long lexp=(val[1]>>20)&0x7FF;
	if(val[0]&0x80000000)
		lbase+=pow(2.0,-21.0);
	if(lexp==0)
		return 0.0;
	if(lexp==0x7FF)
	{	
    //deal with NaN and Inf here if necessary
		return 1.0e60; //substitute value
	}
	lbase=(lbase+1.0)*pow(2.0,(double)(lexp-1023));
	return (val[1]&0x80000000)!=0? -lbase : lbase;
}

/* Initialization of the REXLANG algorithm */
// the init procedure is executed once when the REXLANG function block initializes
long init(void)
{
  hCom = -1;
  dataCnt = 0;
	return 0;
}

/* The body of REXLANG algorithm */
// the main procedure is executed once in each sampling period
long main(void)
{
  long i;
  if (hCom<0)
  {
    hCom = Open(COM17,9600,0);  //opening serial device
  }
  else 
  {
    //receive the data
    dataCnt = Recv(hCom,buffer,BUFFER_SIZE); //receive data, max number of bytes = BUFFER_SIZE

    //the first signal is of type long, therefore 4 bytes
    signal0 = buffer[0] | buffer[1]<<8 | buffer[2]<<16 | buffer[3]<<24;
    dat0 = buffer[0]; //publishing received data (for debugging)
    dat1 = buffer[1]; //publishing received data (for debugging)
    dat2 = buffer[2]; //publishing received data (for debugging)
    dat3 = buffer[3]; //publishing received data (for debugging)
    
    //the second signal is binary, therefore 1 byte
    signal1 = buffer[4];
    
    //the third signal is of type double, therefore 8 bytes
    convData[0] = buffer[5] | buffer[6]<<8 | buffer[7]<<16 | buffer[8]<<24;
    convData[1] = buffer[9] | buffer[10]<<8 | buffer[11]<<16 | buffer[12]<<24;
    signal2 = LongAsDouble(convData);
    
    //the fourth signal is of type double, therefore 8 bytes
    convData[0] = buffer[13] | buffer[14]<<8 | buffer[15]<<16 | buffer[16]<<24;
    convData[1] = buffer[17] | buffer[18]<<8 | buffer[19]<<16 | buffer[20]<<24;
    signal3 = LongAsDouble(convData);
  }  
  
  //publishing the serial communication handle through output signal (for debugging)
  handle = hCom;
  //and also the number of received bytes
  receivedBytes = dataCnt;
  return 0;
}

/* Closing the REXLANG algorithm */
//the exit procedure is executed once when the task is correctly terminated
// (system shutdown, downloading new control algorithm, etc.)
long exit(void)
{
	if(hCom>=0) Close(hCom);
  return 0;
}

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#1 2016-01-07 13:05:09