James,
I just sent you an email regarding this, but I figured I would post here in case anyone else runs into this problem. The library was written which a single sensor in mind. it opens up a software serial port so to use multiple instances of it would require you to switch between them. However these sensors use a modbus protocol so they can be addressed, so you can talk to several of them on a single Serialport . The default address is 104 (0x68), so change one of the sensors adresses and then you can read from them independently. The following code has a function that will change the address of the attached sensor to 0x34. connect ONLY ONE sensor to the arduino and uncomment the line "//changeAddress();", then run the program. then comment out or delete that line and upload it again. now you can attach both sensors to the same Tx/Rx (12,13) and it will read from both of them.
/*
Basic Arduino example for K-Series sensor
Created by Jason Berger
*edited to use 2 sensors on the same line*
Co2meter.com
*/
#include "SoftwareSerial.h"
byte addressA = 0x68;
byte addressB = 0x34; //change to address
SoftwareSerial K_30_Serial(12,13); //Sets up a virtual serial port
//Using pin 12 for Rx and pin 13 for Tx
byte readCO2_a[] = {addressA, 0X44, 0X00, 0X08, 0X02, 0X9F, 0X25}; //Command packet to read Co2 (see app note)
byte readCO2_b[] = {addressB, 0X44, 0X00, 0X08, 0X02, 0X9F, 0X25};
byte response[] = {0,0,0,0,0,0,0}; //create an array to store the response
unsigned long valCO2_A;
unsigned long valCO2_B;
//multiplier for value. default is 1. set to 3 for K-30 3% and 10 for K-33 ICB
int valMultiplier = 1;
void setup()
{
// put your setup code here, to run once:
Serial.begin(9600); //Opens the main serial port to communicate with the computer
K_30_Serial.begin(9600); //Opens the virtual serial port with a baud of 9600
//Uncomment the following line to and run to change address of connected sensor to 0x34;
//This should only be done with one sensor attached
//changeAddress();
}
void loop()
{
sendRequest(readCO2_a); //send request to A and store response
valCO2_A = getValue(response); //parse response and store as valCO2_A
sendRequest(readCO2_b); //send request to B and store response
valCO2_B = getValue(response); //parse response and store as valCO2_A
Serial.print("Co2[A] ppm = ");
Serial.println(valCO2_A);
Serial.print("Co2[B] ppm = ");
Serial.println(valCO2_B);
delay(2000);
}
void sendRequest(byte packet[])
{
while(!K_30_Serial.available()) //keep sending request until we start to get a response
{
K_30_Serial.write(readCO2,7);
delay(50);
}
int timeout=0; //set a timeoute counter
while(K_30_Serial.available() < 7 ) //Wait to get a 7 byte response
{
timeout++;
if(timeout > 10) //if it takes to long there was probably an error
{
while(K_30_Serial.available()) //flush whatever we have
K_30_Serial.read();
break; //exit and try again
}
delay(50);
}
for (int i=0; i < 7; i++)
{
response[i] = K_30_Serial.read();
}
}
unsigned long getValue(byte packet[])
{
int high = packet[3]; //high byte for value is 4th byte in packet in the packet
int low = packet[4]; //low byte for value is 5th byte in the packet
unsigned long val = high*256 + low; //Combine high byte and low byte with this formula to get value
return val* valMultiplier;
}
void changeAddress()
{
//The adress is stored in the eeprom at address 0x00 and RAM address 0x20
//if it is changed in eeprom it will automatically be loaded into ram after a power cycle
//but we will write it manually so we dont have to powercycle
//
//if desired adress is changed then the CRC (last 2 bytes) must be recalculated also
//
byte changeEEPROM[] = {0xFE,0x43,0x00,0x00,0x1,0x34,0x50,0x4d};
byte changeRAM[] = {0xFE,0x41,0x00,0x20,0x1,0x34,0x28,0x47};
K_30_Serial.write(changeEEPROM,8); //Send each one 3 times just to ensure it goes through
delay(100);
K_30_Serial.write(changeEEPROM,8);
delay(100);
K_30_Serial.write(changeEEPROM,8);
delay(100);
K_30_Serial.write(changeRAM,8);
delay(100);
K_30_Serial.write(changeRAM,8);
delay(100);
K_30_Serial.write(changeRAM,8);
delay(100)
}
-Jason B
Co2meter.com
