I am trying to read from these sensors but only 1 sensor's reading is coming on the serial monitor on sending the 'R' character. the code is `#include //enable I2C.

define address 97 //default I2C ID number for EZO D.O. Circuit.

define address_pH 99 //default I2C ID number for EZO pH Circuit.

char computerdata[20]; //we make a 20 byte character array to hold incoming data from a pc/mac/other. byte received_from_computer = 0; //we need to know how many characters have been received. byte code = 0; //used to hold the I2C response code. char DO_data[20]; //we make a 20 byte character array to hold incoming data from the D.O. circuit. byte inchar = 0; //used as a 1 byte buffer to store inbound bytes from the D.O. Circuit. int time = 900; //used to change the delay needed depending on the command sent to the EZO Class D.O. Circuit. float DO_float; //float var used to hold the float value of the DO. char DO; //char pointer used in string parsing. char sat; //char pointer used in string parsing. float do_float; //float var used to hold the float value of the dissolved oxygen. float sat_float; //float var used to hold the float value of the saturation percentage.

char computerdata_pH[20]; //we make a 20 byte character array to hold incoming data from a pc/mac/other. byte received_from_computer_pH = 0; //we need to know how many characters have been received. byte code_pH = 0; //used to hold the I2C response code_pH. char pH_data[20]; //we make a 20-byte character array to hold incoming data from the pH circuit. byte in_char_pH = 0; //used as a 1 byte buffer to store inbound bytes from the pH Circuit. byte i = 0; //counter used for ph_data array. int time_pH = 900; //used to change the delay needed depending on the command sent to the EZO Class pH Circuit. float ph_float; //float var used to hold the float value of the pH.

void setup() //hardware initialization. { Serial.begin(9600); //enable serial port. Wire.begin(); //enable I2C port. }

void loop() { //the main loop. byte i = 0; //counter used for DO_data array.

if (Serial.available() > 0) { //if data is holding in the serial buffer received_from_computer = Serial.readBytesUntil(13, computerdata, 20); //we read the data sent from the serial monitor(pc/mac/other) until we see a . We also count how many characters have been received. computerdata[received_fromcomputer] = 0; //stop the buffer from transmitting leftovers or garbage. / computerdata[0] = tolower(computerdata[0]); //we make sure the first char in the string is lower case./ if (computerdata[0] == 'c' || computerdata[0] == 'r')time = 900; //if a command has been sent to calibrate or take a reading we wait 600ms so that the circuit has time to take the reading. else time_ = 300; //if not 300ms will do

Wire.beginTransmission(address);                                      //call the circuit by its ID number.

Wire.write(computerdata);                                             //transmit the command that was sent through the serial port.

   if (strcmp(computerdata, "sleep") != 0) {  //if the command that has been sent is NOT the sleep command, wait the correct amount of time and request data.
  //if it is the sleep command, we do nothing. Issuing a sleep command and then requesting data will wake the D.O. circuit.

  delay(time_);                     //wait the correct amount of time for the circuit to complete its instruction.

  Wire.requestFrom(address, 20, 1); //call the circuit and request 20 bytes (this may be more than we need)

  code = Wire.read();               //the first byte is the response code, we read this separately.

  switch (code) {                   //switch case based on what the response code is.
    case 1:                         //decimal 1.
      Serial.println("Success");    //means the command was successful.
      break;                        //exits the switch case.

    case 2:                         //decimal 2.
      Serial.println("Failed");     //means the command has failed.
      break;                        //exits the switch case.

    case 254:                      //decimal 254.
      Serial.println("Pending");   //means the command has not yet been finished calculating.
      break;                       //exits the switch case.

    case 255:                      //decimal 255.
      Serial.println("No Data from do");   //means there is no further data to send.
      break;                       //exits the switch case.
  }
}
while (Wire.available()) {       //are there bytes to receive.
  in_char = Wire.read();         //receive a byte.
  DO_data[i] = in_char;          //load this byte into our array.
  i += 1;
  if (in_char == 0 || in_char_pH == 0) {            //if we see that we have been sent a null command.
    i = 0;                       //reset the counter i to 0.
    Wire.endTransmission();      //end the I2C data transmission.
    break;                       //exit the while loop.
    Serial.println(DO_data);
    delay(100);
    Wire.beginTransmission(address_pH);                                      //call the circuit by its ID number.
    Wire.write(computerdata_pH);                                             //transmit the command that was sent through the serial port.
    Wire.endTransmission();                                               //end the I2C data transmission.
    if (isDigit(DO_data[0])) {
      string_pars();                  //If the first char is a number we know it is a DO reading, lets parse the DO reading
    }
    else {                            //if it’s not a number
      Serial.println(DO_data);        //print the data.
      for (i = 0; i < 20; i++) {      //step through each char
        DO_data[i] = 0;               //set each one to 0 this clears the memory
      }
    }

    if (strcmp(computerdata_pH, "sleep") != 0) {  //if the command that has been sent is NOT the sleep command, wait the correct amount of time and request data.
      //if it is the sleep command, we do nothing. Issuing a sleep command and then requesting data will wake the D.O. circuit.
    }
  }
}

}

   if (Serial.available() > 0) {                                           //if data is holding in the serial buffer
received_from_computer = Serial.readBytesUntil(13, computerdata, 20); //we read the data sent from the serial monitor(pc/mac/other) until we see a <CR>. We also count how many characters have been received.
computerdata[received_from_computer] = 0;                             //stop the buffer from transmitting leftovers or garbage.
/* computerdata[0] = tolower(computerdata[0]);                           //we make sure the first char in the string is lower case.*/
if (computerdata[0] == 'c' || computerdata[0] == 'r')time_ = 900;     //if a command has been sent to calibrate or take a reading we wait 600ms so that the circuit has time to take the reading.
else time_ = 300;                                                     //if not 300ms will do

Wire.beginTransmission(address);                                      //call the circuit by its ID number.

Wire.write(computerdata);                                             //transmit the command that was sent through the serial port.

   delay(time_pH);                     //wait the correct amount of time for the circuit to complete its instruction.

   Wire.requestFrom(address_pH, 20, 1); //call the circuit and request 20 bytes (this may be more than we need)
      code_pH = Wire.read();               //the first byte is the response code, we read this separately.
      switch (code_pH) {                  //switch case based on what the response code is.
        case 1:                         //decimal 1.
          Serial.println("Success");    //means the command was successful.
          break;                        //exits the switch case.

        case 2:                         //decimal 2.
          Serial.println("Failed");     //means the command has failed.
          break;                        //exits the switch case.

        case 254:                      //decimal 254.
          Serial.println("Pending");   //means the command has not yet been finished calculating.
          break;                       //exits the switch case.

        case 255:                      //decimal 255.
          Serial.println("No Data from pH");   //means there is no further data to send.
          break;                       //exits the switch case.

      }

  while (Wire.available()) {         //are there bytes to receive.
  in_char_pH = Wire.read();           //receive a byte.
  pH_data[i] = in_char_pH;            //load this byte into our array.
  i += 1;                          //incur the counter for the array element.
  if (in_char_pH == 0) {              //if we see that we have been sent a null command.
    i = 0;                         //reset the counter i to 0.
    Wire.endTransmission();        //end the I2C data transmission.
    break;                         //exit the while loop.
  }
}
     Serial.println(pH_data);          //print the data.
    }

} void string_pars() { //this function will break up the CSV string into its 2 individual parts, DO and %sat. byte flag = 0; //this is used to indicate is a “,” was found in the string array byte i = 0; //counter used for DO_data array.

for (i = 0; i < 20; i++) {          //Step through each char
  if (DO_data[i] == ',') {          //do we see a ','
    flag = 1;                       //if so we set the var flag to 1 by doing this we can identify if the string being sent from the DO circuit is a CSV string containing tow values
  }
}

if (flag != 1) {                    //if we see the there WAS NOT a ‘,’ in the string array
  Serial.print("DO:");              //print the identifier
  Serial.println(DO_data);          //print the reading
}

if (flag == 1) {                    //if we see the there was a ‘,’ in the string array
  DO = strtok(DO_data, ",");        //let's pars the string at each comma
  sat = strtok(NULL, ",");          //let's pars the string at each comma
  Serial.print("DO:");              //print the identifier
  Serial.println(DO);               //print the reading
  Serial.print("Sat:");             //print the identifier
  Serial.println(sat);              //print the reading
  flag = 0;                         //reset the flag
}

/*                                //uncomment this section if you want to take the ASCII values and convert them into a floating point number.
  DO_float=atof(DO);
  sat_float=atof(sat);
*/

}` only 1 sensor ,dissolved oxygen sensor is able to respond as can also be seen on the green led blink on the sensor. can you please help on this issue.?

pololu / vl53l0x-arduino

Reading from pH sensor and dissolved oxygen sensor on same i2c bus #23

define address 97 //default I2C ID number for EZO D.O. Circuit.

define address_pH 99 //default I2C ID number for EZO pH Circuit.