Create Callback function for I2C light sensor using Arduino IDE - c

Question

I am trying to create the callback function and display the parameters in the loop function without initializing a global variable.
#include <Wire.h>
#define Addr 0x39
void setup() {
Wire.begin();
Serial.begin(115200);
}
void loop()
{
tmg39931(green, red, blue, cdata, c);
delay(100);
}
void tmg39931(float green, float red, float blue, float cdata, float c){
// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select Enable register
Wire.write(0x80);
// Power ON, ALS enable, Proximity enable, Wait enable
Wire.write(0x0F);
// Stop I2C transmission
Wire.endTransmission();
// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select ADC integration time register
Wire.write(0x81);
// ATIME : 712ms, Max count = 65535 cycles
Wire.write(0x00);
// Stop I2C transmission
Wire.endTransmission();
// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select Wait time register
Wire.write(0x83);
// WTIME : 2.78ms
Wire.write(0xFF);
// Stop I2C transmission
Wire.endTransmission();
// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select control register
Wire.write(0x8F);
// AGAIN is 1x
Wire.write(0x00);
// Stop I2C transmission
Wire.endTransmission();
delay(300);
//Reading the values
unsigned int data[9];
// Start I2C Transmission
Wire.beginTransmission(Addr);
// Select data register
Wire.write(0x94);
// Stop I2C transmission
Wire.endTransmission();
// Request 9 bytes of data
Wire.requestFrom(Addr, 9);
// Read the 9 bytes of data
// cData channel LSB, cData channel MSB, Red channel LSB, Red channel MSB
// Green channel LSB, Green channel MSB, Blue channel LSB, Blue channel MSB, proximity
if(Wire.available() == 9)
{
data[0] = Wire.read();
data[1] = Wire.read();
data[2] = Wire.read();
data[3] = Wire.read();
data[4] = Wire.read();
data[5] = Wire.read();
data[6] = Wire.read();
data[7] = Wire.read();
data[8] = Wire.read();
}
// Convert the data
float cData = data[1] * 256.0 + data[0];
float red = data[3] * 256.0 + data[2];
float green = data[5] * 256.0 + data[4];
float blue = data[7] * 256.0 + data[6];
float c = data[8];
// Output data to serial monitor
// Serial.print("Green Color Luminance : ");
// Serial.println(green);
// Serial.print("Red Color Luminance : ");
// Serial.println(red) ;
// Serial.print("Blue Color Luminance : ");
// Serial.println(blue) ;
// Serial.print("InfraRed Luminance : ");
// Serial.println(cData) ;
// Serial.print("Proximity of the device : ");
// Serial.println(c);
delay(500);
}
}
I am not able to receive my values to loop function due to the wrong implementation of the function.
I need your suggestion to make this kind of solution or any different way which will be useful to make a callback function.

Answer 1

On Arduino it is typical to use global variables for things. You'll be having hard time trying to fight with that.
If you want to get multiple values read from your function, you could define a struct that packs those values, and pass a pointer to that struct as an output parameter, and fill it in your function.
I don't believe that Arduino has callbacks out of the box, but you might implement an event loop yourself.