A better strategy to separate incoming serial messages?

heya, thanks for getting back so quickly - I found your reply very useful!

I'm attaching the Arduino code at the end; the sensors are apds9960 colour & gesture sensors (atm I'm only using the colour).

If you don't need other color values, that could speed up the whole process of reading sensors and sending values which could at the end be sent as list of 24 values.

uff yeah, so obvious, but really didn't think of that.

Usual way is to try to send a value only if it changed, to avoid unneeded strain on serial port.

One could also downscale 12bit 0-4095 to 8bit 0-255 in Arduino,
before sending the data.

how would I do that?

All I need to know is if all 24 sensors send 1 long list, or if each sensor sends separately

the sensors send the values separately, not as a list.

here's the Arduino code:

/**/

#include<Wire.h>
#include "Adafruit_APDS9960.h" /*include libraries*/

/***********************************************************************************************************************************************************************************************************************************************************/

// declarations

Adafruit_APDS9960 apds[24]; /*initialize sensor*/

byte tcaI2CAddress[] = {0x70, 0x71, 0x72, 0x73}; /*define array containing all the addresses*/
byte numberOfTCAs = 4; /* define number of TCAs used */
byte numberOfDevicesPerTCA = 6; /* define number of Sensors per TCA */
const int numberOfDevices = 24; /* define number of total devices */

/***********************************************************************************************************************************************************************************************************************************************************/

void setup() {
  Wire.begin();
  Serial.begin(115200); /*begin serial communication (Arduino -> PC) at 115200 Baud rate*/

  // 0. run i2c scanner
  Serial.println("I2C Scanner ready!");
  Serial.println();
  scanI2C(400000); /*run i2c scanner function*/
  Serial.println("-------------------------------");
  Serial.println();

  // 1. switch off all TCAs
  for (int i = 0; i < numberOfTCAs; i++){
  Wire.beginTransmission(tcaI2CAddress[i]);
  Wire.write(0);
  Wire.endTransmission(); 
  }

  // 2. initialize sensors
  for (int i = 0; i < numberOfDevices; i++){

    byte tca = setTCAAndChannel(i);

    Serial.print("Initializing APDS_");
    Serial.println(i);
    Serial.println();
    
  if(!apds[i].begin()){ /*if function returns 0, print "failed to initialize...", else print "initialized!"*/
    Serial.println("failed to initialize device! Please check your wiring.");
    Serial.println();
  }
  else {Serial.println("Device initialized!");
  Serial.println();
  }
  
  apds[i].enableColor(true); /*enable color sensing mode*/

  // 3. close TCA
  closeTCA(tca);
  }
  
}

void loop() { 

  // 1. switch off all TCAs
  for (int i = 0; i < numberOfTCAs; i++){
  Wire.beginTransmission(tcaI2CAddress[i]);
  Wire.write(0);
  Wire.endTransmission(); 
  }

  // 2. run color readings

  for (int i = 0; i < numberOfDevices; i++){

  byte tca = setTCAAndChannel(i);
    
  uint16_t r, g, b, c; /*create some variables to store the color data in*/

  while(!apds[i].colorDataReady()){ /*wait for color data to be ready*/
    delay(1); /*Adafruit: 5; THIS DELAY ALONE AMOUNTS TO 125 ms !!!!!*/
  }

  apds[i].getColorData(&r, &g, &b, &c); /*get the data and print the different channels*/

  Serial.print("Red_");
  Serial.print(i);
  Serial.print(": ");
  Serial.print(r);
  Serial.print(" Green_");
  Serial.print(i);
  Serial.print(": ");
  Serial.print(g);
  Serial.print(" Blue_");
  Serial.print(i);
  Serial.print(": ");
  Serial.print(b);
  Serial.print(" Clear_");
  Serial.print(i);
  Serial.print(": ");
  Serial.println(c);
  Serial.println();

  // 3. close TCA
  closeTCA(tca);
  }
  Serial.println("****************************");  
  delay(1);
}

/**************************************************************************************************************************************************************************************************************************************************************/

byte setTCAAndChannel(byte i){ /* define function for setting TCA and sensor */
  byte tca = i/numberOfDevicesPerTCA; /* divide i (total # of devices) by # of TCAs, that way because it's int, 1,5 will still be 1, thereby selecting the correct TCA */
  byte channel = i%numberOfDevicesPerTCA; /* modulo... divide i (the total number of devices) by the # of devices per TCA and give the rest, e.g. 2%4 = 0*/

  Wire.beginTransmission(tcaI2CAddress[tca]);
  Wire.write(1 << channel);
  Wire.endTransmission(); 

  // Serial.print("Calculation: ");
  // Serial.print(i);
  // Serial.print(" / ");
  // Serial.print(numberOfTCAs);
  // Serial.print(" = ");
  
  Serial.print("TCA: ");
  Serial.println(tca);
  
  Serial.print("Channel: ");
  Serial.println(channel);
   
  return tca; 
}

void closeTCA(byte tca){
  Wire.beginTransmission(tcaI2CAddress[tca]);
  Wire.write(0);
  Wire.endTransmission(); 
  }
  
void scanI2C(long frequency){
  
  String normal = "standard mode (100 kHz):";
  String fast = "fast mode (400 kHz):";
  String defaultStr = " !!!!! Unzulässige Frequenz !!!!!";
  
  bool error = true;
  bool addressFound = false;
  
  Serial.print("Scanne im ");
  switch(frequency){ /* switch...case is similar to an if...then statement */
    case 100000:
      Serial.println(normal); /*print string "standard mode (100kHz)", previously defined as 'normal'*/
      break;
    case 400000:
      Serial.println(fast); /*print string "fast mode (400kHz)", previously defined as 'fast'*/
      break; /*ends the switch...case statement*/
  }
  
  Wire.setClock(frequency);
  for(int i=1; i<128; i++){
    Wire.beginTransmission(i); /*begins transmission on the specified address i, e.g. 127*/
    error = Wire.endTransmission(); /*Wire.endTransmission() returns bytes for status of transmission: 0 = success, 1 = data too long, ... 4 = other ; here "error" is set to 0 or "false" if Wire.endTransmission() returns 0 (= transmssion successful) and "true" for everything else (1 - 4)*/
    if(error == 0){ /*if the "error" Boolean is set to "false" (meaning the transmission was successful), proceed by ... */
      addressFound = true; /*setting "addressFound" to true*/
      Serial.print("0x"); /*prints the address of the i2c device from two components, first "0x" ... */
      Serial.println(i,HEX); /* ... and second the number where a device was found as HEX, i.e. 127 = 7F, totalling 0x7F*/
    }
  }
  if(!addressFound){ /*if no address was found for all 128 addresses, print: */
    Serial.println("Keine Adresse erkannt");
  }
  Serial.println();
}