Change values of timer using I2C

Question

I'd like to alter the "LED_T_ON" values using an I2C enabled device (i.e. RPi)

Code for Arduino Mega slave:

//slave
#include <Wire.h>
#define SLAVE_ADDRESS 0x08
const int PWR_LED = 43;
int LED_TinH_ON = 18;
int LED_T_ON = 5000;
int LED_T_OFF = 5000;
String inString = ""; // string to hold input
byte LastMasterCommand = 0;
int Mval;
char user_input;
class Relay {
 int relayPin;
 long OnTime; // milliseconds of on-time
 long OffTime; // milliseconds of off-time
 // These maintain the current state
 int relayState; // pumpState used to set the PUMP
 unsigned long previousMillis; // will store last time PUMP was updated
 // Constructor - creates a Timer and initializes the member variables and state
 public:
 Relay(int pin, long on, long off)
 {
 relayPin = pin;
 pinMode(relayPin, OUTPUT); 
 OnTime = on;
 OffTime = off;
 relayState = LOW; 
 previousMillis = 0; //ORIGINALLY 0
 }
 void Update()
 {
 // check to see if it's time to change the state of the TIMER
 unsigned long currentMillis = millis();
 if((relayState == HIGH) && (currentMillis - previousMillis >= OnTime))
 {
 relayState = LOW; // Turn it off
 previousMillis = currentMillis; // Remember the time
 digitalWrite(relayPin, relayState); // Update the actual LED
 }
 else if ((relayState == LOW) && (currentMillis - previousMillis >= OffTime))
 {
 relayState = HIGH; // turn it on
 previousMillis = currentMillis; // Remember the time
 digitalWrite(relayPin, relayState); // Update the actual RELAY
 }
 }
};
Relay relay3(PWR_LED, LED_T_OFF, LED_T_ON);
void setup() {
 // initialize serial communication with computer:
 Serial.begin(9600);
 Wire.begin(SLAVE_ADDRESS);
 Wire.onReceive(receiveData);
 Wire.onRequest(slavesRespond);
 pinMode(PWR_LED, OUTPUT);
}
void loop() {
 delay(1000);
 Serial.print("LED_T_ON=");
 Serial.println(LED_T_ON);
 Serial.print("LED_T_OFF=");
 Serial.println(LED_T_OFF);
 Serial.println();
 relay3.Update();
 switch (Mval) {
 case 1 ... 25:
 LED_TinH_ON = Mval;
 Serial.print("LED time on: ");
 Serial.print(LED_TinH_ON);
 Serial.println("h");
 LED_T_ON = LED_TinH_ON*1000;//*60*60;
 LED_T_OFF = (24-LED_TinH_ON)*1000;//*60*60;
 break;
 }
}
void receiveData(int byteCount) {
 LastMasterCommand = Wire.read();
 while (Wire.available()) {
 int msg = Wire.read();
 if (isDigit(msg)) {
 inString += (char)msg;
 }
 }
 Mval = inString.toInt();
 //Serial.println(LastMasterCommand);
 inString = "";
 //Serial.println(Mval);
}
void slavesRespond() {
}

When I change the value on the RPi the Arduino receives and displays the correct value but the timed relays don't actually use the updated values.

Am I missing something?

• Majenko: I see nothing there relating to I2C. What there can be "displaying the correct value" when there is neither anything receiving a value nor anything displaying anything anywhere?
• Nick Gammon: Same. Also LED_T_ON is not changed anywhere (nor is OnTime).
• Yousef Abdelsalam: My bad, edited to display the right code
• Chad G: assuming maybe you have other code that is doing the I2C bit, if that code is changing the value of LED_T_ON that will have no effect on that relay object as that value is passed in during the construction. You would need to update relay3.OnTime ( your order/naming is also switched, relay3(PWR_LED, LED_T_OFF, LED_T_ON); calls Relay(int pin, long on, long off)

Answer 1

Your updating LED_T_ON and LED_T_OFF but those values were already passed into the constructor and changing them will not change the object. you need to update relay3.OnTime and relay3.OffTime