I2C Issues between Core and Uno [Solved!]

Troubleshooting
13

Everything is working! However, there are a couple of things I had to fix. First, as per timb, I made the Spark the master with this code:

#include "application.h"

#define BUTTON D4

#define OTHER_ADDRESS 0x09

int last_state = HIGH;

void setup() {
  pinMode(BUTTON, INPUT_PULLUP);

  Wire.begin();
}

void loop()
{
    if (digitalRead(BUTTON) != last_state){
        last_state = digitalRead(BUTTON);
        Wire.beginTransmission(OTHER_ADDRESS);
        Wire.write(last_state);
        Wire.endTransmission();
        }
}

The button “bebounce” that BDub suggested was great but that is not what was needed. The original code was looking for a change in the button and would xmit that change to the slave. Also, note I removed the boolean on the last_state and made it an INT since that’s what digitalRead returns.

On the arduino side, I used this code:

#include <Wire.h>

#define LED 3

#define THIS_ADDRESS 0x09

void setup() {
  pinMode(LED, OUTPUT);
  digitalWrite(LED, LOW);

  Wire.begin(THIS_ADDRESS);
  Wire.onReceive(receiveEvent);
}

void loop() {
}

void receiveEvent(int howMany){
  while (Wire.available() > 0){
    uint8_t b = Wire.read();
    digitalWrite(LED, !b);
  }
}

Because I used a 3.3V Arduino pro mini, I put an LED to ground via a resistor on digital pin 3. When I grounded D4 on the Spark, the LED went out. When I let D4 “float”, the LED turned on. :smile: