ESP8266 Community Forum

- Wed Nov 08, 2017 12:15 am #71628 Hello guys. I have spent some days trying to connect two boards wemos d1 mini via i2c. I cant understand what i'm doing wrong, but it does not work. When i scan on master i dont find any slave. Result code on Wire.endTransmission is always = 2. I connect both of them using USB to my PC, D1 -> D1, D2 -> D2, GND -> GND. Iam so stupid, so I dont understand why to share ground, but I do so, because I saw it in a few examples
And it's not clear for me whether to use pull up resostors or not - I can't understand if my PINS already have it.

Here's some code snippet:

Code: Select all// Master

void I2CMaster::setup()
{
    Wire.begin();
}

void I2CMaster::loop()
{
    Wire.beginTransmission(100);
    Wire.write('c');
    byte error = Wire.endTransmission();

    _logger->println(error); // always 2!
}


Code: Select all// Slave

void onReceive(int numBytes)
{
    // Never called
    while(Wire.available() > 0){
        int read = Wire.read();

        Serial.println(read);
    }
}

void setup()
{
    Wire.begin(100);
    Wire.onReceive(onReceive);
}


Thank you!