Hello I'm trying to connect two seeed XIAO SAMD21 with I2C. One would be the master and the other the slave. I came across this github with Wire library examples on how to do it for the SAMD21 CPU's: GitHub - arduino/ArduinoCore-samd: Arduino Core for SAMD21 CPU master Arduino Core for SAMD21 CPU. Contribute to arduino/ArduinoCore-samd development by creating an account on GitHub. I programmed one XIAO with master code: // Wire Master Writer // by Nicholas Zambetti // Demonstrates use of the Wire library // Writes data to an I2C/TWI slave device // Refer to the "Wire Slave Receiver" example for use with this // Created 29 March 2006 // This example code is in the public domain. #include void setup() { Wire.begin(); // join i2c bus (address optional for master) } byte x = 0; void loop() { Wire.beginTransmission(4); // transmit to device #4 Wire.write("x is "); // sends five bytes Wire.write(x); // sends one byte Wire.endTransmission(); // stop transmitting x++; delay(500); } And one as slave: // Wire Slave Receiver // by Nicholas Zambetti // Demonstrates use of the Wire library // Receives data as an I2C/TWI slave device // Refer to the "Wire Master Writer" example for use with this // Created 29 March 2006 // This example code is in the public domain. #include void setup() { Wire.begin(4); // join i2c bus with address #4 Wire.onReceive(receiveEvent); // register event Serial.begin(9600); // start serial for output } void loop() { delay(100); } // function that executes whenever data is received from master // this function is registered as an event, see setup() void receiveEvent(int howMany) { while(1 < Wire.available()) // loop through all but the last { char c = Wire.read(); // receive byte as a character Serial.print(c); // print the character } int x = Wire.read(); // receive byte as an integer Serial.println(x); // print the integer } The slave should receive data from master and print on the serial one character, but nothing happens, Would you be able to help me pinpoint where the error might be?

All looks good. Let's see if the master can find the slave. Download this scanner sketch to the master. Make sure the slave is running before you start the master. The master should find slave a address 4 #include void setup() { Wire.begin(); Serial.begin(9600); Serial.println("\nI2C Scanner"); } void loop() { int nDevices = 0; Serial.println("Scanning..."); for (byte address = 1; address < 127; ++address) { // The i2c_scanner uses the return value of // the Wire.endTransmission to see if // a device did acknowledge to the address. Wire.beginTransmission(address); byte error = Wire.endTransmission(); if (error == 0) { Serial.print("I2C device found at address 0x"); if (address < 16) { Serial.print("0"); } Serial.print(address, HEX); Serial.println(" !"); ++nDevices; } else if (error == 4) { Serial.print("Unknown error at address 0x"); if (address < 16) { Serial.print("0"); } Serial.println(address, HEX); } } if (nDevices == 0) { Serial.println("No I2C devices found\n"); } else { Serial.println("done\n"); } delay(5000); // Wait 5 seconds for next scan }

XIAO SAMD21 I2C master/slave

Projects Programming

jim-p September 13, 2024, 12:36pm 21

Glad you got it to work.
Have a nice day!

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XIAO SAMD21 I2C master/slave

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