PeripheralReceiver.ino

Makes the board an I2C peripheral at address 0x42. Prints the bytes a controller writes, and answers each read with a counter that goes up by one.

Uses PhyduinoWire::begin(uint8_t) with PhyduinoWire::onReceive() and PhyduinoWire::onRequest().

Wiring

SDA, SCL and GND to another board running a controller sketch.

Output

Serial Monitor at 115200 baud: the bytes the controller wrote, as text.

Note

The callbacks run inside the I2C interrupt, so keep them short.

// I2C peripheral at address 0x42: prints bytes a controller writes, and answers
// read requests with a counter. Pair with another board running a controller sketch.
#include <Wire.h>
 
volatile uint8_t counter = 0;
 
void onReceive(int count) {
    (void)count;
    while (Wire.available()) {
        Serial.write(Wire.read());
    }
}
 
void onRequest() {
    Wire.write(counter++);
}
 
void setup() {
    Serial.begin(115200);
    Wire.onReceive(onReceive);
    Wire.onRequest(onRequest);
    Wire.begin(0x42);
}
 
void loop() {}