arduino-esp32/libraries/Wire/examples/WireMaster/WireMaster.ino

#include "Wire.h"

#define I2C_DEV_ADDR 0x55

uint32_t i = 0;

void setup() {
  Serial.begin(115200);
  Serial.setDebugOutput(true);
  Wire.begin();
}

void loop() {
  delay(5000);

  //Write message to the slave
  Wire.beginTransmission(I2C_DEV_ADDR);
  Wire.printf("Hello World! %u", i++);
  uint8_t error = Wire.endTransmission(true);
  Serial.printf("endTransmission: %u\n", error);
  
  //Read 16 bytes from the slave
  error = Wire.requestFrom(I2C_DEV_ADDR, 16);
  Serial.printf("requestFrom: %u\n", error);
  if(error){
    uint8_t temp[error];
    Wire.readBytes(temp, error);
    log_print_buf(temp, error);
  }
}