代码：

 

注意，使用到了SR04的类库。

ApmSonar.ino

// sr04 to apm I2c sonar// by panxu mail: pxzleo@126.com// Created 2014#include 
     
      #include "SR04.h"#define TRIG_PIN 2#define ECHO_PIN 3SR04 sr04 = SR04(ECHO_PIN,TRIG_PIN);uint16_t reading_cm;uint16_t tempread;void setup(){  reading_cm=0;   Wire.begin(0x70);                // join i2c bus with address #2  Wire.onRequest(requestEvent); // register event}void loop(){  tempread=sr04.DistanceAvg(25,1);  if (tempread<500)         reading_cm=tempread;  }void requestEvent(){  byte sendhi;  byte sendli;  byte sendbyte[2];  uint16_t tempreading_cm;  tempreading_cm=reading_cm;  sendhi=tempreading_cm>>8;  sendli=tempreading_cm&0xff;  sendbyte[0]=sendhi;  sendbyte[1]=sendli;  Wire.write(sendbyte,2); }