Example Code for Arduino-URM Sensor and Servo Test

Hardware Preparation

• Cherokey 4WD Robot Kit (SKU: ROB0117)
• RoMeo BLE Microcontroller (SKU: ROB0117)
• URM Ultrasonic Sensor (v3.2 or v4.0)
• 9g Micro Servo
• F-F jumper wires
• 5x AA batteries or 7.5V LiPo battery

Software Preparation

• Arduino IDE (download from https://www.arduino.cc/en/software)
• Metro Library (download from https://www.dfrobot.com.cn/images/upload/File/20141031110246wu4065.rar)
• Installation: Extract the Metro library to the Arduino libraries folder (usually Documents/Arduino/libraries).

Wiring Diagram

URM Sensor to RoMeo BLE connections:

Servo to RoMeo BLE connection:

• Servo Signal: D9
• Servo +5V: +5V (red wire)
• Servo GND: GND (black wire)

Images:

Other Preparation Work

1. Install the Metro library as described.
2. Connect the URM sensor and servo to the RoMeo BLE following the wiring diagram.
3. Ensure the servo is mounted on the Cherokey chassis (follow the instruction manual).
4. Power the Cherokey with batteries or a LiPo battery.

Sample Code

#include <Servo.h>
#include <Metro.h>
Metro measureDistance = Metro(50);
Metro sweepServo = Metro(20);

unsigned long actualDistance = 0;

Servo myservo;  // create servo object to control a servo
int pos = 60;
int sweepFlag = 1;


int URPWM = 3; // PWM Output 0－25000US，Every 50US represent 1cm
int URTRIG= 10; // PWM trigger pin
uint8_t EnPwmCmd[4]={0x44,0x02,0xbb,0x01};    // distance measure command

void setup(){                                 // Serial initialization
  myservo.attach(9);
  Serial.begin(9600);                         // Sets the baud rate to 9600
  SensorSetup();
}

void loop(){
 if(measureDistance.check() == 1){
      actualDistance = MeasureDistance();
//      Serial.println(actualDistance);
//      delay(100);
 }

 if(sweepServo.check() == 1){
      servoSweep();
 }

}

void SensorSetup(){
  pinMode(URTRIG,OUTPUT);                     // A low pull on pin COMP/TRIG
  digitalWrite(URTRIG,HIGH);                  // Set to HIGH
  pinMode(URPWM, INPUT);                      // Sending Enable PWM mode command
  for(int i=0;i<4;i++){
      Serial.write(EnPwmCmd[i]);
   }
}

int MeasureDistance(){        // a low pull on pin COMP/TRIG  triggering a sensor reading
    digitalWrite(URTRIG, LOW);
    digitalWrite(URTRIG, HIGH);               // reading Pin PWM will output pulses
    unsigned long distance=pulseIn(URPWM,LOW);
    if(distance==50000){              // the reading is invalid.
      Serial.print("Invalid");
    }else{
      distance=distance/50;           // every 50us low level stands for 1cm
    }
    return distance;
}

void servoSweep(){
  if(sweepFlag ){
     if(pos>=60 && pos<=120){
        pos=pos+1;                                  // in steps of 1 degree
        myservo.write(pos);                         // tell servo to go to position in variable 'pos'
    }
      if(pos>119)  sweepFlag = false;                       // assign the variable again
  }else {\
      if(pos>=60 && pos<=120){
        pos=pos-1;
        myservo.write(pos);
      }
      if(pos<61)  sweepFlag = true;
   }
}

Note: Uncomment the lines // Serial.println(actualDistance); and // delay(100); to view distance data in the serial monitor.

Result

• The servo sweeps from 60° to 120° and back repeatedly.
• The serial monitor displays distance values (in cm) from the URM sensor (if uncommented).
• Moving an object closer to the sensor decreases the distance value; moving it away increases the value.

Additional Information

• URM Sensor Version Note: The URM v3.2 has a "PWM" pin (pin 4), while the URM v4.0 has an "Echo" pin (pin 4). Both work with the provided wiring.
• Ensure the servo signal wire is connected to D9 (not D4/D7, which are for motor direction).