Change servo angle based on Bluetooth input

Question

I'm using an app to either turn on an LED or change the angle of a micro servo depending on which button is pressed (using Arduino). My code works for the LED (while the button is pressed, the LED is on) but nothing happens when I press the button meant to change the angle of the servo to 40.

// Bluetooth serial:
#include <SoftwareSerial.h> // import the serial library

// setup the bluetooth coms
SoftwareSerial BTSerial(8,7);

#include <Servo.h>

int servoPin = 0;

Servo servo;

int angle = 0; // servo position in degrees
int input = 0;
int led2 = 13;

void setup() {
  // put your setup code here, to run once:
  servo.attach(servoPin);
  Serial.begin(9600);   // coms w/ computer
  BTSerial.begin(9600); // coms w/ Bluetooth
  pinMode(led2, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:

  if (BTSerial.available())
  {
    input = BTSerial.read();
    digitalWrite(led2, LOW);

    switch(input) {
      case 'E':
        angle = 40;
        break;

      case 'C':
        digitalWrite(led2, HIGH);
        break;
    }

    servo.write(angle);
  }
}

The input is right as I checked by also turning the LED on in case 'E' where it worked as normal. I had also tried using servo.write() within the case function as well but this didn't work either.

case 'E':
   servo.write(40);
   break;

There's no error message, the servo just doesn't move at all — user9049016, Dec 04 '17 at 05:11
Yes I did servo.attach, I tried Servo::refresh(); but it gave the error: 'refresh' is not a member of 'Servo'. — user9049016, Dec 04 '17 at 05:30
Which pin did you attach it to? Edit your question to show a [complete example](https://stackoverflow.com/help/mcve). — aaron, Dec 04 '17 at 05:36
Changing the pin worked thank you! I'm wondering why the pin matters though? I thought all pins were the same (i'm using Arduino UNO) — user9049016, Dec 04 '17 at 05:59
I'm guessing that the Arduino is connected to your computer through USB? — aaron, Dec 04 '17 at 06:05

score 0 · Accepted Answer · answered Dec 04 '17 at 06:12

You cannot use digital pins 0 or 1 as input:

As mentioned, those are serial send and receive pins. If you power your computer through USB, it can interfere if you try to use them, since it's reading from both the USB to Serial and the pin. Also you have an issue with anything connected (well, not anything, but remove it just to be safe) when you're trying to program. If you use the pins as intended, and program then run it off battery, it should be no problem at all.

Most of us stay away from it because it's a bit of a hassle

Depending on your Arduino model, servo.attach only supports pins 9 and 10:

Note that in Arduino 0016 and earlier, the Servo library supports only servos on only two pins: 9 and 10.

Or you could just use one of those anyway.

Change servo angle based on Bluetooth input

1 Answers1