control servo using android

Question

Asked question master, how to coding in arduino for controlling servo using android via bluetooth? Code below does not work, servo only runs between 48 - 56.

#include <SoftwareSerial.h> #include <SoftwareSerial.h> #include <Servo.h> Servo servo; int bluetoothTx = 10; int bluetoothRx = 11; SoftwareSerial bluetooth(bluetoothTx, bluetoothRx); void setup() {   servo.attach(9);
 Serial.begin(9600); bluetooth.begin(9600);} void loop() {
//read from bluetooth and wrtite to usb serial
if(bluetooth.available()> 0 ){    int servopos = bluetooth.read();
Serial.println(servopos);
servo.write(servopos);}} 

Answer 1

1. Read the data as string using: string input = bluetooth.readString();
2. Then convert string to int using: int servopos = int(input);
3. Then write the position to the servo:servo.write(servopos);

Now depending on the data you send from android, you could need to :
Trim it: input = input.trim();
Or constrain it : servopos = constrain(servopos,0,180);

Your corrected code:

#include <SoftwareSerial.h>
#include <Servo.h>
Servo servo;
int bluetoothTx = 10;
int bluetoothRx = 11;
SoftwareSerial bluetooth(bluetoothTx, bluetoothRx);
void setup() {
  servo.attach(9);
  Serial.begin(9600);
  bluetooth.begin(9600);
} 

void loop() {
  //read from bluetooth and wrtite to usb serial
  if (bluetooth.available() > 0 ) {
    String s = bluetooth.readString();
    s.trim();
    float servopos = s.toFloat();
    servopos = constrain(servopos, 0, 180);
    Serial.println("Angle: "+String(servopos));
    servo.write(servopos);
  }
}

Answer 2

What you are reading from the bluetooth is coming in as individual bytes of ascii code. The ascii codes for digits run from 48 to 57. So if you send for example "10" then it sends a 49 and then a 48. You are just reading the values directly. Instead you need to accumulate the characters you read into a buffer until you have them all and then use atoi to convert to a real number you can use.