Conversion of String to integer

Projects Programming
1

I dont understand how the speed value is calculated. I understood why 48 is subtracted but I don't understand the multiplication of 100. Because isnt subtraction of 48 already gives the integer value

</>
#include<SoftwareSerial.h>
SoftwareSerial bt_ser(10,11); //connected to RX and TX pins for serial data communication
char c[6];
int i=0,speed_value=0,send_value;

#define pwm1 9 //input 2
#define pwm2 10 //input 1

boolean motor_dir = 0;

void setup()
{
Serial.begin(9600);
bt_ser.begin(9600);
pinMode(pwm1, OUTPUT);
pinMode(pwm2, OUTPUT);
}

void loop()
{

while(bt_ser.available()) //when data is transmitted
{
if(bt_ser.available()>0)
{
c[i] = bt_ser.read(); //reading the string sent from master device
Serial.print(c[i]);
i++;
}
if(c[i-1]=='N') //if button is pressed
{
motor_dir = !motor_dir; //toggle direction variable
if(motor_dir) //setting direction, pwm1 and pwm2 are opposites
digitalWrite(pwm2, 0);
else
digitalWrite(pwm1, 0);
}
}

   speed_value = (c[1]-48)*100+(c[2]-48)*10+(c[3]-48)*1;  //interpreting speed from string
   if(motor_dir)   //for a given direction
      {
        if(c[i-1]=='*'){   //if data has been transmitted from slider we CHnged the # with *
          
          analogWrite(pwm1, speed_value-100);  //-100 so that when slider is on "0" speed is 0
          i=0;
        }
      }
    else{       //for opposite direction
      if(c[i-1]=='#'){
        
        analogWrite(pwm2, speed_value-100);
        i=0;
      }
      
    }

}
</>

2

Please edit your post to add code tags. Remove the </> characters at each end, then select the code, and press the "</>" post editor button.

Alternatively, replace those </> characters with three back tics `

3

give this a try..

#include<SoftwareSerial.h>
SoftwareSerial bt_ser(10, 11); //connected to RX and TX pins for serial data communication
char c[6];
int i = 0, speed_value = 0, send_value;

#define pwm1 9 //input 2
#define pwm2 10 //input 1

boolean motor_dir = 0;
bool CommandReady = false;
void setup()
{
  Serial.begin(9600);
  Serial.println("Ready");
  bt_ser.begin(9600);
  pinMode(pwm1, OUTPUT);
  pinMode(pwm2, OUTPUT);
}

void loop()
{

  while (bt_ser.available()) //when data is transmitted
    //while (Serial.available()) //use for sim debugging
  {
    char aChar = bt_ser.read();
    // char aChar = Serial.read(); //use for sim debugging

    if (aChar != 10) {
      if (i < sizeof(c)) {
        c[i] = aChar;
        i++;
      }
    } else {
      CommandReady = true;
    }

  }

  if (CommandReady) {
    CommandReady = false;

    if (c[0] == 'N') //if button is pressed
    {
      Serial.println("N Command");
      motor_dir = !motor_dir; //toggle direction variable
      if (motor_dir) //setting direction, pwm1 and pwm2 are opposites
        digitalWrite(pwm2, 0);
      else
        digitalWrite(pwm1, 0);
      i = 0;
    } else
    {
      //try to convert c to int
      speed_value = atoi(c);
      Serial.print("c: ");
      Serial.println(c);
      Serial.print("speed: ");
      Serial.println(speed_value);
      if (motor_dir)  //for a given direction
      {
        if (c[i - 1] == '*') { //if data has been transmitted from slider we CHnged the # with *

          analogWrite(pwm1, speed_value - 100); //-100 so that when slider is on "0" speed is 0
          i = 0;
        }
      }
      else {      //for opposite direction
        if (c[i - 1] == '#') {

          analogWrite(pwm2, speed_value - 100);
          i = 0;
        }

      }
    }
    i = 0;
  }

}

sim here..

have fun.. ~q

4

Welcome

If you have 3 digits 1 2 and 3 and you want a number 123, then you do 1 * 100 + 2 * 10 + 3