Converting the number after another number into a 2 algarisms number? (1 then 1 = 11) - Arduino

Question

So, I'm trying to set up a kind of calculator with Arduino. I've already managed to read the data from an IR Remote Control and display them in a LCD 16x2 Display. If I type "1", for example, "1" will be showed on the display, but how do I manage to make the program understand that if two, or more numbers were pressed before the Enter button it's a number with more than 1 algarism? Like pressing 1, then 2 and then 3 is equal to one hundred and twenty three?

I could make a LOT of if statements to do something like "if 1 was pressed after an existing 1 than variable == 11" and so on, but that's not useful.

Anyway, how can I do this? Or can you point me towards the name of this kind of function/algorithm so I can look forward to it.

Thanks.

Answer 1

Here are two ways to go about this. 1st will simply concatenate a string type and convert it to integer when finished by Carriage Return.

#define _CR 13
String readString;

void setup() {
  Serial.begin(9600);
}

void loop() {
  while (Serial.available()) {
    char c = Serial.read();  //gets one byte from serial buffer
    readString += c; //makes the string readString
    delay(2);  //slow looping to allow buffer to fill with next character
  }

  if ((readString.length() >0) || ( c == CR_)) {
    Serial.println(readString);  //so you can see the captured string 
    int n = readString.toInt();  //convert readString into a number

    // do whatever you want
    // ...
    //
    //

    readString=""; //empty for next input
  } 
}

---

The other way is by using an Inter Character Timeout. Note that normally

while (!Serial.available()) {
  // wait for Serial input
};
inkey = Serial.read();

is blocking. The below uses pointers of char array to build up the input, up to 5 digits the length of an int16_t (i.e. 65535). hmm it only deals with positives. But you can tweak it to get negatives, and other commands such as "+", "-", etc...

The reason I use the ICT method, is because the Arduino's IDE Serial Monitor utility defaults to No LF/CR. which just sends the input at once without any LF/CR.

int16_t last_ms_char; // milliseconds of last recieved character from Serial port.
int8_t buffer_pos; // next position to recieve character from Serial port.
char buffer[6]; // 0-35K+null
int16_t fn_index;
int16_t Serial_Input_Number;

void setup() {

  Serial.begin(115200);
  last_ms_char = millis(); // stroke the inter character timeout.
  buffer_pos = 0; // start the command string at zero length.

}

void loop() {

  char inByte;
  if (Serial.available() > 0) {
    inByte = Serial.read();
    if (isDigit(inByte)) { // macro for ((inByte >= '0') && (inByte <= '9'))
      // else if it is a number, add it to the string
      buffer[buffer_pos++] = inByte;
    } else {
      // input char is a letter command
      buffer_pos = 0;
      parse_menu(inByte);
    }
    buffer[buffer_pos] = 0; // update end of line
    last_ms_char = millis(); // stroke the inter character timeout.

  } else if ((millis() - last_ms_char) > 500 && ( buffer_pos > 0 )) {
    // ICT expired and have something
    if (buffer_pos == 1) {
      // look for single byte (non-number) menu commands
      parse_menu(buffer[buffer_pos - 1]);

    } else if (buffer_pos > 5) {
      // dump if entered command is greater then uint16_t
      Serial.println(F("Ignored, Number is Too Big!"));

    } else {
      // otherwise its a number, scan through files looking for matching index.
      Serial_Input_Number = atoi(buffer);

      //
      //
      // Do something with "Serial_Input_Number"
      // one time here. Or set flag and do something out of this big if
      // ...
      //
      //


    }

    //reset buffer to start over
    buffer_pos = 0;
    buffer[buffer_pos] = 0; // delimit

    //
    //
    // do other stuff repeatedly between new characters
    // ...
    //
    //
  }

No guarantee on the exact code as it was sniped and trimmed from larger examples, that do work.