Switchcase statement issue and Arduino MEGA

This question is from Gary Kahne:

• Arduino Course for Absolute Beginners, 2nd Edition
  • Control Structures
    • Serial Library and Control Function Application

Question:

Here is the code that was giving Gary trouble:

/*This program takes user input from a computer
   through the Arduino IDE serial monitor "send" line.

   The values sent are checked against a switch case
   statement.

   Each case turns on a different LED, or has an effect
   on the LEDs attached to pins on the connected Arduino.
*/

/* these are pins that will be used for the LEDs.
*/
const byte LED_1_Pin = 6;
const byte LED_2_Pin = 7;
const byte LED_3_Pin = 8;
const byte LED_4_Pin = 9;

/*Define start and stop point for "for loops"
   NOTE: these varaible will only be helpful in
   "for loops" if all the pins used are contiguos
   to each other.
*/
const byte firstLEDpin = 6;
const byte lastLEDpin = 9;

void setup() {

  /*Initiate serial comunication for talking between
     the computer and Arduino.
  */
  Serial.begin(9600);

  //Set the mode of the LED pins as OUTPUTS
  for (int i = firstLEDpin; i < lastLEDpin + 1; i++) {
    pinMode(i, OUTPUT);
  }

}

void loop() {

  /* Check to see if there are any bytes available
      in the incoming serial buffer - the user would
      have typed and sent these in the Arduino IDE
      serial monitor "send line".
  */
  if (Serial.available() > 0) {

    /*If there is data available, then read out the
      first byte and assign its value to a variable
    */
    byte userSelection = Serial.read();

    /*Based on the selection of the user
      use a switch case to perfrom a
      specific task
    */
    switch (userSelection) {

      case 'a':
        digitalWrite(LED_1_Pin, HIGH);
        break;

      case 'b':
        digitalWrite(LED_2_Pin, HIGH);
        break;

      case 'c':
        digitalWrite(LED_3_Pin, HIGH);
        break;

      case 'd':
        digitalWrite(LED_4_Pin, HIGH);
        break;

      case 'e':
        for (int i = firstLEDpin; i < lastLEDpin + 1; i++) {
          digitalWrite(i, HIGH);
        }
        break;

      default:
        for (int i = firstLEDpin; i < lastLEDpin + 1; i++) {
          digitalWrite(i, LOW);
        }
        break;


    }//Close switch case.

  }//Close if.

}//Close loop.

Hello Michael,

I am sorry to trouble you but I was hoping you might let me know if the above referenced sketch should be working on my Mega 2600.

My guess is ‘No’, but if you knew for sure I could leave it alone…or buy a new board….(if this proves to be problematic in the lessons to follow).

I know you recommended a simpler board, but I had this one on hand and until today it has worked.

Try as I might I can not get this to work on my Arduino Mega 2560. No LED lights

As I VERY much doubt that there was a mistake in your code, I did the following:

1) verified that other sketches (done to date) still work with my board, they do, so I presume board is not damaged.

2) Tried the following sketch to see the results:

int incomingByte = 0;

void setup() {
  // put your setup code here, to run once:
 Serial.begin(9600); 
}

void loop() {
  // put your main code here, to run repeatedly:
 if (Serial.available() > 0) {
    // read the incoming byte:
    incomingByte = Serial.read();

    // show in serial monitor
    Serial.print("I received: ");
    Serial.println(incomingByte, BIN);
  }
}

And the results were as expected!

3) I then integrated this into your sketch for the lesson. Wow! some strange results.
Still no LEDs were lighting, but the results of Serial.println(incomingByte, BIN);

made no sense whatsoever. Strings of more than 4 letters only returned 4 results (only when putting the above sketch in your lesson sketch ).
4) checked over your code for any sly teaching tricks…(not your style).

So I am guessing (actually hoping) that this is a quirk of arduino MEGA??

Thank you in advance for your trouble,

Gary

Your Challenge:

Take a look at the code…

What do you think, is it an issue with the MEGA or not?  If not, what might be the issue.

Hint:

1. It’s not an issue with the MEGA or the code, but something to do with setting on the Serial Monitor window.

Solution:

Here is what I came up with…

[fvplayer src=”https://vimeo.com/333774013″ transcript=”auto” splash=”https://i.vimeocdn.com/video/779860675_1280x720.jpg?r=pad” caption=”Gary Kahne – MEGA”]