Arduino Code - Code will not compile

Question

I am building a type of telegraph with my Arduino and instead of using Morse code I am taking each character and giving it a value of 1-26 (a-z), 27 for a space and 28 for unknown. Then I convert that number to binary. But I keep getting errors. Could someone please help me? Thanks!

int button_0 = 13;
int button_1 = 12;
int out_0 = 11;
int out_1 = 10;
int in_0 = 9;
int in_1 = 8;
int buzzer = 7;
void setup() {
 pinMode(button_0, INPUT);
 pinMode(button_1, INPUT);
 pinMode(out_0, OUTPUT);
 pinMode(out_1, OUTPUT);
 pinMode(in_0, OUTPUT);
 pinMode(in_1, OUTPUT);
 pinMode(buzzer, OUTPUT);
 Serial.begin(9600);
}
void loop() {
 Serial.println("Message to binary: ");
 String input = "Hello World";
 String message = input.toLowerCase();
 String binaryNumber = "";
 for(int i = 0; i <= message.length(); i++) {
 char l = message.charAt(i);
 int letter = 0;
 if (l == 'a') {
 letter = 1;
 } 
 else if (l == 'b') {
 letter = 2;
 } 
 else if (l == 'c') {
 letter = 3;
 } 
 else if (l == 'd') {
 letter = 4;
 } 
 else if (l == 'e') {
 letter = 5;
 } 
 else if (l == 'f') {
 letter = 6;
 } 
 else if (l == 'g') {
 letter = 7;
 } 
 else if (l == 'h') {
 letter = 8;
 } 
 else if (l == 'i') {
 letter = 9;
 } 
 else if (l == 'j') {
 letter = 10;
 } 
 else if (l == 'k') {
 letter = 11;
 } 
 else if (l == 'l') {
 letter = 12;
 } 
 else if (l == 'o') {
 letter = 13;
 } 
 else if (l == 'm') {
 letter = 14;
 } 
 else if (l == 'n') {
 letter = 15;
 } 
 else if (l == 'p') {
 letter = 16;
 } 
 else if (l == 'q') {
 letter = 17;
 } 
 else if (l == 'r') {
 letter = 18;
 } 
 else if (l == 's') {
 letter = 19;
 } 
 else if (l == 't') {
 letter = 20;
 } 
 else if (l == 'u') {
 letter = 21;
 } 
 else if (l == 'v') {
 letter = 22;
 } 
 else if (l == 'w') {
 letter = 23;
 }
 else if (l == 'x') {
 letter = 24;
 } 
 else if (l == 'y') {
 letter = 25;
 } 
 else if (l == 'z') {
 letter = 26;
 } 
 else if (l == ' ') {
 letter = 27;
 } 
 else {
 letter = 28;
 }
 binaryNumber = binaryNumber + String(letter, BIN) + " ";
 }
 Serial.println("Message to binary:\n"+binaryNumber);
}

Here is my error:

binary_telegraph.cpp: In function ‘void loop()’:
binary_telegraph.cpp:37:38: error: conversion from ‘void’ to non-scalar type ‘String’ requested

• angelatlarge: What kind of errors are you getting?

Answer 1

toLowerCase() function converts the object being called on to lower case. It doesn't return anything. So what you probably want to do is:

String input = "Hello World";
String message = input;
message.toLowerCase();

This explains the error: you put a void, a nothing, in the variable message. This is not an unreasonable error to make, according to the documentation:

Get a lower-case version of a String. As of 1.0, toLowerCase() modifies the string in place rather than returning a new one.

So the toLowerCase() function used to return a lower-cased version of the string. Now it just modifies the string being called on, and not return anything.

Now, at line 37:

for(int i = 0; i <= message.length(); i++) {

You expect message to be a String, as you call the length method. Now, the compiler attempts to convert the void in message to a String, but that's not possible. Therefore, you get an error.

P.S. As a general rule, here's my personal process for debugging these sorts of errors:

• Look at the line where the error occurs
• Check the documentation for all the functions used on that line (in this case here)
• If that doesn't solve it, double-check my assumptions about the language syntax based on the error message.