What This Is

Hold the button briefly for a dot, hold it longer for a dash. Build up a letter, then let the board tell you which letter you sent.

You already know how to time a button press — that was Activity 2.7. The new part is deciding what a duration means, and then looking the answer up.

What You'll Need

• One button, from 3V3 with Pin.PULL_DOWN
• The OLED, or just the terminal if you prefer
• Optional: the speaker, so you hear the dots and dashes as you send them

Build It

1. Time a press. Start the clock when the button goes down, stop it when it comes up. Print the duration in milliseconds.
2. Pick your cutoff. Press the button a lot of times, some short and some long, and look at the numbers. Choose a threshold that separates them for your thumb — nobody else can tell you what it is.
3. Turn a press into a symbol. Below the cutoff is a dot, above it is a dash. Build up a string like ".-" as the presses come in.
4. Decide when a letter is finished. If nothing is pressed for a second or so, the letter is done.
5. Look the letter up. Two lists that line up by position — one of Morse patterns, one of letters — exactly like Activity 1.23.
6. Handle a pattern that is not in your list without crashing.

You do not need all 26 letters. Start with five you can test quickly — E is a single dot, T is a single dash, A is dot-dash, N is dash-dot, and S is three dots.

What Success Looks Like

.  (120 ms)
-  (410 ms)
   letter: A

.  (95 ms)
.  (110 ms)
.  (105 ms)
   letter: S

Then Make It Yours

• Add the rest of the alphabet
• Collect letters into whole words, with a longer pause meaning a space
• Beep the dots and dashes as you send them
• Go the other way: type a letter and have the board flash it at you