Seventy-three

Radio operators sign off with 73 ("best regards"). Send it in Morse on an LED on GPIO17, forever.

Digits are five elements long: 7 is --... and 3 is ...--. Timing, with a unit of 0.2 s:

• dot = 1 unit on, dash = 3 units on
• 1 unit off between the elements of a digit
• 3 units off between the two digits
• 7 units off after the message, then start again (so the message repeats every 7.2 s)

The first dash starts at 0 s.

Tip: store the code in a dict ({"7": "--...", "3": "...--"}) and write one function that flashes a string of dots and dashes.