Shift and Caps Lock

Two buttons (both to ground): Shift on GPIO5 and a letter key on GPIO6.

• pressing the letter key prints a, or A when it should be upper case
• holding Shift while pressing the letter key flips the case
• tapping Shift on its own (pressed and released with no letter key in between) toggles Caps Lock, printing Caps on or Caps off; Caps Lock flips the case too, so Caps Lock plus Shift gives a

The test, in order: letter at 1.0 s; Shift held 2.0–3.0 s with the letter at 2.4 s; Shift tapped at 3.5 s; letter at 4.2 s; Shift held 4.8–5.8 s with the letter at 5.2 s; Shift tapped at 6.3 s; letter at 7.0 s.