“Serial (ascii) monitor with 9 lines of 28 char.
Baudrate from 2400 up to 256000 baud.
Digital 3.3V or 5V input.
Powered by a single Lithium-Ion battery. (3.7V nominal)
Supplies:
ILI9341 display (here a parallel version is used)
BluePill (or other board with a STM32F103C8)
74HC14 (hex invering schmitt trigger)
3.3V low dropout voltage regulator
rotary encoder (with or without button)
lithium ion battery (e.g. from old telephone)
some capacitors and resistors
power switch
project box
PCB (perfboard)”