Ledplay

Ledplay is a small project aimed as a childrens toy. It uses a Cortex M0+ (Kinetis KE04, MKE04Z8VWJ4) to light button leds in binary order, waiting for them to be pressed. When a complete number has been pressed, it progresses to the next, until all have been exhausted. It then resets from one.

Copyright (C) 2016 Andreas Bofjäll andreas@gazonk.org, see LICENSE for licensing details.

DESIGN RATIONALE

Power efficiency was paramount, but I still wanted to retain programmability and flexibility for future use cases. The whole circuit is running at around 130 uA when no leds are lit, giving it a runtime of about 1 to 1.5 years on two double AA batteries. There are no current limiting resistors for the leds and the led dc-dc drives them using constant voltage, but they won't be lit long enough for their resistance drop to become a problem.

The led dc-dc is a SEPIC because originally, the leds would be driven with a lower voltage, but they turned out to be too dim.

SCHEMATICS AND PCB

Schematic and PCB are made in Kicad. The PCB is a four layer board (mostly because I wanted to play with multilayer boards).

COMPILING

Enter the src directory and run "make". You need a standard gcc arm toolchain (arm-none-eabi-*) installed, but nothing else. Ledplay does not use CMSIS.