A minimal low-power programmable LED light originally designed to be embedded within plastic toys.
A TPS61040 boost converter is used to provide a constant current for 2-8 white LEDs in series. An ATtiny10 is used to provide PWM control to the boost converter. A momentary switch us used for power and mode control. The schematic includes pull-up resistors for the button and reset line, however internal pull-ups appear to be sufficient. If low forward-voltage diodes are used the light can be operated below 1V per cell.
The firmware has 4 modes - off, low brightness, full brightness and flashing. Other modes can be added by modifying the main switch statement.
The build.sh script can be used to build and flash the firmware. The script requires avr-gcc, avr-objcopy and avrdude to be installed. By default it expects a USBASP programmer.