insert-coin

# HW
CHV32V003 or STM32F0 variant

LM386/SC8002B amplifier
* HW PWM filtering for audio



# FW FEATURES
## DEEP SLEEP
* wake from deep sleep on rising edge
* deep sleep when battery voltage is low
* deep sleep on long button press
* deep sleep after some long period of time
    * does not need to be accurate
    * time domain approx. several hours

## BATTERY VOLTAGE MONITORING
* ADC battery voltage reading



## GPIO INPUT
* 4x switch input
    * one for button press
    * one for coin detect

## LED DRIVER
* 3 channels of LEDs
    * need PWM-ish dimming but can be rough (bit-banged) 

## AUDIO
* store audio in MCU flash memory
* 10 audio files with total of 3-5 seconds of audio time
* output using PWM channels, will filter in HW


# REFERENCE
[spec](https://docs.google.com/document/d/1WP9aMegpzNuwF81Cxm263mibuAER9fZ7Ktj7NuHr9Rs)