Code and electrical schematic for a garage parking proximity meter.

Hardware:

• MCU - Atmel AVR attiny2313
• Ultrasonic distance sensor - MaxBotix LV-MaxSonar-EZ
• Adafruit LIPO/Li-Ion battery charging circut

source

• 3rd-party/ - 3rd-party dependancies

• utils/ - break out reusable code for bit operations and led manipulation, with unit tests

• sonar-pwm-3led/ - receive sonar signal via a pulse width signal, change LED color depending on distance.

• sonar-usart-3led-sleep/ - receive sonar signal over serial signal, change LED color depending on distance, sleep mcu when readings are stable, periodically wake to detect changes.

External dependencies

Build and flash requires avr-gcc, avr-libc and avrdude

Building on macOS with homebrew requires:

• avrdude
• osx-cross/avr/avr-gcc
• osx-cross/avr/avr-libc
• osx-cross/avr/avr-binutils

cmocka is used for C unit testing. Source is included in this repo, and can be built with:

cd 3rd-party
make cmocka

Circuit schematic requires KiCad

TODO

• disable sonar ranging and periodically wake up to preserve battery.