To-do

My notepad for remaining tasks.

• Raspberry Pi - the main controller of the system
• Create a HAT add-on board (Hardware Attached on Top)
• Design in KiCAD
• 40-pin connector
• IO <= Memo to me: I am here!
• 74HC244 octal buffer/line driver
• MOSFETs
• MAX3483  RS-485 transceiver (link to microcontroller)
• ID EEPROM (HAT requirement)
• https://github.com/raspberrypi/hats/blob/master/eeprom-circuit.png
• Memory Chip 24C32 serial EEPROM 2.7-5.5V 32K SOP-8
• Back power protection (HAT requirement)
• https://github.com/raspberrypi/hats/blob/master/designguide.md
• https://github.com/raspberrypi/hats/blob/master/zvd-circuit.png
• Polyfuse
• Power supply
• 12V => 5V conversion with a LM2576 or LM2596.
• Must supply at least 1.3A, preferably 2A to the RPi.
• 3.3V is taken either from the RPi  or from a simple linear regulator.
• Power monitor
• PAC1720 Dual High-Side Current Sense Monitor with Power Calculation
• Precision 0.22 ohm resistors
• Input 1: The connection between the battery charger and the 12V sealed lead acid battery. Here we can measure the current charging the battery - and detect mains power failure I suppose.
• Input 2: The connection from the 12V battery to rest of the system (power supply, solenoid lock etc). Here we can measure consumption. 
• Etch the PCB
• Mount and solder components
• Test the board
• Program HAT EEPROM
• Software
• Design
• Select components
• Python implementation of Nick Gammon's RS485 library for the Arduino.
• Test against program running on the microcontroller
• Enclosure for
• 12V sealed lead acid battery
• Battery charger (230VAC => 12VDC)
• Raspberry Pi with HAT
• Arduino-like microcontroller - untrusted I/O controller
• PCB
• Design in KiCAD
• Power
• 5V and/or 12V is available from the main controller
• Find power requirement: XXX mA @ 3.3V
• 3.3V is taken from a simple linear regulator
• Core
• Atmel ATmega328P
• Crystal
• ICSP pins til In-System Programming
• SPI (SCK, MISO, MOSI)
• ~RESET
• VCC
• GND
• IO
• Keypad, PCF8574T Remote 8-bit I/O expander
• I²C
• Display
• SPI
• ISO 14443 MFRC522 board
• SPI
• EM4100 125kHz reader
• Serial
• DS18B20 thermometer
• 1 I/O
• Buzzer
• 1 output
• MAX3483 RS-485 transceiver (link to RPi)
• Serial
• Etch the PCB
• Mount and solder components
• Test the board
• Software
• ...
• Mounting and cabling
• Somewhere hidden
• The enclosure with the Raspberry Pi main controller
• In doorframe
• Reed contact to detect if the door is really closed.
• Microswitch in the back of the strike plate to detect if the dead bolt is in place.
• Lead cover (protection for the cable from the door to the frame)
• Cabling from contacts and lead cover to main controller
• In door
• Ruko/Abloy EL582 solenoid lock.
• Recessed magnet for the reed contact in the doorframe.
• Cabling from lock to lead cover 
• In/behind fiber cement siding next to door (outside)
• Keypad
• Cut hole in fiber cement with angle grinder
• Mount with aluminum backplate and 4 nuts.
• Display
• Cut hole in fiber cement - drill, cut?
• Cut and mount acrylic glass or glass for waterproofing. 
• Nokia 5110 84x48 pixel display behind the glass.
• Card readers behind the siding
• For ISO 14443A cards (like MIFARE and NFC)
• For EM4100 125kHz RFID cards.
• Engrave or laser cut guides on front so we can see where to scan the cards.
• DS18B20 thermometer
• Buzzer
• In wall next to door (inside - or perhaps nearer the I/O components)
• Arduino-like microcontroller - untrusted I/O controller
• Connections to keypad, display, card readers.
• Cabling to the main controller