Imported from GitHub: hierle/letterbox-sensor-v2 · commit b3c91ce · license GPL-3.0

Description

LoRa / LoRaWan letterbox sensor v2

README

LoRaWan EU868MHz Letterbox Sensor v2

sensing letters in your letterbox via two infrared proximity sensors (HSDL9100), sending out status via lora / lorawan, using RAK3172 (based on STM32WLE5CC) CPU/RF, powered by a CR2032 battery.

This project was inspired by the heise ct briefkasten sensor project https://www.heise.de/ratgeber/IoT-Netz-LoRaWAN-Briefkastensensor-mit-hoher-Reichweite-selber-bauen-4417179.html https://github.com/jamct/radio-mailbox and is a direct successor of version 1: https://github.com/hierle/letterbox-sensor

Contents:

• ./PCB/ : kicad PCB files
• ./letterbox-sensor-v2/ : lorawan letterbox sensor sketch
• ./misc/ : payload decoder, sample http integration cgi

An extended web ui by Peter is available here: https://github.com/pbiering/letterbox-sensor-web

A nice alternative software by Henrik, using Lora P2P mode is available here: https://github.com/HonkStonk/MightyMailbox

Compiled and flashed with ArduinoIDE with RAKWireless STM32 extensions

Features:

• using RAKWireless RAK3172 based on STM32WLE5CC
• deep sleep at (measured) 5uA including battery voltage divider and tantalium caps
• two proximity sensors HSDL9100
• USB-C interface for flashing and serial monitor, via FT230XS-R USB-UART
• onboard 868MHz PCB antenna after TI document http://www.ti.com/lit/an/swra227e/swra227e.pdf
• lorawan activation either ABP or OTAA
• battery voltage measurment thru voltage divider (2x 10MOhm)

Changes to v1:

• replaced ATTiny and RFM95 with RAK3172, much more CPU power and memory, much simpler code
• support for OTAA lorawan activation
• much simpler software stack, using ArduinoIDE with RAKWireless STM32 extensions and API usage
• added USB-C interface, no more special programming interface needed
• added second HSDL9100 for better physical letterbox coverage
• added two (optional) supporting tantalium caps for extended battery life
• removed temperature, as not easily avail on STM32WLE5CC / RAK API
• removed trimmers

BOM (digikey.de):

Count	Part number	Description	Usage
1	RAK3172-8-SM-NI	CPU/RF-Lora NO IPEX!	CPU/RF module
2	CS1213AGF260	Tactile switch	Boot/Reset
2	HSDL-9100-021/024	Proximity Sensor	Proximity sensors
2	CRGCQ1206F33R	RES 33 Ohm 1206	Proximity sens LED
2	CRGCQ1206F1M0	RES 1M Ohm 1206	Proximity sens diode
1	BU2032SM-FH-GTR	CR2032 COIN CELL HOLDER	Battery
2	TAJE477M010RNJ	CAP tant 470u	Battery supporting caps
1	LQG18HN1N8S00D	IND 1.8NH 0603	Antenna matching
1	GRM1885C1H2R7CA01D	CAP 2.7PF 0603	Antenna matching
3	GRM188R72A104KA35D	CAP CER 0.1u 0603	Suppressor caps
2	GRM188D71A106KA73D	CAP CER 10u 0603	Suppressor caps
1	RAHUC31AUTR	USB-C connector	USB
1	FT230XS-R	FTDI USB Serial UART	USB UART
1	MI0805K601R-10	Ferrite bead 0805	USB power
2	AC1206FR-075K1L	RES 5.1k Ohm 1206	USB power sens
2	CRGCQ1206F22R	RES 22 Ohm 1206	USB lines
1	GRM188R72A104KA35D	DIP switch	Power switch USB/Battery
2	AA3528LSECKT/J4	LED orange	Status/USB status
2	CRGCQ1206F220R	RES 220 Ohm 1206	Status LEDs
2	RC1206FR-0710ML	RES 10M Ohm 1206	Battery voltage measure

RAK3172 documentation:

https://docs.rakwireless.com/Product-Categories/WisDuo/RAK3172-Module/Overview/

How to compile:

Follow the instructions on https://docs.rakwireless.com/Product-Categories/WisDuo/RAK3172-Module/Quickstart/ in short:

• install ArduinoIDE from arduino.cc
• add the following URL to the boards manager URLs section in preferences: https://raw.githubusercontent.com/RAKWireless/RAKwireless-Arduino-BSP-Index/main/package_rakwireless.com_rui_index.json
• install the "RAKwireless RUI STM32 Boards" from the Boards Manager
• select "WisDuo RAK3172 Evaluation Board" board
• on Mac you might need to install pyserial: sudo pip3 install pyserial
• on Linux you might need to install python3-pyserial
• connect the board, make sure it's powered on (DIP switch)
• select the corresponding serial port
• open the sketch folder
• adjust config.h and lorawan.h
• compile and flash

For configuration adjust config.h and lorawan.h

config.h:

• PERIOD: the time intervall you want the sensor to send it's data, in minutes, default is 30 minutes
• THRESHOLD: the threshold for the sensor readings (empty/full), can later be "overwritten" in e.g. HTML integration
• USE_OTAA: if true, OTAA will be used instead of ABP, so we do not have to worry about frame counters after reset / battery change
• DATARATE and TXPOWER: adjust to your needs, your packets should be reliably received, w/o wasting to much power
• see also the comments for each entry in config.h

lorawan.h:

• set your lorawan keys for either ABP or OTAA
• OTAA_APPEUI or JOINEUI is only needed to select a specific JOIN server, in private networks can be set to any value

Additional notes:

• you will need a DATA USB-C cable, a charging only cable will not work, as it's missing the data pins ;-)
• the DIP switch allows to power the device directly from USB, but when using the battery in production environment (letterbox), it should be switched off, not to waist power on the FT230 USB-UART chip

Letterbox sensor v2 lorawan payload package byte structure:

byte	0	1 2	3 4	5 6	7
	0x00=empty	battery	sensor1	sensor2	threshold
	0xFF=full	voltage	raw	raw

Todos:

• read battery voltage and temperature from STM32
• see sections 3.18.1 and 3.18.3 in: https://www.st.com/resource/en/datasheet/stm32wle5c8.pdf

Have fun!