This repository contains the firmware for a radiation monitor / weather station based on my IoT Geiger Counter board and a Moteino R6.
The measurement data will be transmitted via LoRaWAN which can be used everywhere where no WiFi is available and a high range (1 km) to the base station (gateway) is required. Due to the relatively low power consumption of about 15mA, solar / battery operation is also possible.
A JavaScript payload decoder tested with TheThingsNetwork v3 and ChirpStack v4 is provided.
Besides of the IoT Geiger Counter board, the following components are needed:
- Moteino R6 (16MHz or 8MHz variant, latter requires the 3.3V LDO to be installed)
- RFM95W LoRa Module
- MB85RS64T SPI FRAM (strongly recommended for LoRaWAN session data storage)
- BME280 temperature, humidity, barometric pressure sensor (optional)
- u.fl jack & 868 MHz LoRa antenna
- USB serial adapter with 5V VCC and 3.3V logic level for programming (Moteino FTDI Adapter, Adafruit FTDI Friend or my Serial Adapter)
- Atmel AVR ISP for bootloader burning (optional, 3.3V, USBASP or similar)
The processor on the Moteino R6 is an Arduino compatible Atmel ATMega328P. The project therefore utilizes the popular MCCI Arduino LMIC library for LoRa. For easy compilation and deployment, the PlatformIO toolchain is used.
The LoRaWAN implementation supports OTAA and ABP. Session data (e.g. session keys, frame counter) will be stored in the SPI FRAM chip from time to time. That is done immediately after joining the network and also after each third data packet has been sent. The advantage of FRAM over flash memory is a much higher number of write cycles, but it is still a good idea to limit them a little bit.
To count the pulses of the GM tube, D5 (Timer 1) is used. Since Timer 0 is occupied by the Arduino libraries, Timer 2 serves as clock source for the gate time. By counting the overflows, a 60s interval can be generated to read and reset the current counter value.
Due to restrictions of the 868MHz ISM band, the transmission time per hour is limited. To meet these Duty Cycle requirements, data is collected over a five-minute interval and an average CPM value is calculated and sent.
If a BME280 sensor is connected, temperature, humidity and barometric pressure data is also included in the transmission.
Three additional wires are needed to connect the pins DIO0 (Tx/RxDone), DIO1 (RxTimeout) and DIO2 (TimeoutFSK) to the GPIOs D2, D3 and D4 as shown in the picture below.
Please follow the guides on platformio.org to either install PlatformIO core (for console operation) or VS Code & PlatformIO (IDE). Then clone this repository and change to the correct directory.
As the DualOptiboot bootloader did not work in my setup, I suggest flashing the default Arduino bootloader. To do that simply connect MISO, MOSI, SCK, +3.3V and GND of your USBASP to the Moteino. Please make sure the programmer is set to 3.3V voltage, as the RFM95W is not 5V tolerant! If the RFM95W and FRAM chip are already soldered in, you might need pull-up resistors on the NSS and /CS lines (D10, D8) as well. After that, just execute "pio run -t bootloader -e isp16mhz" (or isp8mhz) to program bootloader and fusebits.
Copy the file src/config.h.example to src/config.h. Then uncomment either USE_OTAA or USE_ABP, create a new device on your LoRaWAN server and fill in the initial session data in config.h as described therein. You can find the required payload decoder in docs/payload-decoder.js.
When everything is configured, simply plug the USB serial adapter into your Moteino. Then execute "pio run -t upload -e moteino16mhz" (or moteino8mhz) to program the firmware.
You might check the serial console for log messages of your IoT Geiger Counter by using the command "pio device monitor". The network will be joined immediately after power up. Measurement values will be transmitted every five minutes.
Once the LoRaWAN activation is completed, the session data is stored in FRAM and recovered at boot. A hash value of config.h is included to detect configuration changes and invalidate the current session, forcing the device to re-activate.
The LED on the moteino will light up if a packet is being sent. It will blink if the OTAA activation fails.
https://www.maltepoeggel.de/?site=iotgeiger
https://lowpowerlab.com/guide/diy-moteino/
https://github.com/LowPowerLab/Moteino
This firmware is released under the terms of the MIT license, see LICENSE file for details.