Development of Time-division Multiplexing Scanner for Weather Stations of Different Protocols Using Software Defined Radio

A weather-monitoring system has been developed such that it receives data from multiple weather stations and sends said data into an online database. It employs two software-defined radios (SDRs) acting as receivers, one that is dedicated for a specific weather station, while the other switches between two other weather stations that have different frequencies and protocols.

Software Functionality

Most of the system runs on python code. The particular functionality are the following:

1. Switching between rtl-433 (General sensors) and SDRangel (LoRa-based stations)
2. Rtldavis activation
3. Storage of data from Davis stations
4. Uploading of data to the CARE database

Software Dependencies

This system requires certain software/dependencies as detailed below. These software (aside from Arduino IDE) are mainly for Linux-based operating systems.

SDR drivers

In order for the Raspberry Pi to communicate with the SDRs, their respective drivers must be installed first. For RTL-SDR, installation procedure for Linux systems can be found here, while for the ADALM-Pluto, its procedure can be found here or simply access the info.html file when the Pluto is plugged in (the latter is more reliable).

NOTES

RTL-SDR

• Successful driver installation can be tested using the rtl_test command.
• If using Raspberry Pi 4, invoking multiple (at least 2) rtl_test may cause an error. Solution to this is either:
  • use a Raspberry Pi 3, since the error does not occur for that model
  • unplug and replug the RTL-SDR device

ADALM-Pluto

• the libiio package must also be installed
• successful installation can be verified via iio_info -s

Rtldavis

This is the software used for decoding Davis Vantage Vue stations. Installation process is detailed by user guidocini in their guide. However, for the purposes of this study, only steps 2-4 in the guide are important.

Rtl_433

This software is used to decode data from WH31E and WH40, or the general sensors. The installation guide can be found in the rtl-433 github page by user merbanan. SoapySDR and/or RTL-SDR must first be installed in order for the SDRs to use it.

SDRangel

This software is used for decoding LoRa signals. The installation process can be found in the wiki page of the SDRangel github page made by user f4exb.

NOTES

• Not all hardware dependencies are required, select only the ones that are needed (for this study, only ADALM-Pluto is needed for SDRangel) and reflect the changes in the final build command, accordingly.
• SDRangel requires the powerdown attribute of Pluto to be 0 in order for it to be used as a receiver. This can be done by using the iio_attr -u ip:192.168.2.1 -c ad9361-phy altvoltage0 powerdown 0 command.

Arduino IDE (not installed in Raspberry Pi)

This is used for coding the LoRa transmitters. It can be installed by following this guide.

Usage

Assuming all software has been installed, the four python files should be downloaded. These should all be contained in a single directory. Then, specify the desired output file for each station in the main_program.py file. Afterwards, simply run the file via command terminal using python main_program.py or python3 main_program.py.

Recommendations

• Centralize all stations into one radio via implementing a version of rtldavis that is compatible with ADALM-Pluto, i.e., create a custom program.