Using the Telemetry and APRS Applications

Faraday owners will find that the Telemetry and APRS applications are fun to play with. We encourage you to play with them shortly after going through the Quickstart guide!

Telemetry

Out of the box, a GPS enabled Faraday is quite capable. The GPS provides location awareness for Faraday without extra hardware. It is also a tool that future software will leverage more. ADC data is also transmitted down as raw bits. Soon this will change to volts at the ADC pin. However, we can post-process this data to get engineering units prior to this update.

DB Browser for SQLite immediately provides access to the telemetry database telemetry.db. Rows corresponding to every telemetry transmission received by Faraday are available for viewing, editing, and exporting. Having the ability to plot data while new telemetry packets are streaming in is useful when debugging. Callsigns and other data can also be manipulated to aid in development efforts.
dbbrowser for sqlite

In a recent long-duration test, Faraday transmitted overnight. Here in Los Angeles the temperature hovered at 10 Celsius at night. RF telemetry data was being sent out every ten seconds for 9 hours and 40 minutes. Faraday was brought inside for the night about one hour into the test. The PCB warmed up to 20C until sunrise when the board warmed up with the Sun. These events are clearly shown in the graph below.

Faraday Board Temperature and External VCC graph

What is also clear is the 9V Li-Ion battery discharging overnight. The voltage bumped up when the battery warmed as the setup came inside. The ADC data was converted from bits into volts with Excel to show battery voltage. We will write additional blog posts about using the ADC pins for remote data sensing.

The Antennova GPS speed is a clear indicator of GPS performance. When outside for the first hour of operation the speed hovered near zero once a GPSfix of 2 was achieved (DGPS). Once taken inside the house, even near a window, the speed became sporadic. This manifested as a wandering altitude and lat/lon position. In-fact, the GPS was so accurate that the APRS system indicated no movement until it was inside the house.

GPS Speed long duration test

APRS

Faraday bridges the ham radio and web-development worlds. Applications that use a network interface to communicate make porting data around the internet easy. The APRS application does this to make Faraday join the APRS-IS network. This is a one-way link now but in the future it will expand.

Faraday bridges the ham radio and web-development worlds

This application queries the telemetry database once per minute. First it checks what stations have updated their telemetry in the previous five minutes using the telemetry “/stations” API. Then the database is queried for each one of these stations to return the latest telemetry transmission. The application then generates APRS compliant position, telemetry, label, and equation strings. Every string is then sent to the APRS-IS server while connected with a user-dependent login thanks to code from Magicbug ported to Python.

Telemetry application stations
Once sent to APRS-IS, websites such as aprs.fi display the data with online maps. There are even many Android and iOS applications which provide this service. Faraday appears like any other APRS station. Except it is not on 2 meters and is actually on 33cm transmitting much quicker than once per minute! The Telemetry application saves the high-resolution data while APRS saves course data.

Faraday Rev D1 Venice CA
I walked around Venice, CA today with Faraday running a quick test. The base station was a Faraday radio inside my house sitting on a table, non-optimal. APRS packets were sent to the APRS-IS system once per minute resulting in the map plot below.

APRS Map Venice California CA
Raw packets generated by the Faraday APRS application are saved for several days on aprs.fi. As you can see KB1LQC-1 receiving telemetry from KB1LQC-2.

APRS.fi raw packets
The station info page on aprs.fi shows detailed path data as well as some historical items too. The APRS application usually get flagged for having a high update rate. However, the position packets indicate no RF digipeating transmissions should occur. Therefore, 60 second transmission intervals seems more than reasonable. It is 2017, updating telemetry and position data more than once per minute should be standard.

APRS.fi station information aprs
Faraday radio owners can help setup a pseudo network by providing base stations to gather Faraday telemetry. As you and others in your area start using Faraday radios it will port the data into APRS-IS for all to see. A taste of what networked Faraday radios can do. We don’t believe the future network Faraday will be car tracking oriented but we do believe that distributed access points are the way forward. Tracking radio positions will just be a portion of the capabilities.

Open Source Development

If you’re not subscribed the FaradayRF Newsletter you are missing out on the latest progress. Those interested in lending a hand should watch our Github Software Repository. Since sending out hardware, the APRS and Telemetry applications have matured quickly! These applications represent the most basic of use-cases Faraday can fill. They are open source and just an example of what is to come.

 

Bryce Salmi, @KB1LQC

@FaradayRF

Author: Bryce Salmi

Licensed radio amateur KB1LQC and Co-Founder of FaradayRF. Professional Electrical Engineer designing and building avionics for rockets and spacecraft during the day and developing the future of digital amateur radio experimentation by night. All opinions are my own.

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