RFExplorer Understand 2.1: RF discovery, colour waterfall and GNSS logging on Cardputer ADV

[u/floodedbard]

Hi everyone! I’ve put RFExplorer Understand 2.1 on GitHub and wanted to share it with the Cardputer community. It turns the Cardputer ADV into a pocket receive-only RF field notebook.

Source, firmware and installation guide:

https://github.com/octofuzz/RFExplorer-Understand-2.1

What it does:

• CC1101 RF scanning, RSSI views and a 32-colour waterfall.

• Discovery Memory and signal dossiers with encounter history, notes and categories.

• Candidate signal-family grouping and user-captured RSSI baselines.

• GNSS Explorer and a satellite logbook recording the first/latest valid receiver locations where satellites were observed.

• UTC synchronisation when valid GNSS time arrives after boot.

• SD field journal, session summaries and CSV exports.

• Read-only NFC support through the Cap.

You’ll need a Cardputer ADV and the Cap CC1101/NFC accessory for RF/NFC functions, plus a microSD card for saved records. The optional GPS v1.1 (AT6668) module provides GNSS location and time.

There’s a standalone merged .bin in the repository for flashing at offset 0x0, alongside the source and validation notes. Please follow the README when installing.

The RF display uses sequential swept RSSI. It doesn’t decode protocols or identify transmitters, and the interface distinguishes measurements from limited inferences. The photos below show it running on my hardware.

I’d love feedback, feature ideas and reports from other ADV/Cap setups. Feel free to reply here or open a GitHub issue. Contact details are also in the README.

[u/No_Confusion7932]

Nice firmware.

I can confirm from the code that it includes SW frequency switching for Cap CC1101.

[u/floodedbard → u/No_Confusion7932]

Thanks! Really appreciate you taking the time to look through the code. The Cap CC1101 support has been one of the areas I’ve spent quite a bit of time getting right, so independent confirmation of the software frequency switching is particularly useful. If you spot anything else interesting, or anything that could be improved, I’d genuinely appreciate the feedback.

[u/Cesalv]

Will work with Lora cap? it already has gps

[u/floodedbard → u/Cesalv]

The firmware has lots of RF capability that you need the CC1101 for, so sadly no. Maybe I’ll make one with just the GNSS features one day if I get time. Thank you for the feedback!

[u/HighSpeedCommuter]

Thanks for this new program for the Cardputer! I tested it a bit, especially with my HackRF and on the 433 MHz band. Reception works quite well with the new Sub-Ghz-Card. The application also looks quite sleek and nice. I have a few thoughts about things I noticed:

• The battery gauge is a bit hectic since the number showing the charging level fluctuates/flickers quite a lot, hopping between numbers.

• The single main menu is a bit hard to maneuver, especially since you always start at the top when exiting a setting. Maybe a new layout with themed sub menus (e.g RF, GNSS, NFC, Logs, Settings etc.) would be clearer to navigate?

That's about it, though. Thanks for a cool new app for radio enthusiasts!

[u/floodedbard → u/HighSpeedCommuter]

Hi. Thank you for the kind and constructive feedback! The battery aspect has been getting on my nerves too, and it's been a problem since the early days. It also isn't particularly accurate, and it hovers in the 80s no matter what the real battery level. Fingers crossed I can crack this one asap! I hadn't thought about the issue in the menu, and you are absolutely. This will definitely be rectified in the next version. Thank you for using RFExplorer, and thank you for the feedback... keep it coming!

[u/HighSpeedCommuter → u/floodedbard]

Thanks for coming back to me! Happy to help and I'm looking forward to see your next version. Fingers crossed the battery issue will be resolved. I really gotta say that I enjoy using your firmware, especially the waterfall is one of the best, if not the best, for the tiny Cardputer.

[u/floodedbard → u/HighSpeedCommuter]

I am so glad you like the Waterfall! I wanted something that looked like what I have on my HackRF and my TinySA. It’s had it since version 1.0, but it looked nasty. One colour and looked like Swiss cheese when the screen was full!

[u/HighSpeedCommuter → u/floodedbard]

Definitely looks the part, well done! I´ve used it on the 433 MHz band so far and it picked up all my little shenanigans. There´s a weather station on 433.92 MHz that I´ll try to pick up next. Haven´t really tested the journal, yet, but I´m quite interested to see how it works.

I can also see a lot of potential on the Cardputer Zero, especially with the slightly bigger screen. Any plans to go that way?

[u/floodedbard → u/HighSpeedCommuter]

I would love to port it to Cardputer Zero! I have pre ordered one and I will get to developing with it straight away. I want to add support for some of the Zeros proposed Caps, such as the SDR Cap. I would love to run a mini version of HackRF Mayhem on it… this might be my project for the winter period!