SDR toolbox

Nix flake providing programs for exploring an RTL-SDR stick.

Usage

cd ~/projects/sdr
nix develop          # drops you into a shell with all tools
rtl_test             # verify the stick is detected

Or install the whole set into your profile:

nix profile install .#sdr-tools

One-time NixOS setup

The kernel's DVB-T driver grabs the stick, and you need udev rules to use it without root. On NixOS add this to your configuration.nix:

hardware.rtl-sdr.enable = true;   # udev rules + blacklists dvb_usb_rtl28xxu
users.users.bender.extraGroups = [ "plugdev" ];

then rebuild and re-plug the stick.

What's included

Program	Try it for
`rtl_test`	Verify the dongle works
`sdrpp`	Modern spectrum browser — tune around the FM band first
`gqrx`	Classic waterfall receiver
`rtl_433`	Neighborhood 433 MHz sensors: `rtl_433`
`dump1090`	Aircraft tracking: `dump1090 --interactive`
`multimon-ng`	Pagers etc.: `rtl_fm -f 466.230M -s 22050 \| multimon-ng -t raw -a POCSAG1200 -`
`welle-io`	DAB+ digital radio
`satdump`	Weather satellite images (NOAA APT, Meteor LRPT)
`noaa-apt`	Simple NOAA APT decoding
`wmbusmeters`	Decode wM-Bus / OMS smart meters (water, heat, gas, electric)
`rtl_wmbus`	wM-Bus demodulator used under the hood by wmbusmeters
`wmbus-listen`	Convenience wrapper: listen for OMS telegrams (see below)

Listening to OMS / wM-Bus meters

OMS smart meters transmit wireless M-Bus on 868.95 MHz (T1/C1 link modes). wmbus-listen drives the stick via rtl_sdr | rtl_wmbus and hands frames to wmbusmeters.

wmbus-listen                     # discovery: print the id/driver of every meter heard
wmbus-listen Water multical21 12345678 00112233445566778899AABBCCDDEEFF
                                 # decode one meter (needs its id + AES key)

Discovery mode needs no keys — run it, note the ids and drivers that scroll by, then re-run with NAME DRIVER ID KEY to decode a meter you have the key for.

Env overrides: WMBUS_MODES (default c1,t1), WMBUS_FORMAT (json/fields/hr).

Both wmbusmeters and rtl_wmbus are built from source in the flake because they are no longer packaged in nixpkgs.

`oms-tui` — full-screen OMS monitor

A Textual TUI that wraps wmbusmeters: a live list of detected meters on the left, a detail view / live telegram stream on the right.

oms-tui                       # live off the RTL-SDR (868.95 MHz, C1/T1)
oms-tui --replay sample.msg   # offline demo against the bundled capture
oms-tui --import meters.csv    # preload AES keys before listening

Keys:

Key	Action
`Enter`	select the highlighted device (show its details)
`a`	deselect — show the live stream of all telegrams
`k`	set/clear the AES key for the selected device (decrypts live)
`e`	export the current device list to CSV (includes an `aes_key` col)
`i`	import a CSV — loads keys and auto-decrypts those meters
`q`	quit

Details include manufacturer, media/type, driver, version, RSSI, first/last seen, telegram count, the encryption in use (OMS security mode 5 = AES-CBC, mode 7 = AES-CTR, or ELL AES-CTR), TPL/ELL layer info, and — once decoded — the latest measurement values with a timestamp. Unencrypted meters show as open (📖, readable without a key); encrypted ones are locked (🔒) until you add a key, then decrypted (🔓). The device list is in-memory and resets on each start; use e/i to persist.

Both C1 and T1 link modes are listened to by default (--listento=c1,t1); add others (e.g. --listento=c1,t1,s1) if your meters use them.

Workflow: run it, watch meters appear, select one and press k to paste its AES-128 key (32 hex chars) — it decrypts on the next telegram. Press e to save everything (keys included) to CSV, then oms-tui --import that.csv next time to come up already decrypting.

The CSV stores AES keys in plaintext — treat it like a password file.

README.md