Packet.Ax25.Radio 0.36.0

Packet.Ax25.Radio

What a radio's control channel is worth to an AX.25 link: per-frame signal metadata, and real RF carrier-sense feeding the CSMA gate.

M0LTE.Rig models the control channel to a radio (RSSI, hardware DCD, PTT) without knowing anything about packet. This package is the adapter layer that brings it into the AX.25 stack.

Install

dotnet add package Packet.Ax25.Radio

Types

• RssiTaggingTransport - an IAx25Transport decorator. A background sampler polls RSSI (fast while the channel is busy, slow while idle so the idle samples track the noise floor) and re-yields every inbound frame with Ax25InboundFrame.Radio populated: RSSI median/min/max/sample-count, SNR, noise floor, carrier-rise instant, burst index (an AX.25 frame train shares one carrier), airtime estimate, and, for the first frame of a burst, the measured pre-data carrier time, which is the sender's effective TXDELAY and an excess-TXDELAY detector input. A frame with no qualifying sample gets null metadata, never a guess.
• RadioCarrierSense - CSMA by hardware DCD, done natively by the stack. It bridges the radio's ChannelBusy onto the neutral ICarrierSense seam that Ax25Listener consults before every keyup, via Ax25ListenerOptions.CarrierSense. The listener's own CarrierSenseGate holds the keyup while the channel is busy (bounded wait, fail-open), so the medium-access deferral lives in the stack rather than an opaque transport wrapper, and composes with the TNC's own persistence CSMA.

Hardware DCD typically calls the channel busy 0.5-1 s before the modem finishes demodulating the frame, which is exactly the head start a CSMA gate wants.

Usage

using M0LTE.Tait.Ccdi;
using Packet.Ax25.Radio;

await using var radio = TaitCcdiRadio.Open("/dev/ttyUSB0");
await radio.SetProgressMessagesAsync(true);                   // turn on DCD events

await using var tnc = NinoTncSerialPort.Open("/dev/ttyACM1"); // from Packet.Kiss.NinoTnc
await using var tagged = new RssiTaggingTransport(tnc, radio);

var listener = new Ax25Listener(tagged, new Ax25ListenerOptions
{
    CarrierSense = new RadioCarrierSense(radio),
});

await foreach (var frame in tagged.ReceiveAsync(ct))
{
    // frame.Radio?.RssiDbm / frame.Radio?.SnrDb now populated
}

With carrier-sense, frames are attributed to the transmission window containing their arrival. Without it, RssiTaggingTransport falls back to a threshold-over-noise-floor filter and the window-derived fields (carrier-rise, burst index, pre-data carrier) stay null. NoiseFloorDbm exposes the live idle-sample estimate.

Both types leave ownership of the inner transport and the radio with the caller; disposing the decorator only stops its sampler.

See also

• M0LTE.Rig - the radio-control contract this adapts
• Packet.Ax25.Radio.Tait - AX.25 over a Tait's own FFSK modem, no TNC at all
• Source & issues

AGPL-3.0-licensed. Part of the Packet.NET stack.