DigiPi Hotspot — Vol 4: Reference

4.1 About this volume

This is the scannable reference: the tables, the default access details, a mode-to-interface matrix, a glossary, sources, and a consolidated list of every “verify on a real unit” item flagged across Volumes 1–3. It repeats key facts deliberately so you can work from this page alone with a card and a radio in front of you.

4.2 Modes at a glance

Table 1 — Modes at a glance

Mode	App / engine	Typical band & use
APRS (beacon, WebChat, digipeater, IGate, map)	Direwolf	VHF FM (144.390 MHz NA); position/messaging/infrastructure
AX.25 packet	Direwolf (KISS TNC)	VHF/UHF FM; BBS, keyboard-to-keyboard, networking
Bluetooth rfcomm TNC	Direwolf + BT pairing	VHF/UHF; wireless TNC for a phone app (e.g. APRSdroid)
Winlink (HF)	Pat + ARDOP	HF SSB; long-haul radio email
Winlink (VHF)	Pat + packet (Direwolf)	VHF/UHF FM; local radio email via RMS gateway
FT8	WSJT-X	HF SSB; weak-signal structured contacts
JS8Call	JS8Call	HF SSB; weak-signal keyboard-to-keyboard messaging
CW / PSK31 / RTTY / MFSK	FLDigi	HF (mostly) SSB; classic keyboard modes
SSTV	FLDigi (verify)	HF/VHF SSB; slow-scan still images
Rig control (CAT)	rigctld (Hamlib)	USB rigs; frequency/mode/PTT over USB

4.3 Interface-board comparison

Table 2 — Interface-board comparison

Interface	Rough price	Fits which radios	Notes
(none — USB cable)	cable only	USB-CAT rigs: IC-7300, IC-705, FT-991, Xiegu	Audio + CAT + PTT over one USB cable; no board
Masters Comm. DRA-Pi-Zero	~$75	Non-USB rigs (HTs, FM mobiles)	Purpose-built for DigiPi; mounts on Pi Zero header; cleanest build
DigiPi Hat	~$40	Non-USB rigs	Purpose-built hat, lower cost
Fe-Pi Audio Z v2 + N7EBB RIB	~$24–34 + ~$25	Non-USB rigs	Sound card + ready-made PTT interface box
Fe-Pi Audio Z v2 + DIY PTT	~$24–34 + few $	Non-USB rigs	Sound card + 2N7000 MOSFET & 100 kΩ resistor keyed by Pi GPIO
Digirig Mobile + cable	(verify)	Non-USB rigs (with matched cable)	USB interface puck; sound + CAT/PTT; not a hat
AIOC “All-In-One-Cable”	~$25	Baofeng/Kenwood (K1) HTs	USB sound + serial PTT in one inline cable

All prices are approximate and drift — confirm against craiger.org and the vendors (see the checklist at the end).

4.4 Default access

The first-run “hotspot” flow, in order:

1. Join DigiPi’s access point. On first boot DigiPi is its own Wi-Fi AP:
   • SSID: DigiPi
   • Default password: abcdefghij (vendor’s published default)
2. Hand it your home Wi-Fi. With your phone/laptop joined to DigiPi, browse to:
   • http://10.0.0.5/wifi.php
   • Enter your home Wi-Fi SSID and password there.
3. Reach it on your home network. After it joins your Wi-Fi, DigiPi is available at:
   • http://digipi/
4. Initialize the station. Open the Initialize page to set your callsign, grid square, and localization.

No monitor or keyboard is needed at any point — the whole flow is headless, in a browser. An optional small GPIO display can show status but is not required.

TBD — verify. Confirm the AP SSID/password, the 10.0.0.5/wifi.php URL, the http://digipi/ hostname, and the exact fields on the Initialize page against a real unit / craiger.org. Defaults can change between image versions.

4.5 Mode → interface-requirement matrix

Which signals each mode needs from your interface. “CAT” = frequency/mode control; “Audio” = TX and RX audio; “PTT” = keying line.

Table 3 — Mode → interface-requirement matrix

Mode	Audio (RX+TX)	PTT	CAT	Notes
APRS / packet (VHF FM)	Yes	Yes	No	GPIO/RIB PTT on a non-USB HT/mobile; no CAT needed
Bluetooth TNC	Yes	Yes	No	Same as packet; TNC exposed over Bluetooth to a phone
Winlink VHF (packet)	Yes	Yes	No	FM rig + interface board
Winlink HF (ARDOP)	Yes	Yes	Recommended	HF SSB rig; USB-CAT rig carries all four over one cable
FT8 (WSJT-X)	Yes	Yes	Recommended	Time-critical; USB-CAT rig ideal
JS8Call	Yes	Yes	Recommended	Shares plumbing with WSJT-X
FLDigi (CW/PSK31/RTTY/MFSK/SSTV)	Yes	Yes	Optional	Manual tuning workable; CAT convenient

On a USB-CAT rig all of Audio + PTT + CAT arrive on the single USB cable. On a non-USB rig, Audio comes from the sound-card interface and PTT from a GPIO/serial line (there is no CAT unless you add a separate CAT cable).

4.6 Quick-start recap

The end-to-end path from bare parts to on-the-air, condensed:

1. Choose a radio — an FM HT/mobile for APRS/packet/VHF-Winlink, or an HF SSB rig for FT8/JS8Call/ARDOP-Winlink. A USB-CAT rig (IC-7300, IC-705, FT-991, Xiegu) is the simplest.
2. Choose an interface — nothing but a USB cable for a USB-CAT rig; otherwise a Type-B board (DRA-Pi-Zero, DigiPi Hat, Fe-Pi + PTT, Digirig, or AIOC).
3. Get and flash the image — download the Patreon-gated SD image (from $1), unzip, and write to a ~8 GB+ microSD with Raspberry Pi Imager or balenaEtcher.
4. Boot and join — power the Pi, join its DigiPi AP (password abcdefghij), browse to http://10.0.0.5/wifi.php, hand it your home Wi-Fi.
5. Initialize — reach it at http://digipi/, open the Initialize page, set callsign and grid.
6. Operate — pick a mode tile and go.

4.7 Platform quick facts

• Recommended host: Raspberry Pi Zero 2 W (~$15). Also supported: Pi 3, Pi 4, Pi 5.
• OS base: DigiPi 2.0 re-based on Raspberry Pi OS “Trixie”; latest Direwolf beta; new GPIO code.
• Image versioning: e.g. “Ver 2.1-3” (mid-2026).
• Caveat: the experimental HDMI-display feature is not compatible with the Pi Zero 2 W (use small GPIO/SPI panels instead).
• Author, docs: Craig Lamparter, KM6LYW — craiger.org/digipi and digipi.org.

Glossary

• Direwolf — Open-source software TNC that DigiPi uses for APRS and AX.25 packet, doing the modulation/demodulation in software; also drives the 2.x APRS map.
• TNC (Terminal Node Controller) — The modem for packet radio; converts data to/from the audio tones the radio transmits. DigiPi’s is software (Direwolf), not a hardware box.
• KISS — “Keep It Simple, Stupid,” a minimal framing protocol that lets external software use a TNC. DigiPi exposes a KISS TNC over serial/Bluetooth.
• IGate (Internet Gateway) — An APRS station that bridges RF traffic to/from the APRS-IS internet backbone (feeding sites like aprs.fi).
• Digipeater — An APRS/packet station that re-transmits received packets to extend network coverage.
• ARDOP (Amateur Radio Digital Open Protocol) — An open HF data modem; on DigiPi it carries Winlink email over SSB on the HF bands.
• Pat — A modern, cross-platform Winlink client with an email-style web inbox/outbox; DigiPi’s Winlink front-end.
• WSJT-X — The reference weak-signal application; on DigiPi its headline mode is FT8.
• rigctld — The Hamlib rig-control daemon; provides CAT (frequency/mode/PTT) control of USB rigs to the mode apps.
• RIB (Radio Interface Box) — A ready-made PTT/keying interface (e.g. the N7EBB RIB) that isolates and switches the radio’s PTT line from a control signal.
• VOX (Voice-Operated Switch) — Sound-activated transmit keying; a poor substitute for a real PTT line because of timing slop and false triggering (see Vol 3).

Sources

• craiger.org/digipi — KM6LYW’s primary DigiPi documentation and build notes (authoritative; confirm prices, versions, and steps here).
• digipi.org — DigiPi project site.
• KM6LYW Patreon — Where the ready-to-flash collective SD image is distributed (from $1); underlying software is open source on GitHub.
• Component apps’ own projects — Direwolf, WSJT-X, Pat, JS8Call, FLDigi, and Hamlib/rigctld each have upstream documentation worth consulting for mode-specific detail beyond DigiPi’s packaging.

4.8 Related reading on this site

• WPSD hotspot and SkyBridge Plus — the DMR/digital-voice hotspots DigiPi is often confused with (they carry their own MMDVM RF hat; DigiPi does not).
• DMR network — the digital-voice network world, for contrast with DigiPi’s data modes.
• AnyTone D878 — a DMR HT (the kind a voice hotspot bridges).
• Baofeng F8HP — a cheap FM HT that pairs with DigiPi (via an AIOC) for VHF APRS/packet/Winlink.
• Xiegu X6100 — a USB-CAT HF rig: the clean single-cable path for FT8/JS8Call/ARDOP-Winlink.

4.9 Verify-on-a-real-unit checklist

Every item flagged TBD — verify across Volumes 1–4, consolidated. Confirm each against a real DigiPi and/or craiger.org before relying on it:

• Supported Pi models — current exact supported-board list and per-board caveats; the “recommended” designation.
• HDMI-display feature — that it remains experimental and Pi Zero 2 W–incompatible; what it actually displays.
• Bundled software versions — Direwolf beta build, WSJT-X (fact sheet: 3.0.1), Pat (1.0.0), JS8Call, FLDigi, ARDOP; and the current SD image version (e.g. “Ver 2.1-3”).
• Patreon gating — current tier/minimum pledge for the image download; whether any free image path exists.
• Direwolf Dashboard — exact name, layout, and controls of the animated APRS map.
• APRS WebChat — addressing, ack handling, bulletins, RF vs IGate send behavior.
• Digipeater/IGate config — how aliases and APRS-IS parameters (server, passcode, filter, RF-gating) are entered; defaults.
• Bluetooth TNC — the pairing flow and that APRSdroid (or named app) connects and passes traffic; rfcomm channel/profile.
• Winlink/Pat — selecting ARDOP-HF vs packet-VHF, gateway/RMS selection, account/password entry; Pat version.
• WSJT-X / FT8 — how the UI is presented over the browser, band/frequency setting, automatic time sync; version.
• JS8Call — launch/presentation and shared CAT/audio config with WSJT-X.
• FLDigi — presentation, enabled sub-modes, and whether SSTV is in FLDigi or a separate app.
• rigctld — how the Hamlib rig ID is selected, device binding, and PTT-method selection (CAT vs GPIO/RIB).
• Type-A USB rigs — per-model USB enumeration (single composite audio+serial vs separate CAT cable) and quirks.
• DRA-Pi-Zero — price (~$75), availability, correct DigiPi-compatible variant, radio-side cabling.
• DigiPi Hat — price (~$40), where sold, feature set (CAT? PTT method), difference from DRA-Pi-Zero.
• Fe-Pi Audio Z v2 — price (~$24–34) and DigiPi compatibility.
• N7EBB RIB — price (~$25) and source.
• DIY PTT circuit — exact reference wiring (2N7000 pinout, GPIO pin, 100 kΩ resistor placement, any isolation/flyback) before soldering.
• Digirig Mobile — DigiPi compatibility, required radio cable, pricing.
• AIOC — price (~$25), connector match to your specific HT, compatibility, any firmware/config.
• GPIO displays — prices (Adafruit 1.3” TFT ~$16, 2.8” ILI9341 ~$45), current support, what each shows.
• Power/enclosure — recommended supply, current-draw figures, enclosure suggestions.
• SD flashing — minimum card size (~8 GB), download/unzip steps, leaving Raspberry Pi Imager customization untouched.
• Default access — AP SSID DigiPi / password abcdefghij, http://10.0.0.5/wifi.php, http://digipi/, and the Initialize page fields.