ESP32-C5 Analog 5.8 GHz FPV Receiver

From live 5.8 GHz FPV video to real-time analog CVBS with one Seeed Studio XIAO ESP32-C5 and a passive resistor DAC.

C5VRX-5 receives analog 5.8 GHz FPV video using the ESP32-C5's own radio and outputs composite PAL/NTSC through a passive 6-bit resistor DAC. It includes automatic gain control, startup calibration, an on-screen menu and browser-based flashing and controls. The sync flywheel was removed on 2026-10-25 (it caused severe desyncs and poor range on the board).

This branch builds and boots U80P64-R1 only. U85Q, kp/LP switching and m/K/k/j/P/O/H controls are retired; see P64 integration and evidence. The fixed R1 table has one positive NTSC observation; PAL, weak-signal/range and the final cleanup still need hardware validation. This default is an operator choice, not a hardware qualification claim.

The PR #254 11p receive baseline is now applied at startup and after channel/bandwidth/AFC restores, before measured analog profiles and digital mode 0. Upgrading discards earlier RF calibrations; let startup calibration finish (VTX off is best). The noise-only bench result is not a measured sensitivity/range gain; see 11p integration and limits.

• Test every new firmware version and hardware/settings combination on the ground first. Remove propellers for bench tests. Check startup and calibration, weak-signal behaviour, recovery after video loss, and your actual camera/goggles. Complete calibration before takeoff.
• Keep disruptive controls on the ground: calibration, scanning, channel changes, menu entry/exit, DAC tests and diagnostics can interrupt or replace the live picture. Do not flash firmware or run bench tests during flight.
• Automatic changes are experimental too. Live filter/profile switching is currently documented as enabled by default and awaiting board validation. It restarts part of the receive chain and may interrupt video. Console A disables live profile switching (report-only mode); confirm the state with T on your build. Live OUTPUT, format and profile changes restart the pipeline. These settings do not establish flight safety.
• If you proceed to flight testing, use a controlled area clear of people, traffic and property, keep the aircraft close, and have a safe way to recover control if video disappears. Follow applicable local rules, including visual line-of-sight and observer requirements.
• A versioned release, a “Latest” label or passing CI is not flight qualification. Unmerged PR builds are development builds. Check the exact build's documented hardware and flight-test evidence; a test of an earlier build does not validate later changes.
• Report unexpected video loss with the exact firmware version/commit, hardware, settings, reproduction steps and any available logs/DVR footage. Preserve evidence after an incident, and investigate on the ground before flying again.

The firmware is provided under GPL-3.0-only, including its warranty and liability provisions in sections 15–17, to the extent permitted by applicable law. This warning does not replace those terms or limit rights that cannot legally be excluded.

Watch the C5VRX-5 vs C5VRX-4 flight range test by Louis Hitchcock.

XIAO ESP32-C5. DAC on D4..D9 (GPIO 23, 24, 11, 12, 8, 9; LSB first) with 8.2k / 3.9k / 2k / 1k / 470R / 240R and a 200R load, as in C5VRX-3/4 (schematic). The receiver uses the ESP32-C5's own Wi-Fi radio; no extra RF parts.

Six resistors, one per XIAO pin, all joined on one node: that node is the video output (CVBS). A seventh resistor from that node to GND is the load.

D4 --[8.2k]--+
D5 --[3.9k]--+
D6 --[2.0k]--+
D7 --[1.0k]--+-----------> CVBS out (goggle / monitor AV-in, video)
D8 --[470R]--+     |
D9 --[240R]--+   [200R]   (optional: 470 pF from the node to GND,
                   |        improvement unproven)
GND ---------------+------> GND (goggle / monitor AV-in ground)

• The pin order matters: the largest resistor (8.2k) goes on D4 and the smallest (240R) on D9. A swapped pair gives a scrambled, banded picture.
• Connect the output node to the video input (centre/tip) of the goggles, a DVR or an analog monitor, and the XIAO GND to its ground. A common ground is required.
• All values are standard E24; 1 % metal-film resistors are fine. Keep the wires from the pins to the node short.
• Too dark or too dim on some goggles: try OUTPUT in the menu (0.5-5.0x, saved). Higher levels can clip; check the loaded output on your display.
• The XIAO is powered over USB-C or its 5 V pin as usual; the DAC needs no separate supply.
• Check the build with the DAC self-test before chasing picture problems: a test pattern for the goggles and a multimeter check that names a swapped, open or wrong resistor. See Building and testing the resistor DAC.

If you prefer a clean PCB over perfboard, the open-source C5VRX_JACK_DIY carrier board is designed to drop directly into standard Fat Shark goggle bays while also including a 3.5 mm TRRS AV jack for universal bench testing and standalone monitor hookup.

Getting the PCB manufactured (via JLCPCB, PCBWay, etc.) is extremely inexpensive—often even cheaper than buying a sheet of perfboard—and only requires soldering standard through-hole ¼W resistors and pin headers!

• Browser: open the web flasher in desktop Chrome or Edge, choose C5VRX-5 and a build, then flash. Use Full firmware when switching from another generation. Unmerged PR builds are marked as development builds.
• From source: use ESP-IDF 6.0.2 and run idf.py build flash in the repository root. Filter and DC correction require its exact libphy; other PHY versions disable them and produce a build warning.
• Local File flashes your own .bin; Legacy builds contains archived C5VRX-3 firmware.

1. Power the receiver with the VTX off and let calibration finish. The goggles show progress; the first run can take up to eight minutes. Results are stored, so later boots skip completed measurements. A firmware update may require a fresh calibration.
2. Turn on the VTX and select its channel or use SCAN. Without a stored channel, the receiver starts on A1 (5865 MHz).

The menu provides BAND, CHANNEL, SCAN, VIDEO (AUTO/NTSC/PAL), CALIBRATE, OUTPUT (0.5-5.0x), GAIN (AUTO/MAX/fixed), DAC TEST and EXIT. It closes after 30 seconds of inactivity, or five minutes in DAC TEST. Menu transitions can interrupt video. GAIN starts in AUTO on every boot.

Use the web flasher's Terminal tab for receiver controls and logs, or a serial terminal at 115200 baud. Keys are case-sensitive and sent without Enter; h lists the commands supported by your firmware.

P64 always uses the same fixed program and LUT. Profiles select only the analog filter (DEFAULT, NARROW or WIDE); old kp_auto and lp_cn settings are ignored. A toggles experimental live profile switching (default on). Live OUTPUT and profile changes share a five-second cooldown and verified halted restart/rollback. Higher OUTPUT levels can clip. GAIN always starts AUTO at boot; the OUTPUT preference is saved. Check T after changing settings. Retired models remain research only.

The browser terminal and flasher use the port one at a time. Download log saves the displayed output; only the latest 120,000 characters are retained.

• DAC build and self-test guide
• C5VRX_JACK_DIY Fat Shark carrier PCB
• Receiver findings and hardware evidence
• Field-test protocol
• Current receiver changes and validation
• U85Q research and research index
• Contributing

main/ contains C5VRX-5 firmware, web/ the GitHub Pages flasher, test/ host tests, docs/ guides and findings, research/ experiments, and tools/ console and CI helpers. legacy/ preserves C5VRX-1 through C5VRX-4 as reference; they are not built.

CI runs host/research checks and builds firmware with ESP-IDF 6.0.2. Firmware changes publish versioned c5vrx5-v5.0.N releases or unmerged c5vrx5-pr-N builds. Website-only changes do not create firmware releases. Pages deploys the website from main with a same-origin firmware mirror. Firmware PRs need passing checks and board tests on the matching artifact; host tests alone do not establish picture compatibility or RF range.

Share build photos, questions and feedback on the C5VRX Discord.

C5VRX-5 is part of C5VRX by Twotoz and the C5VRX contributors; the official website (twotoz.github.io/C5VRX) has the project and its Discord invite. It builds on C5VRX-2..4 (the continuous MODEM_DIAG to BitScrambler video path, Direct Gain V3-V5, the PAIR schedule and the U85Q study of PR #190), on zerowidth/C5VRX PR #3 (interference-burst gate, sampling-phase probe, off-grid channel tuning), on Louis Hitchcock's staged overload recovery (C5VRX #182/#184), and on ESPARGOS esp-sdr (GPL-3.0) for the C5 RX filter control. Espressif supplied the GDMA EOF fix (espressif/esp-idf#19091).

Like the rest of this repository, C5VRX-5 is licensed under GPL-3.0-only (see LICENSE). The GPL allows commercial use, including selling receivers with this firmware, provided the source (with your changes) is passed on under the same license.

The C5VRX name and logos have separate terms; see assets/BRANDING.md.

Product	Photo	Link / Source
Seeed Studio XIAO ESP32-C5		View on Amazon
C5VRX_JACK_DIY Carrier PCB		Gerbers & KiCad files (often cheaper than perfboard!)
Perfboard (alternative)		View on Amazon
Resistor kit		View on Amazon

Affiliate links. As an Amazon Associate, I earn from qualifying purchases. All affiliate earnings go back into C5VRX development.