DarkFlippers/unleashed-firmware

[Sub-Ghz] Fails to replay Manchester-encoded Volpe doorbell signals at 310, 325, 433 MHz

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#910 opened on Jul 15, 2025

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bughelp wanted

Description

Describe the bug.

Description

There is a wireless Volpe doorbell that I tested at 325 MHz and 310 MHz, primarily at 325 MHz.

When using the Flipper to capture raw data via Read Raw, it fails to replay them: the signal is Manchester-encoded and is static rather than dynamic.

I also tried with ProtoView, but it doesn’t always trigger.

For comparison, I have another no-name doorbell using Princeton 24 bit; it was detected correctly and everything works fine.

I examined the transmissions in URH and found that the difference between the Volpe transmitter and the no-name transmitter is that the Princeton 24 bit (Nameless_door) alternates zeros and ones.

How can this be fixed for doorbell Volpe? Please let me know if you have any time to help.

I don’t have a full SDR to analyze it as with a HackRF—only an RTL2832U TV-tuner dongle.

P.S: The “Unknown” files are those saved via ProtoView; the “Raw” files come from Read Raw.

Download File: SubGhz_Doorbell_Volpe

Reproduction

Steps to Reproduce

  1. Power on Flipper Zero with the latest firmware.
  2. Navigate to Sub-GHz → Read Raw.
  3. Select Frequency: 325 MHz (repeat for 310 MHz if desired).
  4. Press Record, then press the Volpe doorbell button.
  5. Save the captured .raw file.
  6. Navigate to Sub-GHz → Replay Raw, select the saved file, and attempt to transmit.

Expected Behavior

  • The Flipper Zero should demodulate or at least faithfully replay the recorded Manchester-encoded pulses, causing the Volpe doorbell chime to activate.

Actual Behavior

  • The replayed signal does not trigger the doorbell.
  • In URH analysis, the Volpe file shows a static Manchester pattern (no alternating bits), whereas the Princeton 24-bit file alternates zeros and ones.

Environment

  • Device: Flipper Zero

  • Firmware Version: Unleashed 0.81

  • Recording Method:

    • Raw files captured via Sub-GHz → Read Raw
    • Unknown files captured via the ProtoView app

  • SDR Hardware: RTL2832U TV-tuner dongle (no HackRF or full SDR available)

Additional Information

  • The “Unknown” files are saved through ProtoView; the “Raw” files are saved via Read Raw.
  • URH (Universal Radio Hacker) was used to compare Manchester encoding patterns.
  • The Princeton 24-bit doorbell (Nameless_door) alternates zeros and ones and works without issue.

Can someone advise how to adjust the Flipper Zero settings or firmware to properly record and replay static Manchester-encoded signals shorter than the typical 63 µs pulse duration?

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Contributor guide

Tech stack
c
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C programmingFlipper Zero firmware developmentManchester encoding basicsSub GHz radio concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Investigate the Sub GHz protocol stack in the firmware, specifically the raw replay functionality. Analyze the captured raw files from the issue attachment to understand the Manchester encoding pattern. Compare with existing Princeton 24 bit implementation. Look at files like `subghz protocol.c` or `subghz raw.c` to adapt pulse width detection for static Manchester signals.