HOAR4s Defibrillator - (Practice Board)
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- Inventory on the way
Give your DRL Racer4 a new lease on life.
The HOAR4s Defibrillator is a breakout board designed to make the Racer4’s original electronics easier to connect to a conventional receiver and analog video transmitter. It plugs into the connector originally used by DRL’s RF equipment and exposes connections for installing your own equipment.
Why this board exists
When DRL sent practice drones to its pilots, those drones needed to operate without the league’s specialized Race Stack system, which handled video and control connections. DRL provided a similar breakout board so pilots could connect alternative equipment.
The HOAR4s Defibrillator follows that same approach, bringing the connections from the original RF connector out to accessible solder pads.
Available connections
The board provides access to:
- The analog video signal intended for the video transmitter.
- The receiver control connection.
- 5V power and ground.
- Additional UART TX/RX connections mapped to match the original breakout board.
The UART number associated with those additional TX/RX connections has not yet been confirmed. They are exposed to match the original board, but their function and configuration should be verified before relying on them for a particular accessory.
What this board does—and what it doesn’t
This board makes the original connector easier to work with. You will still need to install and configure a compatible receiver and video transmitter.
It does not unlock access to the flight controller’s onboard analog OSD chip. With the analog configuration described here, you will have a camera feed without Betaflight’s on-screen display overlay. It should include the original DRL OSD but it offered very little OSD information.
The exposed power pads provide 5V. Confirm that your receiver and video transmitter support that voltage and that their power requirements are compatible with the available supply.
Is this board required to fly the drone?
No. Depending on your setup, you may be able to connect your equipment directly to the flight controller.
The flight controller has a pad labeled SBUS that can be used with an appropriately configured, compatible receiver. An ELRS receiver must support and be configured for the required SBUS output; simply connecting a receiver running its usual CRSF output will not make it work through that input.
For a basic analog installation, the camera’s video output can be connected directly to the video transmitter. That arrangement also bypasses the flight controller’s analog OSD.
The Defibrillator provides a convenient connection point for a conversion, but it is not the only way to get a Racer4 flying.
What about HDZero?
This board is not required for an HDZero conversion.
My personal preference for a Racer4 that I intend to fly is to install HDZero and update the flight controller with our custom target on the current version of Betaflight. That is a separate conversion path with its own wiring and firmware requirements; installing this breakout board alone does not perform that upgrade.
Who is this board for?
The HOAR4s Defibrillator is for Racer4s owners who want to reuse the drone’s original electronics and need a practical way to connect a conventional receiver and analog video transmitter.
This is a DIY conversion component. Soldering, receiver setup, and flight-controller configuration are required. Choose it with a clear understanding of the available connections and the analog OSD limitation described above.
Firmware & Files:
https://drive.google.com/drive/folders/1eaGZFEpuia18d4xntFWQE_yKxnLlaL5y?usp=sharing
Product does not include a vtx or receiver.
