The stock Vortex 285 has support for PPM receivers, with a single-wire CPPM input.

An accessory will be available shortly which interfaces directly between S-Bus compatible receivers, and the PPM connector on the Vortex.

For users who wish a lower-latency connection, without the addition of an external adapter, this document should be of interest.

A custom cable is required for this hookup, but it is fairly simple to put together for anyone with some basic soldering skills.

Note that S-Bus serial data is inverted. This document assumes the use of an FrSky X4R-SB receiver which can easily be modified to remove the inverter.

This procedure does require the use of the GPS port on the Vortex 285, a port reserved for future accessories, but currently unused.

The following parts are required:

– Modified FrSky X4R-SB Receiver (the black one)
– Standard Vortex PPM Cable
– Molex 5-pin connector housing, Molex P/N 51021-0500 (Mouser 538-51021-0500)
– Single Molex picoblade wire, Part number 79758-0006 (Mouser 538-79758-0006)
– Small length of heatshrink suitable for a single wire

The basic concept is that instead of feeding PPM into the connector on the Vortex PDB, the serial output from the S-Bus receiver is fed into the GPS port (center pin).
Since the GPS port supplies 3.3V, and the PPM connector on the PDB supplies 5V, the power for the S-Bus receiver will be drawn from the PPM connector.

Modifying the X4R receiver is fairly simple. Remove the outer cardboard case, cut the pin shown in the photo below, and bridge it to one of the 4 small connector holes (third hole from the servo connectors).

Once the cable has been built, the following steps should be followed:

1) Bind the FrSky receiver with the R/C Transmitter before connecting it to the Vortex

2) Plug the modified PPM cable into the Vortex. To do this, remove the right side-plate, install the PPM cable, and thread the single serial wire through to the GPS connector.
Ensure that this rather fragile wire is protected against being caught in the folding-arm mechanism (sticking the wire to the PDB with thin double-sided tape works pretty well).

3) Install the ImmersionRC Tools, version v1.42.4.

4) Using the tools, upgrade the firmware in the Vortex to v1.0.0.21.

5) Cycle power to the Vortex, connect it via USB to a PC, and use the Cleanflight Configurator to upgrade the flight controller firmware to v1.10.0.

6) Cycle power again, connect the Vortex to the PC, and on the Vortex page of the ImmersionRC Tools, select S-Bus as the receiver type.
NOTE: Once the receiver type is changed here, the wizard will no longer automatically recognize PPM receivers. This will be automated as soon as a required patch is installed into CleanFlight.

7) Map channel 5 to a 3-position switch (we use Switch E) to control flight mode (Acro/Level/Horiz).

8) Run through the wizard in the normal way, to teach the Vortex about the channel assignments, and stick mode, of the R/C Tx.

The standard Taranis center, and endpoints may be used with this S-Bus connection through the X4R. No changes are required.