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 the Spektrum Satellite receiver, 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.

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:

– Standard 3-pin Spektrum Satellite cable, to be cut in two parts
– Molex 5-pin connector housing, Molex P/N 51021-0500 (Mouser 538-51021-0500)
– Three Molex picoblade wires, Part number 79758-0006 (Mouser 538-79758-0006)
– Small length of heatshrink suitable for the single wires

The basic concept is that instead of feeding PPM into the connector on the Vortex PDB, the serial output from the Spektrum is fed into the GPS port. Since the Spektrum requires 3.3V instead of 5V, the GPS port’s power is used also.

The cable should be built following the diagram below. To avoid having to crimp these tiny connectors without the appropriate tool, it is highly recommended to simply splice together the cut spektrum cable, with the picoblade wires listed above. Ensure that the splice is protected with a piece of heat-shrink, to avoid shorting against the carbon fiber frame.

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

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

2) Remove the standard PPM cable from the Vortex, remove the right side-plate, and install the cable into the GPS connector. Route the cable through the rubber-grommet and into the Spektrum satellite, which fits nicely on the tail end of the Vortex

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 the receiver type. For DSMX receivers (the most common case these days), select SPECTRUM2048.
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.

6) Reverse the AIL and RUD channels on the Spektrum Tx

7) Change the Travel on the Spektrum Tx to +/- 148, as opposed to the standard +/- 100

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

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

NOTE:
Instead of configuring the Spektrum transmitter manually, a file is available Download (2.4 KB) here which can be used to load the model into any recent DX6 or newer.
To do this:
1) Extract the downloaded file onto the root of an SD Card, and insert it into the radio

2) Enter the System Setup menu

3) Enter the Transfer SD Card menu

4) Select the Import Model option, and select the VortexGPS.SPM file.

Executive Summary

  • The above procedure documents how to directly connect a Spektrum Satellite receiver to a Vortex, to create a very low-latency link
  • Average latencies of ~15ms are possible with this link, from stick movement to flight controller response
  • Until an off-the-shelf cable is available, some soldering skills are required to make the cable