RC radio receiver


To connect the receiver on VRBRAIN5  you have three options:

SBUS (or Taranis SBUS), PPMSUM, standard PWM (one cable per single channel)

Note that with VRBRAIN5 we encurage the use of either PPMSUM or SBUS as the input method.

PPMSUM is more common and is used in Graupner radios, and in most thrid party futaba and taranis receivers. It is able to transfer 8 channels on a single wire.

SBUS is a Futaba (and now also FRSky) communication protocol that allows you to send up to 18 channels using only one cable.

Note that at the moment SBUS2 is not supported, please choose SBUS1 for communication with VRBRAIN.

1. Connecting futaba SBUS or PPMSUM (or  FrSky SBUS).

Hardware revision 5.2


On the revision 5.2 the SBUS and PPMSUM connections have changed. This is to help user with a more easy connection.

PPMSUM is now located on the 8th input PIN and has to be connected into vertical with 5V in the center and GND on bottom

SBUS is now located on the bottom rail and can be conencted without splitting the cable. Signal is on the 6th bottom pin, 5V on the 7th and GND on the 8th

Hardware revision 5.1


To connect the SBUS receiver, you need to connect receiver signal cable to the 5th INPUT pin, and connect the 5V and GND to the PINS 1 to 4 as shown in the picture.

Beware, the middle pin of the INPUTS 5,6,7,8 do not have the 5V! They are used for CAN BUS and I²C. You need to get the 5V from the central pins of the INPUTS 1-4

PPMSUM input is located on the 7th INPUT  pin. As for SBUS you need to collect the 5V. from the INPUTS 1 to 4.


2. Connect all 6 PWM inputs.


To use standard PWM, you need to upload a special firmware to the board.

Download this zip file https://github.com/virtualrobotix/VRX_binary/archive/master.zip, unzip and locate the folder “custom”.

For a Copter it would be in:  VRX / firmware / Copter / custom / PPM /

For Plane it will be in: VRX / firmware / Plane / custom / PPM /

 Choose your preferred platform and upload using the instructions below.
  1.  Open Mission Planner, go to Initial Setup–>Firmware
  2. Click on Upload custom firmware and select the file you have chosen in the “Custom” folder
  3. Wait for upload of firmware


To connect the receiver you have three options:

1. Connect futaba SBUS (or Taranis) to the appropriate 3 pin connector.

2. Connect PPMSUM on the 7th INPUT channel

3. Connect all 8 inputs using the the connector provided.

VR μBrain 5.1

With firmware 3.2 PPMSUM is on first input:


Starting with firmware 3.2.1 PPMSUM is on 7th input:


VR μBrain 5.2

VR μBrain 5.2 have the same hardware of 5.1 but with different management. The main difference is about the two connectors “ESC SERVO” and “RC RADIO”. With this new configuration this two connectors are switched.


  • OUT. Looking at the connector from the front, from left to right, the pinout is:
    1. 5V
    2. GND
    3. PWM OUT 1
    4. PWM OUT 2
    5. PWM OUT 3
    6. PWM OUT 4
    7. PWM OUT 5
    8. PWM OUT 6
    9. PWM OUT 7
    10. PWM OUT 8
  • IN: Looking at the connector from the front, from left to right, the pinout is:
    1. 5V
    2. GND
    3. ANALOG INPUT 1 (defined as default for IBAT – pin reference for APM Parameters is 1)
    4. ANALOG INPUT 2 (pin reference for APM Parameters is 2)
    5. ANALOG INPUT 3 (pin reference for APM Parameters is 3)
    6. PWM OUT 9
    7. PWM OUT 10
    8. PWM OUT 11
    9. DIGITAL SWITCH (pin reference for APM Parameters is 33)
    10. PPMSUM
Please note that at the moment you either have a firmware that supports PPMSUM and SBUS or PWM.At the moment of writing there is no way you can have the firmware for PWM and PPMSUM at the same time.

Here is an exemple to show how we connect the Fr-sky x8r receiver to the VR Micro Brain:



Using PPM (standard radio)

Connect your RX to VR Brain board using male to male servo cable


Connect RX channels according to  pin out

rxconnUsing PPMSUM (CPPM)

VRBRAIN is able to decode PPMSUM signal.

PPMSUM is a special signal used by modern radios where the 8 (or more) channels are serialized over one single channel.

This is very useful to limit the number of cables and it will allow to free up 4 input/outputs for general use.

To enable PPMSUM connect INPUT_CH2 and INPUT_CH3 signals with a Jumper.

CH1 will then be used for PPMSUM.

The software will autodetect PPMSUM and enable it in the code.


Please be aware that if you use Futaba and FrSky receivers with CPPM (PPMSUM) output like the TFRSP or TFR4 you MUST disable all Failsafe functions in the radio otherwise there will be terrible jitters and spikes.


Using SBUS – Available from firmware 3.1.16

From release 3.1.16 of VRBRAIN firmware we support SBUS as a communication protocol.

SBUS is a serial communication typical of Futaba radios. It supports up to 18 channels and is very powerful.

VRRBAIN 4.x needs a special cable to convert SBUS protocol in standard serial protocol.

To enable SBUS place a jumper on INPUT_PIN7 and INPUT_PIN8. This will enable SBUS and allow you to have extra 4 outputs on input pins 1-4

These will be seen as channels 9-12 on Mission Planner.


For this reason if you want to try out SBUS on VRBRAIN 4.x boards you need to create your own cable or buy something like this:



Next board release VRBRAIN 5.x will  not need this cable as it will have the transistor on the board.

To make your cable you need:

1. BC547 transistor

1. 10K resistor

1. 1k resistor

1. small breadboard

Once you have this material, cut a standard servo 3 wire in half and connect the cables following this scheme:



This is how it should look like:



Channel order

On Futaba receiver connect the SBUS to SBUS not use SBUS2

Channel order will be:

1-  Roll – required
2-  Pitch – required
3-  Throttle – required
4-  Yaw – required
5-  Flight mode (2 to 6 position) – required
6-  Tune knob (used for tuning and for variable parameters) -optional
7-  Option channel -optional
8-  Option2 channel -optional 

  • CH5 must be configured to enable 6 positions. Usually this is done with channel mixing.
    This channel will be used to change flight mode.
    Please refer to the APM wiki (click here) to have details on different flight modes and channel use.
  • CH6 is generally used for changing parameters on the fly. This enables a fine tuning of the different parameters of the copter (plane). PLease refer to this wiki for more details: In Flight tuning
  • CH7 and CH8 can have different behaviours and generally are used for special functions like Simple, SuperSimple, RTL and so on. Please follow this link to know all features availble for CH7 and CH8


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