RC Receivers

Preamble

Following on from RC Transmitters, here is a quick look at the receiver modules.

Receiver Modules

FrSky’s XSR 2.4GHz receiver features 16ch ACCST, with S-Bus and CPPM. This little guy is physically smaller and lighter weight than the X4R receiver. Making it great for mini race quads!

Compatibility
FrSky X-series Module & X9D & X9DP &X9E & X12S in D16 mode. (XSR does not work with D-series Module) The LBT version of XSR receiver only works with FrSky D16-LBT Mode.

Features

Smart Port enabled, realizing two-way full duplex transmission.
S-BUS output. CPPM output.
Lighter weight and physically smaller than X4R.
More number of channels: 1~16ch from SBUS channel,1~8ch from CPPM Channel.
FrSky XSR 2.4GHz 16CH ACCST Receiver w/ S-Bus & CPPM

Specifications

Dimension: 26*19.2*5mm(L x W x H)
Antenna Length: 90mm
Weight : 3.8g
Operating Voltage Range: 4.0~10V
Operating Current: 100mA @5V
Number of Channels: XSR – 16Ch (1~16ch from SBUS Channel, 1~8ch from CPPM Channal)

Also,

Furious Mini RX Receiver 8 Channel for FrSky Taranis FPV Micro Quad Race SBUS

The Furious Mini RX for Frsky is designed for micro quads.

Features :

  • Mini size: 17×24 mm
  • Light Weight: 2.5g (with antenna)
  • Operating Range: 500m
  • S-bus output without inverted (don’t need inverted on FC)
  • 8 channel output
  • Telemetry HUB
  • Input voltage: 4-6V (normal 5V)
  • Compatibility: FrSky Taranis, Taranis Plus, & XJT module

NOTE: Regarding F3 chip, you need go to CLI on cleanflight and set sbus_inversion = OFF >> save

Comparing FrSky receivers, from FrSky X8R, D8R-II Plus & D8R-XP:

X8R:
PWM, sBus, RSSI – unusable, wrong implementation
16 Channel (via sBus)
Smart Port

D8R-II Plus:
PWM, PPM (CPPM, RSSI with 2 and 3 jumpered) – when flashed with D8R-XP firmware
8-Channel
ACCST technology
Data-Stream Port

D8R-XP:
PPM, RSSI, and PWM for ch 5-8
8-Channel
ACCST technology
Data-Stream Port

D8R-XP and D8R-II Plus share the same hardware and so the D8R-II Plus can be flashed, to give D8R-XP functionality, see Difference between D8R-II plus and the D8R-XP ???

d8r-xp

From PPM and CPPM, Can someone explain?

So ppm is quite literally “pulse position modulation”. Its used for signals, and it varies the position of the signal based on the desired value:https://en.wikipedia.org/wiki/Pulse-position_modulation

CPPM is just “combined PPM”, which combines multiple PPM signals onto one channel, which is excellent for multirotors. With planes, normally each channel goes to a servo or combination of servos, so having 5 connections for 5 channels makes sense. However, for a quadcopter, all the channels go straight from the receiver to the flight control board, so requiring 5 separate leads to transfer the data makes no sense, thus CPPM is used so you can have only one cable between your FC and receiver.

The D8R-II plus is a bit strange. You have to flash it with the image meant for the D8R-XP, since the internal hardware is the same, and then if you jump the signal lines of channels 3 and 4 you can use CPPM.

From Flashing Frsky D8R-II Plus for CPPM (27ms),

Ch1 CPPM (all eight channels)
Ch2 RSSI
Ch 3 jumper
Ch4 jumper
Ch5 available
Ch6 available
Ch7 available
Ch8 available

See also FRSky D8R-2 Plus PPM

From Instructables, How to build a ZMR250 racing quadcopter:

I chose the D4R as I have a FrSky DJT module in my Turnigy 9XR. For those with an XJT or internal XJT in their Taranis, the X4R-SB is a better choice as SBus has significantly lower latency and better error handling than CPPM.

There are some clone receivers as well, see FrSky RX SBUS and Frsky DJT Module.

About SBUS

See RC Radio Types: PWM, PPM, SBus, DSM2, DSMX, SUMD

Also, RC radio control protocols explained: PWM, PPM, PCM, SBUS, DSMX, DSM2

See PPM VS SBUS – D4R-II VS X4R-SB, The D4R-II does not support SBUS:

D4R-II is widely supported by most flight controllers without any additional converter or adapter, for both signal or telemetry.

The X4R-SB might require signal inverter for some flight controllers like Naze32 Rev5, or a SBUS-to-PPM converter on the KK2. For using SBUS and Smart Port (S.Port) on Naze32, check out this tutorial.

However on the X4R-SB, it allows you to use the 3 additional PWM channels while running the 16 channels SBUS. So you can hook them up maybe to your servos, gimbals, loud buzzer etc where only accept PWM input. With PPM enabled on the D4R-II, you lose the PWM outputs.

Both RX are similar in price and range (both are marketed range of 1.5Km), binding process and failsafe setup are the same.

Note that SBUS will not work directly with an ArduPilot Mega (APM) flight controller, a SBUS-to-PPM convertor is required, from SBus support:

If you are tying this on APM, it won’t work. There is no sbus support on APM 2.x

What Paul Phillips explained above is for CPPM (ppm sum) connection. You may get CPPM from your Futaba sbus Rx but you will need a s-bus to CPPM converter like this

It is a very affordable device and it works. I used that with my Futaba 3-channel R6303sb Rx. So if you use this converter between APM and Futaba Rx, plug it into APM’s Ch1 and jumper the signal pins on ch2 and ch3 of APM, it will work.

You cannot plug an sbus into APM directly.

Although, it appears that there is a new firmware, see also ArduPPM sbus support.. I’m confused


See also, PPM/PWM from FrSky D4R-II simultaneously?

#define SERVO_TILT (this will enable switch controls via the camera stabilization pins on the FC. We can use the pitch channel – nanowii pin A0)

#define TILT_PITCH_AUX_CH AUX2 (change from default setting AUX3 seeing as your rx only outputs 6 channels)

Hook up the receiver controlled switch signal wire to the nanowii pin A0.

Do NOT enable CAMSTAB from the gui (otherwise pin A0 will revert to pitch stabilization instead of a switch)

Assign a radio switch to drive AUX2 channel

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