This is where the FrSky RXSR Receiver comes in. At a smaller form factor, it provides the same full-range diversity feature as the XM+ but at the same time also provides you with an S.PORT pin to allow for telemetry back to your transmitter.

Let us dig deeper into this receiver and its functionalities.

 

FrSky RXSR Receiver 

The FrSky RXSR long range receiver is a very tiny, full-range receiver from FrSky that has all the capabilities of their XM series receivers but with extra S.PORT telemetry.

The RXSR is basically a smaller version of the ever-popular XSR receiver with a smaller form factor and still keeps the full-range capability.

The RXSR is the smallest receiver from FrSky that can do full 16CH SBUS along with Smart Port telemetry. This is currently the de facto choice for FrSky receivers in mini quads since it is small and provides all the features necessary for racers.

You can get your own FrSky RXSR from HorusRC for 20$

 

Specifications & Features

  • Dimension: 16*11*5.4mm (L*W*H)
  • Weight: 1.5g
  • Number of channels: 16CH
  • Operating Voltage Range: 3.5V~10V
  • Firmware Upgradable
  • Compatibility: ACCST D16 / ACCESS mode
  • Small size and lightweight
  • Telemetry support with S.PORT
  • Full range
  • Switchable SBUS/ CPPM signal output
  • Supports redundancy function
  • IPEX connector, replaceable antennas

 

Redundancy

The RXSR features a redundancy feature that helps you connect two receivers in a master-slave configuration. What this enables is that even if you lost range with your master receiver, your slave receiver could function normally and thus keeping you in control of your craft. This is a neat function when you are doing long-range flights and helps you to prevent micro failsafe.

The only drawback would be that you would require two separate transmitter modules to connect to each receiver. One receiver (master) would be bound to your internal XJT transmitter on your FrSky radio while the slave receiver would be connected to an external XJT module on the same radio or you can even use a separate radio to control it.

Due to the sheer complexity and extra costs involved in using this, it is only useful for long-range pilots and not racers or normal freestylers. If you get frequent fail-safes, I would recommend investing in a long-range module such as the FrSky R9M.

 

Connecting to your Flight Controller

In a previous article, we have seen the wiring of the FrSky XM+ receiver. It is a similar method for the RXSR receiver as well.

Unlike the XM+, the RXSR comes with a connector to for the receiver to connect your signal and power wires, so it makes wiring slightly easier.

Connect the SBUS wire to your SBUS in pad of your flight controller ( do not connect the “SBUS input” wire from the RXSR for this, this wire is for the redundancy connection).

To power your receiver, you should also connect the 5V and GND pins to their respected pins on your flight controller. This is enough to get your receiver powered and providing SBUS signal to your flight controller but if you also require telemetry function, you will need to connect the S.PORT pin to a free UART RX pin on your flight controller.

If you are using an F3/F4 flight controller, you would not be able to use S.PORT wire directly from your RXSR receiver, this is becasue F4 and F4 boards only have one hardware inverter and cannot take in the inverted S.PORT signal from your receiver.

FrSky was kind enough to break out the uninverted S.PORT pad on the RXSR. You should solder a small wire, very carefully to that pad and to a free UAR RX pin on your flight controller to get S.PORT working.

The above picture shows the pads for the uninverted S.PORT pad and even the pad for the uninverted SBUS pad in case you ever require that as well.

The FrSky RXSR Receiver is undoubtedly one of the best receivers FrSky has ever launched as it packs a lot of features ina tiny form factor. It has become my de facto choice for mini quads and even micro-quads because it is so small that it can fit in whoops as well!

The RXSR is one receiver I could recommend without a second thought and as an added bonus, the receiver is also capable of upgrading the new ACCESS protocol which will enable OTA updates as well!