FrSky R9 Slim Specifications


As shown in the FrSky R9 Slim manual, this receiver which has similar specifications to the previous R9 receiver is much smaller and lighter (Dimensions: 30*13.5*5mm (L×W×H) & Weight: 3.2g), it can reduce the output latency, and it supports the redundancy function, or the master and slave receivers which receive SBUS signal from the slave receiver. This means you can add another receiver as a back-up in case the first one fails. And the firmware on it can also be updated to the last version.




Its operating range it's up to 10 Km or above, which along with the telemetry makes this receiver very suitable for long range purposes. According to the FrSky R9 Slim Manual, the receiver also has an analog RSSI output. It can operate between 3.5V up to 10V and its current draw on 5V is only up to 100mA. And it is only compatible with the R9 transmitter modules series, so if you have an R9 module and a radio transmitter with a module bay you will be able to get this receiver working.


FrSky R9 Slim Features


This small and convenient receiver works on a 900 MHz frequency in the Non-EU Version and on a 868 MHz frequency on the EU version. It supports Smart Port to enable telemetry data transmission to a flight controller or to any other device along with battery voltage detection to notice sudden battery drops during the flight. And as you can see in the FrSky R9 Slim Manual, the PCB of the receiver is covered on conformal coating to protect the electronic components on it.




FrSky R9 Slim Wiring Diagram


The R9 Slim pinout it's divided in two parts, the top part with 6 pins and the bottom part with eight pins for servo outputs. Let’s check every pad according to the next diagram shown in the FrSky R9 Slim Manual.




⦁    S.PORT: The S.Port or Smart Port is a two-way full duplex transmission of telemetry protocol used by FrSky which allows you to get the telemetry information of the model such as battery level, RC signal strength, etc. But it also allows you to connect other sensors which you might need for your aircraft.

In flight controllers it must be connected to the TX pad of a free UART, and it also needs to be set up in the flight controller configurator. Most F4 flight controllers won’t be compatible with S.Port  because in this receiver there isn’t any un-inverted S.Port output. You can see where it's located on the FrSky R9 Slim Manual diagram.


⦁    GND: The GND must be connected to a GND pad, the negative, of the source from where it is being powered, it is usually recommended to find a voltage regulator in the flight controller and connect both GND pads together. You can see where it's located on the FrSky R9 Slim Manual diagram.


⦁    Voltage pad or FCC: The voltage pad is an input and output used to power the receiver and the peripherals connected to it, it can take from 3.5V up to 10V. It is recommended to connect it to a 5V power supply as many hardware such as servos usually only work on 5V. Only one FCC pad is necessary to supply the receiver, but its power supply must be powerful enough to manage the current loads.  You can see where it's located on the FrSky R9 Slim Manual diagram.


⦁    CH: The channels pads are PWM analogue outputs, each channel corresponds to the pad with its number written. For this reason, this receiver can be used also in models that doesn’t require any type of processed signal, mostly any airplane that doesn't need any type of stabilization mode.  You can see where it's located on the FrSky R9 Slim Manual diagram.


⦁    RSSI Out: This means “Received Signal Strength Indicator” measured in decibels (dB), between the couple of a paired receiver and transmitter and is used to avoid fail safes, the value can be broadcasted to the transmitter, so you are able to know the value almost instantly from ground.  You can see where it's located on the FrSky R9 Slim Manual diagram.


⦁    SBUS Out: SBUS is a digital communication protocol compatible with this receiver. It supports transmitting up to 16 channels and all the signal information can be sent by one cable which can send as many signals as channels have the transmitter. This is quite beneficial for aircrafts with flight controllers to the user comparing it to PWM, which needs a dedicated output for each channel. The downside of this is that you need something to decode the signal in order to have individual channels such as the already mentioned flight controller.  You can see where it's located on the FrSky R9 Slim Manual diagram.


⦁    SBUS In: The SBUS in pad is made for the redundancy function, which allows a redundant receiver to be paired with another receiver so that one will act as a backup to the other one in case of failure. For example, if the master receiver goes into failsafe mode because of low signal, the output signal from the slave receiver will be used until the master receiver exits the failsafe mode.

In order to set this function working, the slave receiver SBUS out pad, must be connected to the SBUS in of the master receiver so that this one can output the signal of the backup receiver by its SBUS out pad in the case that this master receiver fails.  You can see where it's located on the FrSky R9 Slim Manual diagram.