Some time ago we were reviewing a couple of the best F3Evo-based flight controllers from FrSKY company with intergrated FrSKY receivers: XSRF3E and XMPF3E. Those controllers are brought to market in a strive to save some racing quads weight and deliver the ease of setup. Not only they have inbuilt FrSKY receivers but also provide most of the features original SpRacing flight controllers offer. Moreover, the reviewed samples were used to build same 210 racing quads and are still working perfectly.
Today, we would like to introduce and review new FC from FrSKY — XSRF3O:
As it is understood from its name — this FC has FrSKY XSR intergrated receiver with S.PORT telemetry downlink and is based on SpRacing F3 flight controller with most of the features from both manufacturers. One would say that building new FC’s on F3 now is kind of outdated… especially if the previous controllers were based on F3Evo boards… and most of the sports pilots now choosing F4 or even F7 controllers… But I would not agree. Why? Because:
- When you are a newbee — F4 or F7 is not so vital
- F3 is the most reliable and stable due to long market availability
- F3 flies great and very easy to tune
- F3 is enough for those pilots who are not only competing but mostly flying for fun
But what is the difference to the previous XSRF3E and XMPF3E FCs that FrSKY developed?
- Onboard BetaFlight OSD
- Some more general MPU6050 Gyro with I2C BUS
- Onboard blackbox and SDCard slot
- No race transponder pins
That is it. So, let’s say that current FrSKY F3 based boards with FrSKY receivers would be used for different applications:
- XSRF3E — when you want 8/8KHz gyro and PID loop rate + XSR receiver + telemetry
- XMPF3E — when you want 8/8KHz gyro and PID loop rate + XMP receiver + SDcard for blackbox and external OSD
- XSRF3O — when you want 4/4KHz gyro and PID loop rate + XSR receiver + telemetry + BetaFlight OSD + SDcard for blackbox
Anyway, all of those boards help a lot to maintain the weight of the racing quad low and have less cables and soldering to deal with.
My 210 racing frame setup (with detachable arms) weights only 288g with this FC.
XSRF3O tech specs:
- STM32F303 CPU – F3 Processor
- MPU6050 Gyro with I2C BUS
- Betaflight OSD
- FrSKY XSR receiver with S.Port telemetry
- Built in MicroSD card slot for BlackBox
- Operating Voltage Range: 4-10V
- 36x36mm (30.5mm mounting holes)
- 7g weight
- 1-8 PWM outputs (1-4 outputs are situated in the corners of the board)
- LED strip pads
- Buzzer pads
- S.PORT pads
- OSD pads (camera + VTX)
- Current pad (to be used with external current sensor)
- Battery voltage pad (direct soldering from raw batt voltage)
- FC boot button
- XSR bind button
- SDcard slot for blackbox
So, having all those features we can build a modern racing quad with excellent radio receiver, telemetry downlink, OSD function, blackbox logging, buzzer, programmable LED strip… And all of that would be driven with 4|4KHz gyro and PID loop rates which is totally enough for the most of the pilots.
In the box:
Box contents include the board itself, a set of soldering pins and instruction manual.
Initial BetaFlight configuration:
The board comes with 3.2.0 BF FW and preconfigured to work with BetaFlight configurator available as a Chrome browser applet (use Chrome shop to locate it). The board should be called FrSKY F3 on Betaflight configurator FW update tab.
The main settings that differs this board from SpRacing F3 are the following:
- UART2 should be set to SerialRX
- UART3 should be set to SmartPort
- Receiver mode should be RX_SERIAL
- Receiver provider should be SBUS
- RSSI channel should be 8
Other settings should be set according to your liking. Nothing new or strange.
Due to the fact that this board has full telemetry — we can use PID tuning LUA scripts on our radios (X9DPlus, X7, X9D, Horus X12S, etc). Moreover, we can change PIDs using usual BF OSD menu (throttle stick to the left and elevator stick up to access OSD menu + throttle stick to scroll and aileron stick to activate|diactivate setting) .
XSR receiver FW upgrade could be done using dedicated S.PORT pins on the board. But the FW version for the receiver is not the same as for the usual XSR. This integrated receiver version has its own FW that can be located on the FrSKY website.
There were some minor flaws in the XSRF3O tuning with BetaFlight configurator due to the current FW development of the board. But by the time it would spread on the market — FrSKY would eliminate all the smaller issues.
Easy. Just solder signal video cables from camera and VTX to the dedicated pads on the board, enable OSD in the BF configurator and you can set all the infomation you want on the OSD tab. Nothing strange there. This is a general BetaFlight OSD menu and setup procedure.
The following sensors are transmitted back to the radio (partially taken from here):
- RSSI — seems to be sent directly to radio from receiver. Even with RSSI switched off on the F3Evo board — we still see the value.
- A4 : average cell value. Warning : unlike FLVSS sensors, you do not get actual lowest value of a cell, but an average : (total lipo voltage) / (number of cells)
- Alt : barometer based altitude, init level is zero.
- Vspd : vertical speed, unit is cm/s.
- Hdg : heading, North is 0°, South is 180°.
- AccX,Y,Z : accelerometers values.
- Tmp1 : actual flight mode, sent as 4 digits. Number is sent as (1)1234. Please ignore the leading 1, it is just there to ensure the number as always 5 digits (the 1 + 4 digits of actual data) the numbers are aditives (for example, if first digit after the leading 1 is 6, it means GPS Home and Headfree are both active) : 1 is GPS Hold, 2 is GPS Home, 4 is Headfree, 1 is mag enabled, 2 is baro enabled, 4 is sonar enabled, 1 is angle, 2 is horizon, 4 is passthrough, 1 is ok to arm, 2 is arming is prevented, 4 is armed
- Tmp2 (only of there is GPS sensor available) : GPS lock status, Number is sent as 1234, the numbers are aditives : 1 is GPS Fix, 2 is GPS Home fix, not used, not used, number of sats
- VFAS : actual vbat value.
- GAlt : GPS altitude, sea level is zero.
- GSpd : current speed, calculated by GPS.
- GPS : GPS coordinates.
Cels : average cell value, vbat divided by cell number. Didn’t find this. Seems to be Vfas or A4.
- RxBAT : voltage of F3E
- Curr : current from main battery if sensor is used, unit in mA
- Fuel : something is provided but cannot figure out that yet — should be consumed battery depending on the current sensor (it should be set to mAh in the radio)
My setup and board test:
- KDS Kylin 210 frame
- KDS Kylin 2204/2300kv motors
- SoloGood 20A DShot300 ESCs
- FrSKY XSRF3O
- Matek PDB
- Foxeer 700TVL CMOS FPV cam
- KDS Kylin 5,8Ghz 600mW VTX
- Aomway 5.8Ghz cloverleaf antenna
- Some addressable LED strip
- KingKong 504530 blade props
- 1,300mAh Bonka 45-90C 4S
As usually, I’ve taken KDS Kylin 210 racing frame with some new SoloGood ESCs (read my review here) + Kylin 2204|2300kv motors and swapped SpRacing F3 board with XSRF3O. I use DShot300 digital protocol between ESCs and board (read what is DShot and how to deal with it here), 4|4KHz PID and gyro loop rates, OSD and telemetry.
Everyhing flies perfect. 100% as expected and no flaws what-so-ever. Flight is very precise and totally under control. I would say that PID should even be brought down a little bit to get rid of so precise feel on the sticks… 🙂 Concerning that PID tuning is very easy for this board — it can be set in wide variety of values. And we didn’t use much dampening under the board — only usual silicone rings between plastic board standoffs and board itself. Our current configuration has the same feel as if we are using some more capable F3Evo boards. This effect is due to the DShot300 used on ESCs and tuned PIDs (although I would have to tune it a bit more to get better stops after stick inputs). So, if I would fly F3Evo and F3 with the same setup, one after another, not knowing which is which — I don’t think that I’d be able to guess the board right… It is a matter how well F3 board is cooked.
Comparing to my previous F3 board — now I have OSD, less weight because of the intergrated receiver, less cables and SDcard slot for blackbox feature. Definitely and upgrade from SpRacing F3!!!
XSRF3O initial test flight: