Following our review of the XSRF3O flight controller with integrated Frsky XSR RX, FrSky provided us with the other 3 flight controllers of the same FC line up to check out: the XSRF4O, XSRF3PO and XSRF4PO.
Check out this post to learn more about How to choose flight controller. This review is written by Artur Banach. Check out our review of the XSRF3O.
These flight controllers are available from the following vendors:
- XSRF3O (HorusRC | Banggood)
- XSRF3PO (HorusRC | Banggood)
- XSRF4O (HorusRC | Banggood)
- XSRF4PO (HorusRC | Banggood)
A feature comparison table between these Frsky FC’s.
| XSRF3O | XSRF3PO | XSRF4O | XSRF4PO | |
| Processor | F3 | F3 | F4 | F4 |
| IMU (Gyro) | MPU6050-I2C | MPU6050-I2C | MPU6000-SPI | MPU6000-SPI |
| PDB Integrated? | No | Yes | No | Yes |
| MicroSD for Blackbox? | Yes | Yes | Yes | Yes |
| Number of PWM outputs | 8 | 8 | 6 | 6 |
| Operating Voltage | 4V-10V | up to 6S | 4V-10V | up to 6S |
| Betaflight OSD | Yes | Yes | Yes | Yes |
| Dimension | 36mm x 36mm | 60mm x 36mm | 36mm x 36mm | 60mm x 36mm |
| Weight | 6g | 14g | 6g | 14g |
| Price | $40 | $50 | $50 | $60 |
XSRF3PO
The XSRF3PO flight controller is basically the XSRF3O but with PDB integrated.
Inside the XSRF3PO box:
- XSRF3O Flight Controller
- Set of pins for soldering
- Instruction manual
Table of Contents
Specs
- STM32F303 – F3 Processor
- MPU6050 Gyro
- Built in Power Distribution Board up to 6S
- Built in current sensor
- Built in Betaflight OSD (compatible with Betaflight configurator)
- Integrated full range XSR radio receiver with Smart Port telemetry
- Built in Micro SD card slot for BlackBox
- 60mm x 36m with 30.5mm mounting holes
- 12.8g in weight
The choice of MPU6050 Gyro is a poor decision in our opinion, because it’s limited to I2C BUS (no SPI) and therefore it can only run a maximum gyro sampling rate of 4KHz.
The board is in rectangular shape due to the amount of components soldered on it. Solder pads for ESC power and signals are in the four corners corresponding to the Betaflight motor order. Solder pads for video section are located at the front, next to the smart port connector (for flashing the built in receiver) and buzzer port.
MicroSD card slot is facing outwards for easy card removal. XSR built in receiver antennas are fitted to the board with W.FL connectors, so they can be easy replaced if needed. Antennas are directed outwards by default. Exposed antenna element is just under 33mm long and both antennas have a total length of 145mm.
Betaflight Settings
The board comes flashed with Betaflight 3.2 (FRSKYF3 Target) and the ports are all pre-configured specifically for SmartPort and receiver and it works out of the box.
XSRF3PO has the same gyro as the XSRF3O and can only do 4K/4K gyro refresh rate and loop time without maxing out CPU load.
Great things about XSRF3PO
- Integrated RX for cleaner builds and better convenience
- Good value for money considering it’s basically 3 components in 1 board: FC, PDB and RX
- MicroSD card logger available for Blackbox
- Good pads layout
- Supports up to 8 PWM inputs and supports hex and octo configuration
- Betaflight is already configured and ready to use
Things to be aware of
- Bad choice of Gyro
- Unusual shape might not be possible to use with very tight racing frames
- With default orientation antennas are sticking side way
XSRF4PO
XSRF4PO is very similar to the XSRF3PO above, with the main difference of F4 processor and MPU6000 SPI gyro.
Specs
- STMF32F405 – F4 Processor
- MPU6000 SPI Gyro
- Built in Power Distribution Board up to 6S
- Built in current sensor
- Built in Betaflight OSD (compatible with Betaflight configurator)
- Integrated full range XSR radio receiver with Smart Port telemetry
- Built in Micro SD card slot for BlackBox
- 60mm x 36m with 30.5mm mounting holes
- 13.6g in weight
XSRF4PO shares the same shape and dimensions as the Frsky F3 PDB board. It can support hexacopter configuration by having 6 PWM outputs. Solder pad arrangement is similar to F3 version.
The board comes flashed with Betaflight 3.2 (with target OMNIBUSF4 for some reason).
Gyro refresh rate and loop time can be set to 8K/8K safely thanks to the MPU6000 gyro and F4 processor.
One common problem with F4 boards is the lack of UART inverters, where you either need built-in inverters or getting the uninverted signal to use SBUS or SmartPort. With the XSRF4PO this isn’t a problem any longer as both SPort and SBUS are working right out of the box.
The rest of the features are identical to the XSRF3PO.
Great things about XSRF4PO
- Integrated RX for cleaner builds and better convenience
- Very good value for the price considering it’s basically 3 components in 1 board
- MicroSD card logger for Blackbox
- Good pads layout
- SmartPort and SBUS pre-configured
- Good gyro choice and plenty of CPU power with the F4 processor
Things to be aware of
- Unusual shape might not be possible to use with very tight racing frames
- With default orientation antennas are sticking out sideway
XSRF4O
Last but not least is the XSRF4O board that shares a lot of common features with XSRF3O. It’s basically the XSRF4PO above without the PDB capability.
Inside the box, it comes with:
- XSRF3O Flight Controller
- Set of pins for soldering
- Instruction manual
Specs
- STM32F405 CPU – F4 Processor
- MPU6000 SPI Gyro
- Built in Betaflight OSD
- Integrated full range XSR radio receiver with Smart Port telemetry
- Built in Micro SD card slot for BlackBox
- Operating Voltage Range: 4-10V (it can’t be powered directly from LiPo battery)
- 36x36mm with 30.5mm mounting holes
- 7g in weight
The board we have received, unlike other ones, came pre-flashed with Betaflight 3.1.7 (with target OMNIBUSF4) and the receiver and port weren’t setup properly.
Gyro refresh rate and loop time can be set to 8K/8K with the MPU6000 SPI gyro and F4 processor.
Again, despite being an F4 board, you don’t need to worry about UART inverters for SmartPort and SBUS as they work out of the box.
Great things about XSRF4O
- Integrated RX for cleaner builds and better convenience
- MicroSD card logger – useful for tuning with Blackbox
- Good pads layout
- Supports up to 6 PWM inputs (as opposed to 8 on F3 version)
- Good gyro choice and plenty of CPU power with F4 processor
Things to be aware of
- MicroSD card slot orientation on the board is facing inwards making it more difficult to access inside the frame
- Additional 5V voltage regulator or PDB is required to power this FC
Conclusion
FrSky’s new flight controller line-up is quite interesting because for the first time we have XSR radio receiver incorporated into the main board. It saves hassle of having a separate component to wire up and leaves more space for the build. Each of the boards have different features and prices making it very flexible for different situations.
21 comments
Does the XSRF4PO provide enougth Current on its 5V rail to power other components on a quad? Like VTX or CAM?
Did someone was able to update the receiver port of the XSRF4PO. I hook it up to Taranis, but only get an “external module communications” error.
Had no problems when flashing XSR.
I would like to try the Fport on it to free the third (6’th) uart for split control (using UART3 for smartaudio LUA)
Hi Oscar
Can you help?
Loving the XSRF40 it makes a neat build.
But I can’t get RSSI working on the osd?
I’ve got it on channel 8 on Betaflight but it doesn’t move on the tab?
or the osd?
Can you help? and thanks for any help!
cheers Jamie
On the bench or at all?
I through I had the same problem. It turns out that that scaling is different then on the radio and it does not move when close on the bench.
Try moving away/ covering the antena/ testing in range mode.
I have to get use to the reading but it works for me… kind of.
I had the same problem, where everything was working fine just no rssi reading on osd. Did a firmware update with the latest frsky f4 build to get uart 3 set up with runcam control (which didnt work until the latest update that came out a couple days ago) Now i have rssi but no vfas or current reading.
Hi Oscar,
just little clarification on your “pro & con” on the XSRF4O:
XSRF4O to get “Vfas” sensor (main batt voltage) and current – assume it can be done as on XSR F3O:
marketchangers.files.wordpress.com/2017/03/xsrf3e_my_scheme1.jpg?w=930
i. e. welding cable connection from ESC/PDB batt in pads (+/-) to FC`s “vbat +” and “GND -” pads.
BUT – the con is that to get CURRENT sensing, it requires an additional, external 3,3 V sensor (as far as I understand).
To make it more clear:
Difference between
XSRF4O – having 280 Baro – but NO INTEGRATE current sensor (so you will need a seperate piece ….disatvantage)
XSRF4PO – having PDB including integrated current sensor – but having NO BARO ….why, Mr. Frysky…? O.k. you could hook up a tiny 280 to it – but i do not know how, since never done that.
Hi! Do you know how to utilize PWM5 & PWM6 pins on XSRF4O?
I want to map AUX channels to control servo and video-switcher board, but cant figure out how to do it.
I solved problem myself – to be used as servo channels PWM5/6 pins should be configured with “resource” CLI command. Initially they are bound to “motor 5” and “motor 6” functions, so you need to free them (by mapping to NONE) and then map to SERVO 1 & 2 (or whatever you like). Details could be found here: https://github.com/betaflight/betaflight/wiki/Betaflight-resource-remapping
Is it possible to add GPS to these? If so, what are the options? There doesn’t seem to be any general purpose I/O pins for this.
Thanks,
These FC have limited number of UART’s, and they are really designed for racing and mini quad’s. You should be looking at iNav if you plan to use GPS, they actually have a list of suggested FC you can use.
Hi, on RCGROUPS somebody has add GPS on the XSRF3O for inav support.
It is worth mentioning that the XSRF40 (and possibly the other F4 boards) do not have an exposed UART available. For folks who want to use things like TBS Smartaudio you can’t. No place to solder the wire! I had ordered XSRF40 for a new build and had to send it back. I confirmed the lack of a connection point with FrSky support. Very disappointing.
I checked with FrSky as well. XSRF4O doesn’t have that but rest of the board do. I was told that XSRF4O will be revised to address this issue.
You can do softserial on led strip
Hi, thanks for that hint.
Do you know of any resources where enabeling TBS SmartAudio via softserial on the led strip is explained?
I viewed a lot of videos now, unfortunately without an exact hnit how to achieve it but finally managed it by searching the betaflight docs and reading github.com/betaflight/betaflight/wiki/Single-Wire-Software-Serial
Now I had an idea how it should work and this is how it’s done:
Just for the search engines: How to enable Smart Audio with Software Serial (softserial) on the led strip pin on FrSky XSRF4O
* Solder the SmartAudio cable from the VTX to the LED signal solderpadd on the FC
* Connect the FC to the BF GUI
* Dump your BF cli and save it on your harddisk (but you shouldn’t need it)
* Enable the SOFTSERIAL feature on the Configuration tab
* Save and reboot into the GUI again
* Go to the CLI tab
* Enter the following into the CLI:
resource
# …will tell you:
# …
# resource LED_STRIP 1 B06
# …
# Free pin B06 from LED_STRIP 1:
resource LED_STRIP 1 NONE
# Assign pin B06 to the softserial serial_tx 11
resource serial_tx 11 B06
# …and save
save
* Open the Ports tab in the BF GUI: Now you should see the additional identifier SOFTSERIAL1
* In the column Peripherals enable TBS SmartAudio with speed on Auto
* Save and Reboot
Now check your configuration in your goggles
You’ll find the VTX config options under: FEATURES -> VTX SA
Hi Oscar…thanks for summing these up. Im not a huge fan of AIO but if you team up the XSRF4PO with the Matek VTX-HV you would get a very lightweight and streamlined build I expect…shame about the antenna sticking out the side! Steve
thanks Steve, that’s an interesting idea!
I see its only XSRF4O which have built in barometer, which is a winner if you intend to use it with example INAV.
XSRF4O having baro (think its Bosch 280) – and XSRF4PO having NO baro