Review: Betaflight F4 Flight Controller

Anyone who uses Betaflight should be familiar with the Betaflight F3 flight controller. FPVModel has just upgraded it and put a F4 processor in it. In this review we will also check out other changes.

The Betaflight F4 flight controller is now available at FPVModel. To learn more about flight controllers, here is our guide.

Unboxing and Features

The Betaflight F4 FC comes in a plastic box, with only the board itself, and a 10cm servo cable. It would be nice to see some low ESR capacitors or even soft-mount rubber bobbins included.

  • F4, MPU6000
  • Integrated PDB
  • Betaflight OSD
  • Current Sensor (up to 145A)
  • Flash Memory for Blackbox
  • 5V / 1.5A BEC

Betaflight F4 VS F3

Let’s compare the new and old Betaflight boards, here is our review of the Betaflight F3 FC.

Similarities

The board layout and dimension are nearly identical: the motor output pins, UART’s, camera in/out etc…

Differences

The biggest change seems to be the processor. They’ve also used a lower rating but reportedly more reliable 5V BEC. It comes with BLHeli32 ESC Telemetry pads (RX1 between motor output and GND). Finally they replaced the SD card slot for Blackbox with a flash memory chip.

However just like many other F4 flight controller, you have to perform the uninverted Smart Port hack to get SPort Telemetry to work. It’s not a hard thing to do, and the latest R-XSR receiver even has a breakout pad for easy soldering.

Here is a table to summarize the changes:

Betaflight F4 Betaflight F3
Processor STM32 F405 STM32 F303
IMU (Gyro) MPU6000 MPU6000
BEC [email protected] [email protected]
ESC Telemetry Pad Yes No
Blackbox Medium Flash Memory Micro SD Card
Price $45 $43

Why Betaflight F4?

F4 is a more powerful processor than the F3 (for detail differences between different STM32 processors, check out this post).

But is it worth the upgrade for existing Betaflight F3 users? I would say it depends heavily on how much you care about running the fastest looptime and the latest BF features. For new buyers, it’s a no brainier to get the latest F4 boards.

Since the release of Betaflight V3.2, we started to see many F3 FC users complaining about high CPU usage. This is mainly caused by the new Dynamic Filter feature, which is too much for F3 processors. F3 users have been asked to lower their looptime from 8K to 4K when running Dynamic Filter.

Therefore if you want to run the fastest possible looptime (i.e. 8K/8K) with Dynamic Filter on, more powerful processors like the F4 is the way to go.

Notes about Smart Port and SmartAudio

FPVModel suggests using Soft Serial for Smart Port Telemetry and SmartAudio, but I found that it’s not necessary to use Soft Serial, both can be setup on normal UART’s just fine.

However, I was having problem setting SmartAudio on UART1’s TX, I even try setting UART1’s TX pin as soft serial still no joy.

UART2 just doesn’t seem to work for either Smart Audio or Smart Port at all, with or without Soft Serial. Just very odd issues I have no clue why.

In the end I had to put Smart Port to UART1’s TX, and use UART3’s TX for SmartAudio. This is the only combination that works for me.

Update about UART (16 Nov 2017)

So I couldn’t get UART2 to work at all for Smart Audio and Smart Port, and it turns out UART2  has inverter on both TX and RX.

You can use UART2 for SmartPort with some modification: you will need to get a small signal schottky diode connecting TX to RX, and connect Smart Port to the RX. And turn off tlm_halfduplex in CLI

I have also successfully setup Smart Audio and Smart Port using soft serial on both UART1 and UART3. Make sure you power cycle the flight controller and TX, it didn’t work before probably because I didn’t do that.

10 thoughts on “Review: Betaflight F4 Flight Controller

  1. JamboFPV

    I am getting pretty bad video with a lot of noise, I am using Foxeer Arrow V3 and a Tramp HV. I have tried wiring Cam to 5v which seemed to not provide enough power and now am powering direct from the batt +. I am also using a capacitor across the batter connectors. I am thinking of just running to run video directly from VTX to cam.. which kind of sucks because one of the reasons I wanted to try Betaflight is OSD. Any Ideas?

    Reply
  2. Totostao

    I’m using a unified TBS unify RACE, and the new FC BetaflightF4 and when I connect everything as indicated in the diagram I have the problem of not being able to see the osd, but when I disconnect the camera the osd works perfectly. How can I fix it?

    Reply
      1. Charlie

        second relpy, after a little more research. I didn’t have my camera set to the correct format, I think it was on ntsc and needed to be on pal

    1. Charlie

      I’m having the same problem, right down to disconnecting the camera and osd shows up :) I hope we can figure it out

      Reply
  3. Brian Wright

    I just got mine wired up but haven’t flown it other than hovering in the basement yet. The dataflash chip on mine appears to be bad. I double checked and I didn’t knick or short anything while soldering. The configurator couldn’t put the board into DFU; I had to use the boot button. I flashed 3.2.1. Configurator still can’t put the board into DFU. I’m curious to see if anyone else had that issue or if I got an unlucky manufacturer defect. Soldering was relatively easy, but the grounds for the ESCs do seem to soak up heat. I’ll report back if anything significant comes up while flying next week.

    Reply
    1. BigMushyPurples

      I’ve had a number of FC’s boot button go bad on me and was preventing me from flashing via DFU. I was able to bridge the two boot pads with tweezers bypassing the button all-together. Doubt this would be an issue with a brand new board, but just sharing my experience with previous BF F3 boards.

      Reply
    2. Brian

      It’s been a week. No problems to report. My data flash chip started working randomly a couple of days ago after a decent crash. I suspect the factory soldering is faulty and the crash restored connectivity. Everything else seems to be performing well. I’m running 8k/8k and it’s not pushing the CPU at all. So far I’m pretty happy with the purchase. I wish it had a dedicated FPV camera control pin so I didn’t have to choose between LEDs and that.

      Reply
    3. Brian Wright

      The dataflash chip isn’t working again. I started get noise on the analog ground in my fpv feed. I swapped the ground on the 5v row below it and that fixed the issue. Still working very well. I was able to turn off all my static filters today and the quad flies amazingly. I think I like this board much better than the DYS F4 Pro I was using before. If the dataflash worked it would be perfect. I haven’t tuned this quad and I’m still using stock PIDs but when it comes time to tune I’m sure I’ll wish I had the blackbox.

      Reply
  4. Matt

    All of my BF F3 boards started having critical failures at the same time, possibly due to CPU usage and possibly due to BEC failures. I have since upgraded all my rigs to BF F4, initially there were some really awful mid throttle oscillations, really really terrible. I did the PT1 Lowpass Filter and incrementally eliminated notch filters checking motors each time (I was worried the oscillations were bad noise). These changes made all the difference, went to butter smooth flight and motors come down cool to slightly warm. Utilizing Quadrant_32 ESC’s or any other 4in1 ESC is non trivial if you want to use the on board current sensor, also the motor pins make for a less than clean build for a 4in1. My next build will probably use the Betaflight ESC’s to check out that goodness. All in all I really like the FC though I will need to put it through its paces before I could decide if its long term tough.

    Reply

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