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What is the difference between the STM32F411 and the STM32F722RET6 processors in flight controllers? What are the advantages of having the F7 processor over the F4 processor?

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    $\begingroup$ F4 and F7 are two different series of microprocessors from STM. In order to make fair comparisons between the two, we'd need to know what two F4 and F7 parts you're asking about. $\endgroup$
    – ifconfig
    Apr 19, 2020 at 6:12
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    $\begingroup$ STM32F411 and STM32F722RET6. $\endgroup$
    – Jacob B
    Apr 19, 2020 at 6:59
  • $\begingroup$ @ifconfig I think that's actually too much information. The F4 and F7 lines have some fundamental differences which are driven by ARM Cortex characteristics. Those are more important than the RAM or processor speed. $\endgroup$ Apr 19, 2020 at 12:29
  • $\begingroup$ Also the STM32F405 is much more common in flight controllers. The F411 is typically used in small footprint flight controllers only. $\endgroup$
    – QuadMcFly
    Apr 20, 2020 at 13:29

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There are a few differences:

Firstly, the F7 chip used in F7 flight controllers operates at a much higher frequency, so can handle more operations per second.

This is useful when you want to start adding lots of dynamic filters, for example RPM filtering, alongside features such as antigravity.

Whilst an F4 can handle almost anything you will want to throw at it in this respect, it will not be able to do so forever (the F3 used to be standard but is now lacking features). Therefore, F7 is better for future proofing.

F7 flight controllers also have extra UARTs. This can be very useful if you want lots of extra features, for example SmartPort telemetry, Smart Audio, GPS and camera control. However, it is not the end of the world if you don’t have as many UARTs as you want as you can use softserial to add software UARTs to your FC. Of course, this also takes up processing power so an F7 may cope better.

Finally, F7 flight controllers have built in inverters on their UART ports, while F4's do not. So an F7 FC can handle any inverted signal "as is" on any of its numerous UARTs, while F4 flight controllers have a dedicated external inverter chip on the PCB connected to one of the UARTs.

Because of that, F7's make it easier to use UARTs for SBUS or other inverted signals as it means you can hook them up anywhere without any inversion mods, while on an F4 controller you can only use the special inverted pads (of which there is usually only one, labeled "SBUS").

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The short answer is that F7 is faster than F4, mainly because the F7 can execute two instructions simultaneously. At 216 MHz clockspeed, the STM32F722RE series you asked about has more than double the frequency of the STM32F411 series.

What might matter the most apart from the speed when it comes to flight controllers is UARTs; the STM32F411 has 3 of them, and they can't handle inverted signals. The STM32F722RE has 4, that can handle inverted signals

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If you are asking "real world" differences on how it flies, how it feels and reacts, the short answer is none. There are no differences for typical fpv quadcopters in how they fly and react.

If you add lots of sensors or non typical setups (8 motors, wooden frame with monster vibrations,custom coded firmware) , there will be differences but for say your 2-3-4-5-6 inch FPV quadcopter without GPS or sensors running in ACRO 100% of the time, controlled by ELRS/CRSF there are no differences at all, both F4 and F7 can run equally well Beta Flight.

Maybe in future there will be the need for a more powerful processor, but 3 years are already passed from the original question and all my F411 and F405 and F722 fly exactly the same on the latest BF 4.4.

Personally i would go for F405 for long range drones (LIDAR, GPS) and INAV planes (lots of sensors) leaving F411 for AIO builds. F722 only if it is a really good deal (price difference 10$). Also mind that F405 and F722 have more UARTS and to use them fully avoid AIO boards that do not implement all the required pads properly. A full FC/ESC stack has more and larger pads to solder and to use the full set of ports.

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The shortest answer would be F4 is the Psx4, and F7 is the Psx5 :) The cpu load that you see being handled in betaflight will be handled with more or less ease, depending in the strnegth of the "cpu"...that brings the question of longevity into play also...

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