"Onboard processing" is used loosely in FPV marketing. In practice a flight controller does not run neural networks. What it does run is a stabilisation loop, a set of sensor drivers, an OSD and a blackbox logger, all inside a hard real-time budget measured in microseconds. Choosing a board is therefore a question of how much sensor and logging work you are asking it to do at the same time, not of how modern the model name sounds.
This guide sets out what each MCU tier can carry, why the sensor package usually matters more than the processor badge, and when an AIO board is the right answer instead of a separate stack.
What actually runs on the flight controller
Four workloads compete for the same core:
•The rate loop. Gyro sampling and PID output, typically at 4–8 kHz. This has hard deadlines and cannot be delayed.
•Sensor drivers. Barometer, magnetometer, GNSS, optical flow and rangefinders all poll the same bus. Each additional device adds jitter to the loop.
•OSD and telemetry. Cheap in cycles but sensitive to timing, because the OSD chip is shared with the video path.
•Logging. The quiet cost. High-rate blackbox logging writes to flash or SD continuously, and it is the workload that most often forces an upgrade.
Higher-level autonomy — object detection, visual navigation, path planning — is normally offloaded to a companion computer that sends commands to the flight controller over a serial or CAN link. The flight controller executes; it does not infer. That distinction decides which board you actually need.
The three MCU tiers
| Board | MCU | Memory | Practical ceiling |
| F405 Flight Controller | STM32F405, Cortex-M4 @ 168 MHz | 192 KB SRAM / 1 MB flash | Clean 5-inch freestyle, basic GPS rescue, moderate logging |
| F722 Flight Controller | STM32F722, Cortex-M7 @ 216 MHz | 256 KB SRAM / 512 KB flash | Higher loop rates, 4 kHz logging, more serial devices |
| H743 Flight Controller | STM32H743, Cortex-M7 @ 480 MHz, dual FPU | 1 MB SRAM / 2 MB flash | Dual IMU, full sensor fusion, high-rate logging, ArduPilot-class firmware |
The F405 is not obsolete. It is a 168 MHz M4 with 192 KB of RAM, and for a 5-inch freestyle quad running a modern firmware build it is entirely sufficient. Its limit appears when you add devices: 6 UARTs, 8 PWM outputs and 16 MB of blackbox flash is a comfortable budget until you want GNSS, optical flow, a rangefinder and high-rate logging on the same board.
The F722 moves to a Cortex-M7 at 216 MHz with 256 KB of SRAM and an ICM42688-P gyro sampling at 32 kHz. That extra headroom is what allows 4 kHz blackbox logging without dropping loop time. It is the sensible middle tier for builds that are not freestyle-only.
The H743 doubles the clock again and quadruples SRAM to 1 MB, which is what makes a dual IMU arrangement practical: the H743 board carries a BMI270 for the 32 kHz gyro path plus a BMI088, along with an IST8310 magnetometer and a DPS310 barometer, 7 UARTs, 10 PWM outputs, a CAN bus and a TF-card blackbox. That combination — two IMUs plus a full sensor suite plus a CAN bus — is the actual reason to buy it. The MHz number on its own is not.
The sensor package is the real differentiator
Two boards can share a processor and behave completely differently because of what is soldered next to it. Compare the barometers: the F405 and F722 boards use a BMP280 rated to about ±0.12 hPa, while the H743 uses a DPS310 specified at ±0.005 hPa in high-precision mode. That is an altitude resolution difference of roughly an order of magnitude, and it shows up directly in altitude-hold behaviour.
The magnetometer tells the same story. A dedicated IST8310 on the H743 gives a usable heading reference for navigation modes without relying on the GNSS course over ground, which is unreliable at low speed. On the F405 and F722, heading normally comes from the GNSS module or not at all.
If your build only needs rate-mode acro and an OSD, this section does not apply to you. If it needs position hold, return-to-home or autonomous waypoints, the sensor package is the deciding factor, not the MCU.
AIO versus separate stack
An all-in-one board fuses flight controller and 4-in-1 ESC onto one PCB. The AIO H743 with 45A ESC carries an STM32H743VIT6, a BMI270 primary IMU with an ICM-42688-P backup, 16 MB of QSPI flash at 8 kHz logging, dual camera inputs with OSD switching, and runs 2–6S. It is 36×36×10 mm, which is how a whole flight stack fits inside a ducted 3-inch frame.
A separate H743 standard stack with an 85A ESC trades that compactness for serviceability and current headroom: 2–8S input, 5V@4A plus 9V@3A plus VBAT outputs, 8 UARTs, CAN, and a 38×38 mm board. When one half fails you replace one half.
•Choose AIO when volume and mass dominate — sub-250 g builds, ducted frames, tight 20×20 stacks.
•Choose a stack when current per motor is high, when you expect to replace ESCs after crashes, or when the airframe has room for 30.5×30.5 mounting.
Match the rail and the mounting before anything else
Two specifications cause most returns and most dead-on-arrival reports, and neither is the processor:
•Input voltage. The F405 is rated 2–8S (7.4–25.2 V), the F722 2–8S (11.1–33.6 V), the H743 2–8S (12.6–33.6 V), and the AIO 2–6S (7.4–25.2 V). A 6S AIO on an 8S build is a failure waiting for the first throttle punch.
•Mounting pattern. 30.5×30.5 mm and 20×20 mm are not interchangeable without an adapter, and stack height has to clear the frame's standoffs — 15–20 mm on a 3-inch frame, 28–35 mm on a 5-inch, 35–50 mm on a 13-inch.
Where the propulsion controller fits
On high-power builds the flight controller and the motor controller are separate systems that talk over a bus. The H743 and the standard stack both expose a CAN interface, which is the link a VESC-class propulsion controller uses to publish telemetry and accept commands. Our VESC motor controllers cover 100 A to 3000 A for airframes where a 4-in-1 ESC is not enough current.
FAQ
Can the flight controller run computer vision? Not in any practical sense. Vision workloads run on a companion computer, which sends position or velocity commands to the flight controller. Buy the flight controller for loop stability, I/O and logging, and budget the companion computer separately.
Do I need dual gyros? Only if you fly ArduPilot-class firmware that uses a second IMU for redundancy, or if you want vibration-tolerant filtering across two different sensor types. For Betaflight freestyle, a single ICM42688-P is fine.
Is 1 MB of SRAM worth the price difference? It is when you enable high-rate logging with several sensors attached. If you log at low rate and fly rate mode, the F405's 192 KB will not be your bottleneck.
Does a higher clock rate improve flight feel? Indirectly, by allowing a higher and more consistent loop rate. Feel is dominated by tuning, gyro quality and frame stiffness.
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