Custom FC using NucleoH7A3ZI-Q: Building a DIY Flight Controller

What’s holding back your drone project? If you’ve ever tried building a custom FC (flight controller) using the NucleoH7A3ZI-Q board, you’ve probably noticed it’s not exactly plug-and-play. Most open-source drone firmware skips support for this STM32H7 dev board—leaving many tinkerers scratching their heads. But don’t give up yet! Here’s how to work around the main hurdles, from firmware compatibility to that frustrating USB connection problem.

Why Choose the NucleoH7A3ZI-Q for a Custom FC?

The Nucleo-H7A3ZI-Q is a powerful dev board based on the STM32H7 series microcontroller. It offers impressive processing speed and plenty of IO options—perfect for someone looking to build a custom FC with room to experiment.

Pairing this board with sensors like the ICM-20948 IMU and DPS310 barometric sensor gives you a solid hardware base. However, the main challenge is software support—mainstream flight firmware like PX4 and ArduPilot don’t natively support this specific Nucleo board out of the box.

Getting Your NucleoH7A3ZI-Q Running as a Flight Controller

This is where things get tricky. While PX4 and ArduPilot offer broad support for STM32 microcontrollers, they’re usually tailored to specific boards. The NucleoH7A3ZI-Q isn’t officially on their compatibility lists. So what can you do?

• Port existing firmware: Both PX4 and ArduPilot are open source—so with some effort, you can adapt their code to work with your board. This means editing configuration files, pin mappings, and sometimes writing board-specific drivers.
• Start simple: Before diving into porting full-featured firmware, try flashing a basic RTOS or even bare-metal code that reads data from your ICM-20948 and DPS310. Once you confirm hardware communication, you’ll have a much easier time troubleshooting bigger firmware stacks.
• Leverage STM32CubeIDE: STMicroelectronics’ own tools make initializing peripherals and generating startup code easier. Check out the STM32CubeIDE if you haven’t already—it’s perfect for SPI/I2C sensor setup and early prototyping.
• Use community forums: Sites like ArduPilot Discuss or the PX4 forums are full of folks who’ve faced similar challenges. A quick search can save hours of frustration.

Troubleshooting USB COM Port Issues on NucleoH7A3ZI-Q

Not seeing that COM port when plugging into the user USB? This is a classic stumbling block. The Nucleo boards come with two USB ports: one connected to the ST-Link debugger (which shows up as a COM port easily), and the other wired directly to the MCU (“user” USB).

Here’s what’s happening: unless your firmware specifically initializes the MCU’s USB peripheral as a virtual COM port (using something like CDC-ACM class), Windows or Mac won’t recognize it as a serial device.

To get your NucleoH7A3ZI-Q’s user USB working as a COM port:

• Add USB support in firmware: Use STM32CubeMX (built into CubeIDE) to enable CDC-ACM support in your project. This tells the microcontroller to behave like a serial device.
• Check device drivers: Sometimes Windows needs drivers for STM32 virtual COM ports. ST provides official drivers on their USB driver page.
• Verify USB cable: Not all micro-USB cables are created equal! Double-check with a known good data cable—charge-only cables won’t cut it.
• Tweak device settings: If using bare-metal code, make sure endpoints and descriptors are configured properly for CDC operation.

Once this is set up, your user USB should show up as a new COM port in device manager. From there, tools like Mission Planner will be able to connect.

An Anecdote: Lessons Learned Building a Custom FC

A friend once spent days puzzled by why their custom FC wouldn’t show up in Mission Planner over USB, only to realize they’d never enabled the CDC-ACM middleware in CubeMX. After adding that one checkmark and regenerating code, everything snapped into place. Sometimes it’s not about reinventing the wheel—it’s about double-checking each step.

Your Next Steps: Expanding Custom FC Capabilities

Once your basic setup works, there’s plenty of room to grow:

• Add GPS modules for advanced navigation.
• Connect telemetry radios for real-time flight data.
• Tune PID controllers using test flights and log analysis.
• Dive deeper into sensor fusion algorithms for better stability.

Building a custom FC using NucleoH7A3ZI-Q takes patience but offers huge learning potential. If you’ve solved a tricky issue or found a cool workaround, what’s your best advice for others starting their own custom flight controller journey?