Pi 4 Boot Failure: Duet 2 & Fysetc H36 Troubleshooting

Hey guys! Ever run into a frustrating tech issue that just makes you wanna pull your hair out? Well, I recently battled a super annoying problem with my Raspberry Pi 4B, and I figured I'd share my troubleshooting journey and the eventual fix. This guide is all about tackling a boot failure when you've got a Duet 2 and a Fysetc H36 board hooked up to your Pi. Trust me, it's a head-scratcher, but we'll get through it together!

Understanding the Setup

Before we dive into the nitty-gritty, let's break down my setup. This is crucial because the specifics of your hardware and power configuration can play a huge role in diagnosing the problem. So, let’s get started, understanding your setup is the first step in resolving this issue.

My Hardware and Power Configuration

• Pi Model: I'm rocking a Raspberry Pi 4 Model B with 2GB of RAM. This is a pretty common setup, but it's always good to double-check which model you're working with. Different models can sometimes have quirks.
• Power: Power is super important! I'm using a dedicated 5V 3A PSU (Power Supply Unit) connected directly to the GPIO (General Purpose Input/Output) 5V and GND (Ground) pins. This ensures the Pi gets a stable and sufficient power supply. Trust me, a weak power supply can cause all sorts of weird issues.
• USB Device 1: My primary controller is a Duet 2, running Klipper firmware. Klipper is awesome, but sometimes it can be a bit finicky with hardware compatibility.
• USB Device 2: I also have a Fysetc H36 Combo Board connected, also running Klipper firmware. This board adds some extra functionality to my setup, but it's also a potential source of conflict.

Both the Duet 2 and the Fysetc H36 boards have their own separate 24V PSUs. This is important because it means they aren't drawing power from the Pi itself. However, to ensure proper communication and prevent ground loops, both the 24V PSUs and the Pi's 5V PSU share a common ground. The USB connections are purely for data transfer between the boards and the Pi. This is a key detail because it means the issue isn't likely related to power being drawn through the USB ports.

The Problem: Boot Failure

Okay, so here's the main headache: My Raspberry Pi 4 just refuses to boot up properly when both the Duet 2 and Fysetc H36 boards are connected to the USB ports. It's like the Pi gets stuck in some kind of pre-boot limbo. This happens whether I'm doing a cold start (powering on from completely off) or a reboot (restarting the system). There are absolutely no signs of life – no blinking LEDs, no HDMI signal, nada. It’s a ghost town!

But here's the really weird part: If I disconnect either the Duet 2 or the Fysetc H36 before booting, the Pi fires up perfectly. I can even plug the disconnected device back in immediately after the boot process starts, and everything works flawlessly. Both devices are recognized, and they function exactly as they should within the operating system. This strongly suggests that the issue is something that happens specifically during the boot process, not a general incompatibility. The Raspberry Pi 4 boot failure is only occurring when both the Duet 2 and Fysetc H36 boards are connected.

Troubleshooting Steps: My Detective Work

So, naturally, I put on my detective hat and started digging. Here are the steps I took to try and figure out what was going on. Troubleshooting is crucial to identify raspberry pi 4 boot failure causes.

1. Verifying the EEPROM Firmware

First things first, I wanted to make sure my bootloader was up to date. The bootloader is the Pi's firmware that handles the initial startup process, and outdated firmware can sometimes cause compatibility issues. The latest EEPROM firmware verification is important.

I used the rpi-eeprom-update tool to check the firmware version, and it turned out I was already running the latest version available (dated May 8 2025). So, that ruled out an outdated bootloader as the culprit. Keeping your firmware updated is always a good practice, but in this case, it wasn't the magic bullet. However, it's always a good idea to start with the basics. Making sure your firmware is up-to-date is like making sure you have the latest version of an app on your phone – it often fixes bugs and improves performance.

2. USB Port Isolation Testing

Next, I started thinking about the USB ports themselves. Maybe there was some kind of conflict or limitation with how the Pi was handling multiple USB devices during boot. So, I decided to try different USB port configurations. This involves USB port isolation testing to identify if specific ports are causing the issue.

The Raspberry Pi 4 has both USB 2.0 and USB 3.0 ports, and internally, they're connected to different USB controllers. My thinking was that maybe the problem was related to both devices being on the same controller. So, I tried connecting the Duet 2 to a USB 2.0 port and the Fysetc H36 to a USB 3.0 port, and vice versa. I even tried different combinations of ports on the same controller. But no matter what I tried, the result was the same: the Pi failed to boot when both devices were connected. This told me that the issue wasn't specific to a particular USB port or controller. It was something more general.

The Solution: A Simple USB 2.0 Hub

After hours of head-scratching and experimenting, I stumbled upon a solution that, in hindsight, seems almost too simple. But that's often how these things go, right? You bang your head against a wall for ages, and then the answer is staring you in the face.

The magic bullet? A simple, unpowered USB 2.0 hub. I connected both the Duet 2 and the Fysetc H36 to the hub, and then connected the hub to the Pi. And guess what? The Pi booted up perfectly! Every. Single. Time.

This was a huge relief, but it also raised a new question: Why did this work? What was it about the USB hub that solved the problem? This simple USB 2.0 hub solution indicates a boot-time USB enumeration conflict.

The Suspect: Boot-Time USB Enumeration Conflict

My best guess, based on the symptoms and the solution, is that the issue is a boot-time USB enumeration conflict in the Pi's firmware. Let's break that down:

• Boot-Time: The problem only happens during the boot process, not once the operating system is up and running.
• USB Enumeration: USB enumeration is the process where the Pi (or any computer) identifies and configures USB devices when they're connected. It's like the computer saying, "Hey, what are you? Oh, you're a Duet 2. Got it!" and then setting up the drivers and communication channels.
• Conflict: The Pi seems to be getting confused or overwhelmed when trying to enumerate both the Duet 2 and the Fysetc H36 simultaneously during boot.

The unpowered USB 2.0 hub likely acts as a kind of intermediary, buffering the enumeration process. It might be slowing things down slightly or presenting the devices to the Pi in a different way, giving the Pi's firmware a chance to sort things out. It's like the hub is acting as a traffic cop, managing the flow of USB device information during the critical boot phase.

Key Takeaways and Lessons Learned

So, what did we learn from this adventure? Here are some key takeaways:

1. Power is Paramount: Always ensure your Raspberry Pi has a stable and sufficient power supply. A weak PSU can cause all sorts of unpredictable behavior.
2. Firmware First: Keep your Pi's bootloader firmware up to date. It's a simple step that can often resolve compatibility issues.
3. USB Conflicts Happen: USB enumeration conflicts can be a real pain, especially during boot. If you're running into weird USB-related issues, consider a USB hub as a potential solution.
4. Divide and Conquer: When troubleshooting, try isolating the problem. In this case, disconnecting one device at a time helped narrow down the issue.
5. The Simple Solution: Sometimes, the solution is surprisingly simple. Don't overthink it! Troubleshooting raspberry pi 4 boot failure can sometimes lead to unexpected solutions.

Final Thoughts

This was definitely a frustrating problem to troubleshoot, but it was also a great learning experience. I hope this guide helps you if you ever run into a similar issue with your Raspberry Pi. Remember, the key is to be patient, methodical, and don't be afraid to try different things. And hey, if all else fails, a simple USB hub might just save the day! Happy tinkering, guys!