I purchased a Raspberry Pi 4 Model B to use as the server for the eVOLVER I’m building, but I was at a loss on how to set it up to run the python server code given on the github page. @bgwong was kind enough to send me a disk image that I could flash to an SD card and plug straight into the Raspberry Pi. The server is now successfully booting and the lab computer application is recognizing and connecting to it, but there was an issue I ran into along the way, so I want to share my troubleshooting in case someone else ends up having the same problem.
The Problem: Trying to use a RPi4b to boot into a disk image from an earlier model.
What the Problem Looked Like: Turning the RPi4b on with the server SD card in, the green LED would flicker for a couple seconds then nothing. It wouldn’t output anything to any connected monitor. In contrast, the RPi4b would display the correct descriptive error prompts if I turned it on without an SD card or with a blank SD card, and it would boot up successfully on a copy of Raspberry Pi OS Lite downloaded from raspberrypi.org and flashed to the SD card in an identical manner.
The Solution: Adding the appropriate RPi4-specific boot files into the boot partition of the server SD card.
The Specifics for My Situation: I figured the issue was somewhere in the boot files because the bootloader was functioning correctly otherwise. In comparing the boot partitions between the server SD card and the functioning Raspberry Pi OS Lite card, I found the boot partition in the server SD card was missing several files:
bcm2711-rpi-4-b.dtb
fixup4.dat, fixup4c.dat, fixup4db.dat, fixup4x.dat
start4.elf, start4c.elf, start4db.elf, start4x.elf
kernel7l.img (32-bit kernel for RPi4)
kernel8.img (64-bit kernel for RPi4)
Copying these files from the functioning copy of Raspberry Pi OS Lite to the boot partition of the server SD card enabled my RPi4b to boot up and interface with the lab computer successfully. Having never used a Raspberry Pi or linux machine before, I can’t speak to the reasons behind this or the advisability of doing this, so maybe someone experienced can provide more general guidance for this type of issue.