In the meantime, I've tried updating Octoprint to v1.4.2, which didn't seem to do anything.
Demonstration here: https://i.imgur.com/722WNW3.mp4
Since the last post, the error message in the web interface has changed to "Offline (Error: No more candidates to test, and no working port/baudrate combination detected.)"
Additional information about your setup
Raspberry Pi 3B+
Ender 3 Pro
1.1.5 Creality Silent Motherboard
There's been several reports of this lately it seems from the same printer. It's really starting to sound like a problem with either the design of the board or some other firmware related glitch. Below link is an example.
Maybe it would be smart for all you guys to keep your posts together for better troubleshooting...
Just a thought but do you turn on the printer first before the pi? The Ender 3 v2 doesn’t like the pi providing 5 vols down the usb cable.
When I have had a problem with connection to a pc I have found connecting to a iPad first usually resolves the issue
Out of desperation, I went ahead and bought a couple extension cables just to try this out. When connecting it to my Windows 10 PC it simply does nothing. I can't see the printer in Cura, I can't connect to it in the Arduino IDE to update the Firmware as someone suggested and when I go into the device manager, it only shows 'COM1' under ports. Is there a step I'm missing or could it simply be that the mainboard is defective?
I'm the happy owner of a Ender 3D pro which I like to call a V2 because it came with the motherboard of a v2. I'd be silly to give you advice regarding my own experience without checking we actually have the same hardware, so I have to ask : what made you call your Ender 3 Pro "a v2" ? The post you linked deals with a 1.1.5 card, which is a 8 bit. The motherboard I have is a 4.2.2, which is a 32 bit card. As far as I know, Octoprint works with both, but I don't want to tell wrongly that we share the same hardware if we don't.
After many troubles with EMI, I finally managed to connect my printer with Octopi. I've troubleshooted all of this here. My solution was, finally, to power the Pi from the Printer, and to put some strap on the USB cable as you mentionned.
I still have a question, just to be sure I understand the workflow. The screen you share on your initial post is really messy. When you plug the USB, the screen goes from a normal ender 3 screen to this messy-full-of-noise one ? When you don't plug any USB, the screen is clear and you can make clean print from the SD Card, right ?
Don't all USB cables have the same standardized 4 pins? As for applications, I restarted my PC multiple times, it shouldn't have an impact. And shouldn't the device manager show something, regardless of the baudrate?
The printer works perfectly fine, unless I connect the Raspberry Pi to the printer, which produces the seemingly random artifacts in the video. Connecting my PC to it on the other hand does absolutely nothing.
What do you mean by powering the Pi from the printer? Soldering the Pi's power supply cable to the internal pins of the printer's PSU?
Yep, USB cables are standard in connector's shape but not all are equivalent in the connection. Some uses better cobbler than others, shielding may vary too and, as @Hartmut_DK5LH said, some cables have only 2 out of 4 internal cable (the + and -, not the data line). Some are charging cables, others are data cables …
It goes the same with power source unit for raspberry pi. Some are better than others. I've tried using official power source for raspberry pi but it did not work so what I did at the end is, as you said, soldering a small circuitry (namely, a LM2596) to power the pi from my printer (note: I'm a total rookie in that, and still it was very easy). It was not about modifying the printer, actually – I didn't have to unscrew a single screw of the printer, I used a Y-shaped XT60 cable, if you wanna look on the net ;). "Chargers" sold on Amazon are generally cheaper than real power source units (which have to be precise in their current delivering; a USB charger does not really have too, I learnt).
But first things first, I'd probably try to get the connection to a computer working. I'd probably try different USB cable on a standard computer until I get a serial line to the printer, to rule out the raspberry pi.
You're a life saver. Out of the three cables I tried before none apparently were data cables, but knowing that the difference exists, I found the thickest (and unfortunately, also the shortest) cable I had lying around and using it, the connection works perfectly fine.
I then tried connecting the Pi to the printer with it, which resulted in the same artifacts as before. So, I once again taped over the 5V pin, as I had done with the charging cables and the artifacts disappeared.
I can now control the printer via octopi, as should be, BUT the printer still randomly clicks through the menus while the Pi is connected. I think I will try to update the firmware again and hope for the best.
I can't get it to work since I get an 'not in sync' error from avrdude everytime I attempt to upload firmware, no matter whether via the Raspberry Pi or my PC. No idea what causes this and I can't seem to find a working solution for it on the Internet.
The clicking also remains and is starting to drive me nuts.