Prusa Connect and Filament Management (Spoolman)  

Prusa Connect and Filament Management (Spoolman)

I am new Core One owner and as so many other users I want to track my filament usage. Previously, I used a Klipper based printer with Spoolman. I was exploring options to use that with my Prusa printer and it turns out that this is harder than I expected.

This is exacerbated as my printer seems to stop responding to ethernet (and wifi) periodically. I so far had three support sessions on that with no progress except trying wireless hotspots, different routers, switches etc without success. At the same time other devices and the Buddy cam work well. Guess that is another topic.

I found those options:

1. Use FilaBridge. It connects to PrusaLink and updates Spoolman. You select the current spool in the UI. You have to do that before the end of the print. It will not warn you if your spool does not contain enough filament. By design it is somehow racy. If downloading the Gcode fails (or is too slow) it won't update Spoolman. If you start the next print to fast and it did not see the FINISHED state it will not update. With my somehow broken network on the printer this is not reliable at all. Also it neither will manual filament changes (via G-Code) or filament runouts. It cannot handle canceled job (will assume all filament has been used). Plus: It does not care how your print started (USB, PrusaConnect, PrusaLink)
2. Use Octoprint. This works pretty well in general. When printing via the Web UI you get a nice filament selection dialog and it will warn you if your spool does not contain enough filament. However, there seem to be serious limitations and numerous bugs between xBuddy and Octoprint. Buddy cam also requires some additional hacks to work. While this is more reliable (since ethernet and wifi on the RPi is super stable) it caused other issues and overall seems fragile. It will not work for prints directly via PrusaConnect/PrusaLink or via USB.
3. There are a few ESP32 based approaches with NFC readers which also use PrusaLink and suffer from similar issues as (1).
4. If you know any other option please let me know!

So how could we do better? What if we could get all the data we need from Prusa Connect? I looked into that and it seems possible. Here is how:

1. We can get the print history for each printer
2. For each job we can get events to see if any filament runouts/changes occured (code #31829) and when
3. Via the material_quantity api we can get the used material from start to changed and change to end (or even with between multiple changes). That also allows us to get an accurate filament usage for canceled jobs (unlike the PrusaConnect UI).

With that we can compile a list of jobs with filament usage (including manual changes and runouts). We can either select the spool in advance (like FilaBridge) or render a list where you can choose the used spools afterwards. Personally I would like to choose the spool in advance but to be able to correct mistakes later on (and it should fix that in Spoolman for me).

Downsides for that approach:
1. It only works for prints via PrusaConnect (PrusaLink, USB and serial are ignored).
2. PrusaConnect API is not officially documented/versioned and we rely on it. It might change and break stuff.
3. This probably won't work for toolchanger/INDX printers. The material_quantity API clusters by material. For the XL or INDX we would need on value per extruder.

I wrote a proof of concept script for this and based on my 176 prints it works extremely reliably and seems to be very accurate. Performance seems to be fine too. I will turn this into a small python web app for my personal use. Let me know if you are interested.

Ideally this would be part of PrusaConnect somehow (if you know how to make that happen let me know).