Can't connect to two Ender 3's over USB at the same time

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1

What is the problem?

Can't connect to two Ender 3's over USB at the same time

I have four printers, two mendelmax printers and two Ender 3s with stock firmware. I have two octoprints setup on a PC for the two mendel max printers and can print from both at the same time, they connect to /dev/ttyACM0 and /dev/ttyACM1. When I plug the two Enders in they connect to /dev/ttyUSB0 and /dev/ttyUSB1 but I can only connect to one at a time. If I connect to printer 1, then open my second octoprint and it refuses to connect, same happens when I switch.

Anyone have any idea why that is? Is there something about the Ender boards that conflict with each other over USB so you can't connect to two from the same computer?

On the second connection it seems to receive a bunch of temperature data before shutting down - not sure which printer is giving that info. Here is the log:

Connecting to: /dev/ttyUSB1
Changing monitoring state from "Offline" to "Opening serial port"
Connected to: Serial<id=0x7f9708768510, open=True>(port='/dev/ttyUSB1', baudrate=115200, bytesize=8, parity='N', stopbits=1, timeout=10.0, xonxoff=False, rtscts=False, dsrdtr=False), starting monitor
Changing monitoring state from "Opening serial port" to "Connecting"
Send: N0 M110 N0*125
Recv: o
Recv: :20.62 /0.00 B:20.62 /0.00 @:0B@T:20.62 /0.00 B:20.62 /0.00 @:0 B@:0
Recv: B@:0
Recv: T:20.62 /0.00 B:20.62 /0.00 @:0 B@:0
Recv: T:20.62 /0.00 B:20.62 /0.00 @:0 B@:0

[... snipped ...]

Recv: T:20.62 /0.00 B:20.51 /0.00 @:0 B@:0
Recv: T:20.62 /0.00 B:20.62 /0.00 @:0 B@:0
Unexpected error while reading serial port, please consult octoprint.log for details: SerialException: 'device reports readiness to read but returned no data (device disconnected or multiple access on port?)' @ comm.py:_readline:2605
Please see https://faq.octoprint.org/serialerror for possible reasons of this.
Changing monitoring state from "Connecting" to "Offline (Error: SerialException: 'device reports readiness to read but returned no data (device disconnected or multiple access on port?)' @ comm.py:_readline:2605)"
Connection closed, closing down monitor

I'm using Octoprint Version 1.3.10.

2

Not many of us here support more-than-one-printer-per-instance of OctoPrint, to be honest (especially on the Pi).

But you've indicated that you're hosting from a PC at least. Try searching the forum for "multiple printer" and read some of the work that others have done to try to make this work.