Lost connection with MCU 'can0' | VORONDesign | Page 1

analog gull Feb 2, 2024, 5:52 PM

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My 2.4 uses an EBB36/U2C/Octopus 1.1. I have no issues unless I start a print that uses most of the bed (see attached). When I do start a full-bed print, my toolhead shuts down (lights/heat/fan all off, printer stays on) once it hits a specific spot near the top center of the bed. The error message comes up "Lost communication with MCU 'can0'"

At first I suspected my CANBus wire was coming loose at that point, but all my connections look solid and I haven't found any breaks in the wire. As you can see in that picture, the skirt prints fine, it's not until the actual print starts that the disconnect happens. No issues going over that spot during bed mesh or manually having the toolhead go there with the LCD controls, either. I don't have any issues with smaller prints in the center of the bed.

Any ideas?

grim sandal Feb 2, 2024, 6:19 PM

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Sounds like an intermittent break in the CAN wires. To make it easy, pull the CAN Cable and test the resistance. Should read 120 Ohms. Now bend and flex the cable at different points to see if the resistance goes high or goes open circuit. That should tell you where the break is, if that is the problem.

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pull the cable from the EBB while still connected to the U2C for the test

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And with the power off, obviously

analog gull Feb 2, 2024, 6:25 PM

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So, measure resistance between CAN-L and CAN-H at the ebb end?

grim sandal Feb 2, 2024, 6:26 PM

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yeah..... use the 120 Ohm resistor on the U2C board to help with the test

analog gull Feb 2, 2024, 6:28 PM

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Alright, thanks! I'm at work until this evening but I'll check it once I get home. I have an entirely new CAN cable coming next week (current one is homemade...) that should hopefully fix this whole issue but if I can get printing sooner it'd be all gravy.

analog gull Feb 3, 2024, 12:19 AM

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An update to this -- I measured the resistance in the cable this evening and I absolutely could not get it to go high resistance or open circuit. It was 120 ohms no matter how violently I kinked or jostled the cable. Going to check the solder joints on the EBB

grim sandal Feb 3, 2024, 1:31 AM

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Makes sense....... let me know how it goes....

analog gull Feb 3, 2024, 6:35 PM

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Welp, I think I solved the issue and it's dumber than I anticipated! I was only losing contact with the canbus on my toolhead at the top center of my print bed because the brass nozzle brush was grazing my euclid probe magnets and shorting them, so the EBB36 was shutting down.

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The first layer of my full-bed test print just layed down with no issues after removing the brush

#Lost connection with MCU 'can0'