RPi3 do not boot with two connected MCU's

General Discussion
1

Basic Information:

Printer Model: ZAV
MCU / Printerboard: SKR 1.3 and EBB42
Host / SBC Raspberry Pi 3B+
klippy.log
klippy (1).log (3.7 MB)

My RPi don’t boot when both SKR1.3 and EBB42 connected via USB. When i disconnect one of MCU’s, PRi boots fine and then i can connect second MCU firmware restart and all works fine next. But sometimes RPi can freeze when i do a firmware restart when saving config for example. And i need do all steps again. Remove one of the MCU’s USB(or turn of power for them), reboot RPi, turn MCU on.
I tried different cables for both MCU’s and different sequence of actions but nothing helps. Both MCU’s has no VBUS jumpers and powered from separate from RPi power supply.
How can i solve this?
Next i planned to install USB Eddy on my printer but want to solve problem first.

2

This seems strange. I already had up to 4 USB connected boards on a single RPi 3B and never experienced such behavior.

No idea, but it could point to some hardware defects. I’d try to connect a screen to the RPi and monitor the boot process to see where it fails.
In addition, you can check your Linux system logs and dmesg output.

Note that diagnosing this on a Linux system level requires some Linux admin knowledge. You might find some pointer in this discussion: Pi crashed 3 times mid-print, almost same place - #15 by Sineos

3

When i plugged in display to RPi with both connected MCU’s PRi don’t want boot at all.
But when i reboot or shutdown from console and then power up PRi it’s boot normal.
Problem arises when i power up both RPi and MCU’s power supplies at the same time. In this case even there is no backlight on connected keyboard. To start again in this case i need to power off MCU’s power supply or disconnect one of MCU and repower PRi.

4

I think I found the problem. With SKR 1.3 from another printer all works fine. RPi boot normal and no more freezes.

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5

Or not :frowning:
Still have strange behavior of all system

6

Now when RPi boot and work when i plug SKR to RPi it’s freeze.

7

Something like back-powering issues and both draw too much power from the Pi?

8

This is really quite unusual and in my opinion can only have two reasons:

  1. Some hardware defect
  2. Some really strange electrical stuff that causes, e.g. high ground potentials between the devices

Try putting an active (powered) USB hub between the RPi and the boards.

9

Still very strange behavior of all system. Only well working sequence of actions is first to power on RPi and after some time power on PSU of MCUs. I this case all works fine.
I think to try connect SKR with GPIO. Maybe it solves the problem.

10

Connection SKR to RPi with GPIO didn’t solve the problem. RPi still don’t want to start when i power on RPi and MCUs power supplies at the same time.

11

Replaced RPi to OrangePi PC and all works fine. OPi boots normal in any sequence of powering.

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12

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