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SB2040 Startup issue


New member

I’m having an issue on the mellow sb2040 can bus controller. There are two blue LEDs on the controller; one is a power light the other indicates the can-bus connection (I assume).
Normally, if I switch on my printer (V2.4) both LED are on immediately.

Sometimes only the power LED is on. When that happens I haven’t found any other solution then power cycling the printer until both led are on.
I don't know if I need to worry about that, are there any thoughts on this?

If the printer starts normal (Both LEDs are on) there is no other issue to the can-bus. I did several multi-hour prints without any connection problems.

This is satus of a current print

pi@mainsailos:~ $ ip -s link show can0
4: can0: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1024
RX: bytes packets errors dropped missed mcast
655008 106377 0 0 0 0
TX: bytes packets errors dropped carrier collsns
2168331 286091 0 0 0 0

This is my setup:

Voron 2.4r2 Formbot
Mellow SB2040
RPI4 with waveshare can-hat
Octopus with klipper FW (no canboot)

I’m using the cables that come with the mellow kit in the cable chain

Best regards
There is usually a delay between the Control board and the CAN board on startup. I will occasionally not restart the printer but I will restart klipper to help it connect.
I also do not have a good feeling in restarting the printer but everything I tried so far do not solve the issue. This incudes restarting klipper, moonraker and the Pi. I also tried some commands to stop and restart the can communication.

I also think it can be a timing issue between the start of the sb2040 and the PI. Next I will try to start the Pi explicitly before the sb2040 and vice versa. I hope I can find a condition that is causing the behavior.
Next time it happens grab the klipper log and post it. Might be able to spot something that is going on.
Of course, since I reported the problem, it hasn't happened again. If there is any news on this, I will post it here.

Murphy's general laws​

  • Nothing is as easy as it looks.
  • Everything takes longer than you think.
  • Anything that can go wrong will go wrong.
  • If there is a possibility of several things going wrong, the one that will cause the most damage will be the one to go wrong. Corollary: If there is a worse time for something to go wrong, it will happen then.
  • If anything simply cannot go wrong, it will anyway.
  • If you perceive that there are four possible ways in which a procedure can go wrong, and circumvent these, then a fifth way, unprepared for, will promptly develop.
  • Left to themselves, things tend to go from bad to worse.
  • If everything seems to be going well, you have obviously overlooked something.
  • Nature always sides with the hidden flaw.
  • Mother nature is a bitch.
  • It is impossible to make anything foolproof because fools are so ingenious.
  • Whenever you set out to do something, something else must be done first.
  • The Light at the end of the tunnel is only the light of an oncoming train.