Mini + RPi backpowering issue?
Hello,
I have Prusa Mini+ connected to Raspberry Pi 4 with OctoPi installed. RPi is powered by USB-C power adapter (5.1V/3A) connected to smart socket (Z-wave). There is only Raspberry Camera connected to RPi via CSI and small 2-pin fan powered by RPi's GPIOs.
My problem is, that even when smart socket is OFF, red power led on my RPi blinks every maybe 15-20 second. I thought it could be failing socket, but other socket from different manufacter is doing the same. When I unplug USB-C from RPi, blinking stops so it looks like backpowering issue, but Prusa Mini is OFF!
What can be the issue here?
Thank you.
RE: Mini + RPi backpowering issue?
In my experience, most smartsockets bleed thru a tiny bit of current even when "off".
To rule out the mini, unplug the rpi from mini but let it connected to the socket.
Prusa Mini+ kit. BondTech extruder. FW 5.1.2
Prusa MK3S+ kit. Stock. FW 3.11.0
Prusa MK3S+, used. Stock. FW 3.13.3
RE: Mini + RPi backpowering issue?
@mrstoned
Strangely enough, when Mini is unpluged, blinking stops.
RE: Mini + RPi backpowering issue?
@bigmikesk
Weird.
Does the blinking happens if you plug in something else that normally draws power, like a keyboard or mouse in place of the mini?
Prusa Mini+ kit. BondTech extruder. FW 5.1.2
Prusa MK3S+ kit. Stock. FW 3.11.0
Prusa MK3S+, used. Stock. FW 3.13.3
RE: Mini + RPi backpowering issue?
@mrstoned
I tried USB flah drive... RPi didn't blink. And I just noticed that when it blinks, that small fan it trying to spin as well. Fan is connected to GPIO-4 and GPIO-6.
RE: Mini + RPi backpowering issue?
@bigmikesk
I just thought of another test;
Plug the mini back in, but disconnects the mini's powersupply.
Prusa Mini+ kit. BondTech extruder. FW 5.1.2
Prusa MK3S+ kit. Stock. FW 3.11.0
Prusa MK3S+, used. Stock. FW 3.13.3
RE: Mini + RPi backpowering issue?
@mrstoned
When is Mini's PSU disconected, RPi didn't blink.
And it still blinks even when fan is disconnectd from RPi.
RE: Mini + RPi backpowering issue?
Unless they have changed the buddy board, it does not supply power though the micro usb by default. I found this out when I tried to do my setup to back feed power into a RPi 3A+ so I would only have one cable to the Pi. If you want to back feed power though the micro usb port, there is a solder pad bridge jumper on the bottom of the board that you need to bridge with a blob of solder.
My Mini is an original one that was delivered in late Aug 2020, Unknown if the Mini+ has a different buddy board, or maybe they have this solder pad jumper bridged from the factory now?
I don't think I would try back feeding power into a RPi 4, They've very power hungry. I am unsure what the max ma the Mini can supply though it's micro usb port, but I've measured the RPi 3A+ to consume around 100-200ma. I've had it powered by back feeding power for several months with no issues.
RE: Mini + RPi backpowering issue?
If you do want to check if that solder pad jumper is enabled/disabled. Remove your buddy board and check JP1 on the bottom. Bridging this is what enables the power though the micro usb. If they are enabling it from the factory now, then you should be able to just clean up the solder blob with some solder wick to disable the power though the micro usb.
RE: Mini + RPi backpowering issue?
I sure hope they aren't enabling this from the factory now, unless that port can safely provide the 2+ amps that the Pi4 requires. Otherwise you're going to have people plugging in the data cable from their Pi3 or newer boards which can be back fed power and the Pi will instantly power up if the data cable is connected before the power cable to the Pi.
If it can't support the 2+ amps, probably the least it would do is brown out the 5v rail on the buddy board and make the Mini crash. Worst case if the traces can't handle it, the board traces might turn into a fuse and burn out.
RE: Mini + RPi backpowering issue?
I tried USB cable with cuted-off red wire, but RPi is still blinking! 😩 So it is not a backpowering problem.
Any ideas?
Thank you.
RE: Mini + RPi backpowering issue?
Unless they have changed the buddy board, it does not supply power though the micro usb by default. I found this out when I tried to do my setup to back feed power into a RPi 3A+ so I would only have one cable to the Pi. If you want to back feed power though the micro usb port, there is a solder pad bridge jumper on the bottom of the board that you need to bridge with a blob of solder.
My Mini is an original one that was delivered in late Aug 2020, Unknown if the Mini+ has a different buddy board, or maybe they have this solder pad jumper bridged from the factory now?
I don't think I would try back feeding power into a RPi 4, They've very power hungry. I am unsure what the max ma the Mini can supply though it's micro usb port, but I've measured the RPi 3A+ to consume around 100-200ma. I've had it powered by back feeding power for several months with no issues.
interesting, I removed the 3a+ as I often get undervoltage error even with decent quality 2.5A power supply, now I'm using a 3.3 powered rpizero, but it's not the same thing...
RE: Mini + RPi backpowering issue?
I tried USB cable with cuted-off red wire, but RPi is still blinking! 😩 So it is not a backpowering problem.
Any ideas?
Thank you.
It can be only the smart socket feeding micro amps to the usbc, nothing else.