Power between Raspberry PI and Duetwifi
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Can there be a power feedback between the two?
Is there a way to turn off the power on the USB ports of the Raspberry PI or is there a duet command to not except the power on the micro USB port, or it does not matter.
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are you talking about grounding loops?
if you power the pi via a step down converter from the same power supply as the duet, there will not be a grounding loop.
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I'm more worried about excess current draw from the PI, even using the same power supply.
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here is a list of max power draw for the pis
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@racenviper said in Power between Raspberry PI and Duetwifi:
Is there a way to turn off the power on the USB ports of the Raspberry PI or is there a duet command to not except the power on the micro USB port,
No, and no. You could make a usb cable with only d+, d- and gnd if you're concerned. If I recall correctly there is a diode between 5v from the usb and the duets internal 5v (schematics are freely available to confirm).
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the duets internal 5v is not enough to power a pi.
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@veti A PI USB port will power a Duet, Display and everything else attached to a Duet.
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@bearer Actually you can, I just don't know how to use it. https://github.com/codazoda/hub-ctrl.c/wiki/Raspberry-Pi
All USB port except for USB port 1, the power can be turned on or off.
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@racenviper said in Power between Raspberry PI and Duetwifi:
A PI USB port will power a Duet, Display and everything else attached to a Duet.
no. the hotend alone would be way to much for the pi usb port.
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Yep, Max out current and a voltage drop, what effect is that going to have on the Duet and or the PI.
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@racenviper interesting, i stand corrected, didn't try that on the 3b+ but seems to work, have not had success with it in the past. On the other hand you'd have to add this to systemd or rc.local and it would be some time between power on of the Pi and the USB port getting powered off, so if there is a real concern I'd hesitate to call it a solution.
(was a little disappointed as the wiki suggested you could disable data for a given port, but it must be a typo, that would also have been handy. but discovered f.ex.
echo 0 > /sys/bus/usb/devices/2-1.5/authorizedto acheive the same thing) -
Hmm, initial test caused the usb hub to lock up, ignoring any connects or disconnects, but I just flashed the Duet from the Pi without USB power from the Pi. Could be the CH340 driver from the other device I tried with that caused the issue. Ymmw.
Worth noting that it seems "port 2" is connceted to another USB hub that powers all 4 usb ports on the 3B+ as only
-P 2has any effect, and it affects all 4 ports at the same time.
