How is the M3 wired to the Raspberry PI?

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Mach
Posts: 63
Joined: Sun Nov 29, 2015 1:05 am

How is the M3 wired to the Raspberry PI?

Post by Mach » Mon May 04, 2020 11:02 am

I see that the M3 has an integrated Raspberry PI for octoprint next to the Rambo board housing. It does not appear to be connected through the USB port. So how is it connected?

whoDat
Posts: 5
Joined: Tue Apr 29, 2014 3:53 pm

Re: How is the M3 wired to the Raspberry PI?

Post by whoDat » Tue May 05, 2020 5:52 am

It's connected via serial port connection ( /dev/ttyS0 ). You can see this in the Octoprint settings under the "Serial Connection" section. The rx/tx pins for this are on the GPIO header of the Raspberry Pi.

http://www.anintegratedworld.com/wp-con ... 08/pin.jpg

wh0dat

Mach
Posts: 63
Joined: Sun Nov 29, 2015 1:05 am

Re: How is the M3 wired to the Raspberry PI?

Post by Mach » Tue May 05, 2020 3:53 pm

Thanks for that. I spoke with support yesterday. There is apparently a daughter board in the mix that is not available as an upgrade. I'm assuming its a level converter to change from 5v to 3.3v for TX/RX pins. Not sure how the 5v power is being tapped to power the PI. It appears to be powered from the PSU. My plan is to use the GPIO header from a voltage regulator tapped to the PSU. It skips the polyfuse but should be ok downstream of the voltage regulator.

Edit: a follow-up on this one - got everything wired to test on separate power supplies. It worked intermittently on /dev/ttyAMA0. I'm guessing its noise and will re-try once the PSU is wired in. Otherwise, I'm going to punt on this idea and just get a short right angle USB cable.

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