Octoprint with Raspberry Pi3 B+ USB vs GPIO connection  

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matthew.p26
(@matthew-p26)
New Member

What's the benefit/difference of connecting octoprint via the J19 connector vs USB? (I'm using USB right now)

USB = USB Serial converter

Connection info from:
https://shop.prusa3d.com/forum/others-archive--f66/connecting-raspberry-pi-3-to-einsy-headers-t12394-s20.html#p123126

J19 =
2 Pins: serial rx/tx 6,8
2 pins: Power/ground 2,4

2 pins: ??? 13,14

Q1: What's the use/benefit of the 2 extra pins over USB connection?

Q2: Do I have to install/configure something extra in Octoprint, for octoprint to use these extra 2 pins for whatever they do??

Q3: Does serial via USB or Serial via GPIO provide any benefits?

https://github.com/ultimachine/Einsy-Rambo/blob/1.1a/board/Project%20Outputs/Schematic%20Prints_Einsy%20Rambo_1.1a.PDF

makes it look like 13,14 are for reset, and ground. Though it also shows "Pins 9-14 also function as ICSP for U2, Atmega 2560" Perhaps they're in software to do something.. I'm having a hard time trying to figure out what

Posted : 14/04/2019 7:13 pm
Bunny Science
(@bunny-science)
Noble Member

Some wish to use the GPIO connection and EINSY power to avoid another power supply. However, I would like to point out a benefit of using USB and a separate power supply.

I often power down the printer to perform work on the motors. Because my Raspberry Pi is on its own power, I don't have to wait through a long Pi and Octoprint reboot each time the printer is shut off. Octopi simply keeps running while the printer is off. If my Pi were on printer power, the delay would be annoying.

Posted : 14/04/2019 8:00 pm
vintagepc
(@vintagepc)
Noble Member

(note you cannot run a B+ with power supplied from the Einsy, it cannot supply the required current.)

Posted : 14/04/2019 8:53 pm
luke.m8
(@luke-m8)
Active Member

So the only difference between USB and using GPIO is the need for an extra power supply?

All other functionality is the same?

Posted : 24/04/2019 6:35 pm
vintagepc
(@vintagepc)
Noble Member
Posted by: luke.m8

So the only difference between USB and using GPIO is the need for an extra power supply?

All other functionality is the same?

You will still need a separate power supply regardless of the option you choose. GPIO cannot supply enough current for the B+.

Posted : 24/04/2019 6:53 pm
luke.m8
(@luke-m8)
Active Member

Thanks!

Posted : 24/04/2019 6:55 pm
Migamix
(@migamix)
Trusted Member

as long as you DO NOT connect the 5v pin to the einsy , the gpio route seems better IMHO yes, an external wall wart for a pi3 will be needed, but you will be happy with that as a setup

keep ground pin 

and we’ll be saying a big hello to all intelligent life forms everywhere … and to everyone else out there, the secret is to bang the rocks together, guys....
Posted : 05/05/2019 12:28 am
BMac1203
(@bmac1203)
Active Member

I am running a RPi3 A+ && Pi Cam via GPIO pins on the Einsy with no problem, whatsoever (power requirements for A+ are lower).

Pi is in a case mounted to the 3030 rail below the control box with a custom connector cable attaching the Pi to the Einsy.

 

I have had all sorts of Pi setups in the past, most recently a 3B+ running on its own power supply and controlling things via 4 DC relays. It was great to be able to turn the printer on/off, lights, fans, etc. but I just wanted simplicity with my Prusa (my other printer(s) are for tinkering).

Powering off isn't a big deal. I open the Octoprint app on my phone and tap "Shutdown" and by the time I put down my phone the Pi has powered down. When I turn the printer back on, same thing. Octoprint is already up, running and connected by the time I'm able to load the server page to get a print going.

www.littleredtoaster.com...
Posted : 08/05/2019 9:49 pm
jab416171
(@jab416171)
New Member

Can you elaborate on this 'custom connector cable' that you're using?

Posted : 09/05/2019 5:02 am
matthew.p26
(@matthew-p26)
New Member

I guess we don't know what the 2 extra pins that are connected via the header vs USB are for?

2 pins in J19 connector.    13,14     Is it a reset and ground pin?  What triggers octoprint to do anything on these pins?

Posted : 19/05/2019 4:56 pm
messismore
(@messismore)
Active Member
Posted by: Migamix

as long as you DO NOT connect the 5v pin to the einsy , the gpio route seems better IMHO yes, an external wall wart for a pi3 will be needed, but you will be happy with that as a setup

keep ground pin 

What's the advantage of this? The free Usb port?

Posted : 06/07/2019 2:34 pm
BMac1203
(@bmac1203)
Active Member

If you use a 3A+ you don’t need the separate power supply, so you’d be getting your USB port back, using the Einsy GPIO and quicker Octoprint.

So you can tastefully mount your rPi and run a single cable to your MK3/S control box for power/data.

 

 

www.littleredtoaster.com...
Posted : 06/07/2019 7:24 pm
spiff72
(@spiff72)
Trusted Member

I know this is an older thread, but I was curious about the extra 2 pins as well (they appear to be GPIO 3 and 4 on the Pi). Are these "REQUIRED" for a direct serial connection?  I checked the schematic of the einsy board and it appears that one of those pins is connected to ground on the einsy (this connects to GPIO 4, I think).  The other pin (connected to GPIO 3) looks like it is connected to a reset line through a transistor.

Posted : 23/04/2020 6:45 pm
spiff72
(@spiff72)
Trusted Member

Here is a screen grab of the relevant schematic section.

Posted : 23/04/2020 6:45 pm
GGFuzzy
(@ggfuzzy)
New Member

@littleredtoaster

Can you elaborate on what you had to do to get the serial communications working between the Einsy board and the Pi3 B+? I have the external USB cable solution working, but when I connect GND, TX and RX pins between the 2 boards (separate power) and turn on RPi port in MK3S settings, octoprint can't connect to the printer. Do I need the extra 2 GPIO pins connected as well?  Can't figure this one out and can't get a clear answer from the message boards (yet.) 

Posted : 29/05/2020 1:15 am
Bmart
(@bmart)
New Member

@littleredtoaster

Hey, I just saw your cable on Ebay which brought me to here. Let me first say I am very new to all of this so please go easy on me. I want to get octoprint working with my mk3s which is still on its way to me. The only good guides I see for setting up octoprint are using the pi zero which seems to be garbage. So I am happy to get a pi 3 but every mount I see that is printable for the pi 3 is for the b+. Being that I don't think I will need all those USB ports and the lower output is exactly what I am going for. I would be happy to buy your cable. Can you maybe point me to a guide that has exactly the setup you have? I love the picture you have above. It looks clean and easy to use. I purchased the pi camera and would loved to get it all ready to go before the printer comes in. Thanks!

Posted : 01/06/2020 6:41 pm
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