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Try to connect Raspberry Pi4 with the Prusa Mk3s

What is the problem?
The connection to ocotprint works. so the Raspberry boot up. Thats not the problem.
But now the Problem is the connection to the printer. I use the serial Port of the Prusa Mk3s ("/dev/ttyAMA0").
But if i try to connect, there is no reaction.

What did you already try to solve it?
Check that the Port "RPI" from the printer is on
Logs (syslog, dmesg, ... no logs, no support)
octoprint.log 108.5KB 25.11.2019 20:56 |
plugin_pluginmanager_console.log - 25.11.2019 19:22 |
plugin_softwareupdate_console.log - 25.11.2019 19:22 |
serial.log 296.0bytes 25.11.2019 20:55 |
serial.log.2019-11-25_18-52-36 1.5KB 25.11.2019 19:52 |
serial.log.2019-11-25_19-02-28 740.0bytes 25.11.2019 20:02 |
serial.log.2019-11-25_19-15-25 592.0bytes 25.11.2019 20:15 |

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Additional information about your network (Hardware you are trying to connect to, hardware you are trying to connect from, router, access point, used operating systems, ...)

Thank you for the help!

Hello @Paule79!

You tried to share the logs by copy and pasting the entry of the logging window, but by this way, no logs are copied...

Hello Thanks. Sorry, thats new for me. The logs are:
octoprint.log (112.1 KB)

you should putt the RPI to OFF on Prusa screen

1 Like

Any update on this? Are you connecting via serial port on the Einsy Rambo board or via USB? I have a Pi4 and can connect via USB but not serial port. Any ideas how to connect Pi4 via serial port?

I am having this same issue. I am running power direct to the Pi4 8gb, then wiring up the four connections needed for the serial communication (I think).

No matter what I do I cannot get OctoPrint to connect. Yes, I have edited the /boot/config.txt and /boot/cmdline.txt

Here are my latest logs serial (1).log (3.9 KB)

Also it should be noted that I get funky text on the Prusa screen once the Pi attempts to connect. All I can think is that I actually need to wire up the 5v as well?? Seems redundant to the plugged in power supply.

Have you have connected the grounds together?

No, I didn't. I will test that.

Ok, I wired that up and now I get Error: Could not write to serial port. So, that's progress at least :slight_smile:

Here is the log for that one serial (3).log (2.1 KB)

I tried enablign and disabling the RPi port on the printer. That did not seem to make any difference. Is it required that I wire up the +5v? I had assumed that with external power I didn't have to do anything different.

I would have assumed the same thing here, but maybe the circuit has to be completed on the serial bus for it to register a connection for some reason. Don't know from experience but just spit balling ideas.

I can't fry it by giving it another 5v source can I? I'm guessing they designed these to be "smart" enough to handle that?

I wouldn't risk it.

hmmm...but I so badly want to fix it :slight_smile:. This thing is 500x faster than my Pi Zero!

I was just looking to see if there were any differences in the serial pins on 4 or not, I wouldn't think they would have changed that.

Yeah, I already checked the GPIO info and the pinout seems exactly the same. The only thing that is maybe slightly weird is that there is a fan plugged into pins 4 and 6.

https://www.raspberrypi.org/documentation/usage/gpio/

I wonder if @TxBillbr might have an idea because I know he's pretty involved with Pi 4 and some of this stuff.

I really wish I would have known that the 8GB board was 64bit. I should have realized but you don't even think about it now that we've been on 64bit x86 for so long. I'm feeling like this thing is more headache than value right now.

OK, it has to be something with the Pi4 8GB. I wired it such that the 5v was coming from the einsy and not the external PSU and it still fails. The Pi is very responsive from the 5v provided by the einsy, but I still cannot connect to the serial connection.

I plugged my Pi Zero back in and it is working as slow as ever :confused:. I have no idea what could be different as the Pi4 8GB doesn't list any changes to the GPIO.

There is one difference I had assumed was not relevant, but maybe it is. On my Pi Zero I get a serial port of /dev/ttyAMA0 whereas on the Pi4 8GB I get a port called /dev/ttyS0.

Pi Zero Serial Screen

Pi4 8GB Serial Screen

OK, it works if I manually enter in /dev/ttyAMA0.

There must be something off with this board of the logic in OctoPrint. At least I can start experimenting with this.

There have been a couple of firmware changes on my Prusa that seem to have affected the connecting of OctoPrint.

  1. I have had to explicitly put the device in the port to open field in OctoPrint.
  2. It seems that the connection (which causes a reset on the printer) needs to wait before trying to connect.

So autoconnect is not working at all for me. I chalked it up to the number of things I have going on with mine (I only have a 4GB model). I run OctoDash as well as the Tasmoda power control. I have heard that the 8GB pi has some quirky issues. Just so you know, enabling and disabling the USB on the Prusa controls whether the internal usb port is on or not. Prusa made a way to mount a Pi0W directly to the Einsy on the MK3S. I haven't ever tried to run both the external and internal at the same time. I don't know if they share any circuitry or not.

As to the power, I would not put any additional power into the MK3S! Not even with the grounds tied together. The power on the internal connector is provided by a VERY small buck that it capable of running a pi0. I reread all fo the issue discussed here and am concerned you may have clobbered something on the Einsy. I use a 5V-lift board to prevent driving the printer from the USB.

Edit. I am confused on the direct connect. The printer cannot drive the pi power. If I understand correctly you have external power on the pi. You are trying to direct connect the serial? I would prove to yourself that the "normal" way of connecting works fine before embarking on a direct-connect. Power the pi via a official pi power adapter and hook a good quality usb cable between them. Once that works, you will know if you have a board problem. If you do choose to direct connect the serial, you must have a GND connected. The minimal serial connection requires GND, TX, and RX. I am thinking that the other GPIO pins they connect may be RTS/CTS, but I don't know without doing some more research.