I have connected my Raspberry Pi 3B to the mainboard with jumper cables via direct serial over the LCD’s Tx and Rx pins, but for some reason, Im only able to get a connection when I also power the pi via the nearby 5v and ground pins in the same LCD header.
When I disconnect the 5v/ground jumpers and power the pi via an external usb power supply I get the mcu connection error.
If the 5v rail of the printers mainboard supplied enough current to sufficiently power the pi then this would be no issue and id actually prefer to just have the single cable running to the pi for power and comms but I keep getting an undervoltage warning and am apprehensive of ignoring it, save myself the hassle of stability issues down the line.
Despite not having any power hungry HID’s connected to the pi that would surely require the full 5.1v 3a available power, I still dont feel confident under-powering it given the rapid rate of data transfer that will take place under full load while printing.
But are my assumptions wrong?
is klippers workload relatively lightweight or otherwise unimpaired by some degree of under-voltage?
better yet, does anyone know the actual current output from the 5v pin of the LCD header in a Creality 4.2.2 board? (my multimeter is blown I cant measure amperage atm otherwise id check myself)
After tireless efforts, for the life of me I thought the board was dead, wiring the Pi through serial interface is what finally allowed me to establish communication with the printer and verify that the firmware had actually flashed successfully. I already planned to connect over serial down the line anyway though since it looks neater than having so many usb cables dangling about
Thank you for the info and yes, you have understood me correctly.
Are you alluding that if I power the Pi via usb externally while simultaneously leaving the ground header connected between the board and the pi, that will solve my issue?
Would that introduce some sort of ground loop feedback noise into the circuit if I wired it this way?
Whats the easiest alternative to power the pi while connected via serial other than using a buck converter since i’ll have to wait a while if I ordered one and Id rather not, I have a range of common IC components on hand if necessary.
I just came to this website (new user) because I am having similar problems. I cannot get my Pi to talk to my Octopus v1.0.
Any I understanding this correctly?
If I connect UART to the Octopus from my Pi and then power my Pi with USB that I would also need to have a wire from the GND pin on the Pi to the GND Pin on the Octopus?
That is so interesting. I have been racking my brain and going crazy for a week now trying to get these 2 devices to connect via serial. No-one nor any document I have read stated this.
I feel this is the kind of information that should be in your face from the beginning.
I only started exploring the UART method because no matter what I try I cannot get them to talk over usb.
I wonder if connecting a GND between the 2 would make the usb work. but mine is a Voron and goes from 120V to 24V Meanwell. from 24v to 5V meanwell. Pi is powered from the 5V and MCU from the 24V but the 5V and 24V share a GND.
Sadly, in my case this (Adding a GND wire while powered by USB and using USB UART) did not solve the problem. So this morning I am going to try out UART connections with a Self Powered Pi.
Well, for me I finally got a tad bit further. I took the advice here and connected my Pi via UART with a GND wire between the two. and took out the usb cable. Pi is self powered, but now I get an error of timeout during connect.
So made it one step further.
So I took your advice and plugged a dedicated power supply into the pi, removed the 5v jumper cable and left the ground Rx and TX.
After turning on I couldn’t connect to pi over ssh, even with nothing plugged in.
took the pi over to a monitor and keyboard and now all im getting is a rainbow screen from the pi…
What could be the issue here??
I’m worried i’ve killed the pi…
After a bit of testing and frustration I figured out that the pi itself isn’t bricked thankfully, but the sd card became unresponsive, there goes hours of setup and calibration I guess…
