Random lost communication via usb

[yzheka]

When I setup connection via USB->Rpi 4 it can disconnect random midprint. But when I use UART, everything is working ok. I have tried different usb cables, does not help. It also disconnects until I press reset button on the board. After I press reset it connects normal. So I don't think it is cable issue.

[marcoa131]

Sounds like a ground loop problem, how is the pi and the board powered?

[yzheka]

@marcoa131 the board is powered via mw LRS 350 psu and the pi is powered via board's pins for rpi.

[marcoa131]

I understand that you're connecting the board and the pi through UART and the board is powering the PI because you're using the UART and power pins and that has been working for you.
But how were you powering the board and the PI when you were connecting the board via USB?

[yzheka]

@marcoa131 same way

[marcoa131]

I did some experiments with an Ender 3 running klipper using this board and a btt pi, both powered by the same 24v power supply. I had random disconects just like you. I solved it following this guide: https://community.octoprint.org/t/put-tape-on-the-5v-pin-why-and-how/13574
Also make sure to keep the 5v rail jumper on "DC5V" instead of "USB5V".

[yzheka]

Hmm, interesting solution, i will give a try, thank you.

[marcoa131]

A possible solution for you would also be changing the baud rate to 115200
you'll need to compile and reflash klipper to the board, but it has been successfull in my tests.

[yzheka]

A possible solution for you would also be changing the baud rate to 115200 you'll need to compile and reflash klipper to the board, but it has been successfull in my tests.

I have no issues with uart communication

[marcoa131]

you can also change baudrate with USB connection.

[SergiusFlavius]

I have successfully connected the board to the Raspberry Pi Zero 2 W (RPi) via USB and flashed the Klipper firmware.
Klipper firmware was compiled with Bootloader offset (No bootloader) option. The RPi was powered by an external 5V power source. I started seeing random disconnects and the board stopped connecting via USB.
I supposed to try connecting the RPi to the board via UART.

RPi	Board
p2 5V	DC5V
p6 GND	GND (left of PA10)
p8 GPIO14 (TXD)	PA10 UART-RX
p9 GND	GND (on top of PA9)
p10 GPIO15 (RXD)	PA9 UART-TX

Are the PA9, PA10, 3.3V and PRi pins safe?
How do I flash the new klipper firmware to the board to enable the UART?

[marcoa131]

I have successfully connected the board to the Raspberry Pi Zero 2 W (RPi) via USB and flashed the Klipper firmware. Klipper firmware was compiled with Bootloader offset (No bootloader) option. The RPi was powered by an external 5V power source. I started seeing random disconnects and the board stopped connecting via USB. I supposed to try connecting the RPi to the board via UART.

RPi Board
p2 5V DC5V
p6 GND GND (left of PA10)
p8 GPIO14 (TXD) PA10 UART-RX
p9 GND GND (on top of PA9)
p10 GPIO15 (RXD) PA9 UART-TX
Are the PA9, PA10, 3.3V and PRi pins safe? How do I flash the new klipper firmware to the board to enable the UART?

To enable the UART interface on the cheetah v3, put your board into DFU mode as usual and flash it with the make menu-config you posted, compile and flash through the USB port as usual. Every option in the print you sent is correct, the only thing you need to change from USB to UART is the communication interface.
Yes, the board pins are RPI safe, you only need to connect ground, 5v, PA9 and PA10 to the respective pins on the RPI GPIO.
Let me know how it works out for you and if you have any other questions.