Can't connect an MKS Rumba32 board via USB

[Bernouillle]

Hello there!
I know, that the MKS Rumba32 board is not sold by your company, but maybe you can help me to solve my connection problem. I'm using Klipper as the firmware, where a Raspberry Pi is used as a host computer to do all the calculations and to communicate with the Rumba32 board. Unfortunately i am not able to find the USB connection of the Rumba32 board with the Raspberry. Do you have an idea how to fix this problem?
Many thanks in advance!

[czosnekltd]

I had the same issue with KLIPPER/MKSRumba32 and USB. Have you tried to connect via UART?
Can any of you provide a working KLIPPER config for motherboard MKS RUMBA32 or RUMBA32?

[Bernouillle]

@czosnekltd i haven't tried it yet. Can you tell me how i set up the UART connection between the Pi and the MKS Rumba32? Do i have to change something in the configuration file?

[czosnekltd]

I have not been able to connect via USB so far.
But the connection via the UART1 port (on GPIO) works.

  │ │                   [*] Enable extra low-level configuration options                                          │ │
  │ │                       Micro-controller Architecture (STMicroelectronics STM32)  --->                        │ │
  │ │                       Processor model (STM32F446)  --->                                                     │ │
  │ │                       Clock Reference (12 MHz crystal)  --->                                                │ │
  │ │                   [ ] Use USB for communication (instead of serial)                                         │ │
  │ │                   [ ] Use CAN for communication (instead of serial)                                         │ │
  │ │                       **Serial Port (USART1)  ---**>                                                            │ │
  │ │                   (250000) Baud rate for serial port                                                        │ │
  │ │                   [ ] Specify a custom step pulse duration                                                  │ │
  │ │                   ()  GPIO pins to set at micro-controller startup                                          │ │
  │ │

In section [MCU] in my case in RPI4:

[mcu]
serial: /dev/ttyS0
baud: 250000
restart_method: command

and Disable Linux serial console

(By default, the primary UART is assigned to the Linux console. If you wish to use the primary UART for other purposes, you must reconfigure Raspberry Pi OS. This can be done by using raspi-config):

Start raspi-config: `sudo raspi-config.`
Select option 5 - interfacing options.
Select option P6 - serial.
At the prompt Would you like a login shell to be accessible over serial? answer 'No'
At the prompt Would you like the serial port hardware to be enabled? answer 'Yes'
Exit raspi-config and reboot the Pi for changes to take effect.

[Bernouillle]

Thanks a lot for your help so far, @czosnekltd! I really appreciate it. I still have one question left. Which pins do i use for the UART connection on the RUMBA32? Are the TX/RX pins of the AUX connector the correct ones? And do i need a GND pin as well?

[czosnekltd]

I joined:
AUX-1/AUX_TX => RPI/GPIO_15(RXT)
AUX-1/AUX_RX => RPI/GPIO_14(TXT)
AUX-1/GND => RPI/GPIO_GND
The AUX-1 / AUXU_TX / RX outputs differ from EXP3 / USART1_TX / RX in that they are protected with additional resistors (looking at the schema diagram), so I think that in principle EXP-3 / USART1_TX / RX can also be connected.
But as I wrote at the beginning, I used pins on the AUX-port for safety.