Skr pro to rpi4 wiring

Apart from connecting usb(skr pro) to usb(rpi4).
Can I connect the 2 boards internally?
Like usb header(skr pro) to usb header(rpi4). Instead of using a usb cable between the 2 boards

Technically, there are ways to do this, but I don’t know if Octoprint supports it properly or not.

There are 3 UART ports in the SKR Pro. One is the same that connects to the USB and also has a 4 pin header in the corner of the board. Use of this one will preclude connection via USB, but works well. If you get the module that alloes the SKR Pro to ru RepRap Firmware and the Duet Web Control, it connects to this header, as well as the 2 ports for the 12864 LCD. (You don’t need this module, it’s just an example of use.)

The second is the UART that the TFT35 connects to. This is enabled in the V1 firmware, so is a viable choice if you aren’t running the TFT35. This does still allow use of a 12864 LCD controller for Marlin mode.

The third is the WIFI port for thr ESP01S module, which I believe is now enabled for use.

Any of these can be wired via a 4 pin cable to the Raspberry Pi GPIO UART. The Raspberry Pi will need to be set up to communicate through that UART instead of the USB Serial device. I do not know how to get Octoprint or cnc.js to do that.

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The pi has a gpio uart. By default, it (at least used to be) set up as the console for linux. You can disable that with raspi config (and octopi might already do that). Octoprint also ignores that serial port in its config. There is an option in the settings to re-enable it.

You can then wire that uart to the skr, on the same wires the tft uses.

But I don’t recommend doing that. The usb protocol has error checking, checksums, acks/nacks, and it is more reliable than the uart over wires connection. It seems weird, but the USB will be more reliable than uart.

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I don’t know about the SKR Pro, but I’ve been running a SKR Pico (in a Voron v0) over a UART connection with no issue. Plan to try the same on my LR3 to avoid the additional external wire.

Are you referring to these four?