# What UART port to use for RPi GPIO pins on an SKR v1.3 board

I have a Bigtreetech SKR v1.3, and I'm trying to connect a Raspberry Pi to the board using the RPi's GPIO pins as opposed to using a USB connection because space is limited within the case of CR10S Pro.

I watched this youtube video where he explains using the Z min and Z max endstops to connect to a RPi via the GPIO pins on a Raspberry Pi, and I've watched the video several times, but havent been able to get OctoPrint to connect to the SKR v1.3 board.

There is a dedicated UART serial port on the board other than the USB port but I'm using that for the Bigtreetech tft35 v2 display so that is not an option for connecting OctoPrint to the board.

There are 5 inputs on the board for stepper drives and the TMC2208 stepper drivers that I have installed operate over UART so I'm not opposed to using the extra stepper driver port on the board to communicate with the Pi if that is an option, but figuring out how to use the Z min plus the Z max pins to connect the Pi would be ideal.

## board graphic pins

• Indeed, MKS boards are based on RAMPS (so "pins_RAMPS.h" are edited on video) and AVR-based. SKR is ARM-based (LPC1768), and use different pin symbols. (The voltage difference agains Pi is the same, though.) The video (@2:40s) presents how to free pins D18 (TX1) and D19 (RX1) and enable communication over this by setting #define SERIAL_PORT 1. But do you know how to resolve the question of @ipatch? I could only find instructions for connecting to SKR via TFT. If any pins could be successfully configured for OctoPrint connection? – octopus8 Feb 3 at 5:50