How to Install Klipper on Creality Ender 3 S1: Config and Setup

Hey there. I have the S1 Pro with the F1 chip (yes, I checked, early printer) and I have issues with the setup. What I have done:

  • Compiled the firmware for the printer using the S1 normal setup, STM32F103, 28KB, USART1 PA10/PA9.
  • Put it on the root of a recently formatted SD card, I’ve tried all sort of different filenames due to marlin’s pickiness with filenames, but I tried firmware.bin and others.
  • Updated the firmware and something to updated as the screen is black with some dots on after boot.
  • I use the official printer.cfg for the S1/S1 Pro from the klipper github.

I just get:

mcu ‘mcu’: Unable to connect
Once the underlying issue is corrected, use the
“FIRMWARE_RESTART” command to reset the firmware, reload the
config, and restart the host software.
Error configuring printer

What did I miss?