Bootloader recovery - ThomasToka/MarlinFirmware GitHub Wiki

If you should once come in the situation to reflash your bootloader here is the process of the recovery:

• you need a st-link burner (also clones work)
• get the st-link software from the st-link site
• locate the 4 pins of J201 on the board
• from the side of the card reader it is: vcc,dio,clk,gnd
• connect wires to your st-link
• load the bin bootloader into stlink, leave everything else default
• connect to your board under "Target" -> "Connect"
• do under "Target" -> "Erase chip" first
• then click "programm"
• click start, its ready within some microseconds

see the pinout in the user manual: user_manual_ender_s1_pro.pdf

bootloader is here: https://github.com/ThomasToka/MarlinFirmware/blob/Firmware-Binaries/STM32f401RCTx_BootLoader_v1.bin