In some circumstances, a firmware flash may fail half way, which will cause the motherboard to “lose” its bootloader. The bootloader is a part of the firmware that allows the motherboard to be upgraded over USB. Without the bootloader, the firmware must be flashed using the ICSP programming port.
The bootloader can be reinstalled using either a USB programmer device, or using an arduino device.
The simplest process.
Don't have a USB programmer lying around? Feeling like you would like to buy an arduino for future projects anyway? Read on…
You can use an Arduino as a USB programmer fairly easily!
Download and flash this awesome arduino bootloader flasher by Nick Gammon.
All your pins on the MKS Gen L should be connected to the ICSP port (see first image below).
Don't have a USB programmer lying around? Feeling like you would like to buy an arduino for future projects anyway? Read on…
You can use an Arduino as a USB programmer fairly easily!
Please read this article first for the main guide. We need to do three things:
For step 1, you need to flash the programming sketch to the arduino. See “Load the sketch” at the link above.
For step 2, you need to wire up the device. See the link above if you have an arduino uno, or nano. If you have an arduino MEGA, the pins are different - use the wiring here]
You may have to connect a jumper from ground to reset on the arduino, to prevent it being reset during flashing.
for step 3, make sure to cross your fingers and toes.
Once you have flashed the bootloader, you can flash the firmware using your usb cable directly to the printer. Don't forget to follow all the instructions!