Update your 3D printer firmware without a bootloader! - YouTube
DIY RepRap 3D Printer for Beginners - Part 3: Code
ESP32 3D Printer Motherboard, 520Kb RAM USB Update Firmware 240MHz Clock Frequency 3D Printer Control Board With Limit Switch For Serial Screen - Walmart.com
Megatronics 2.0 - RepRap
How to Make a Big 3D Printer at Home Using Arduino - Hackster.io