General purpose board using Arduino MEGA PCB template, with Arduino Nano controller board, LCD+Keyboard, DS3231 RTC, NRF24L01 radio, and DS18b20 temperature sensor - Share Project - PCBWay
Arduino Shields - SparkFun Learn
Arduino Shields Are Ready-Made Addons for Circuit Development
Ardunio UNO R3 Template - Connecting to 3.3 and 5 volt Pins - Schematic - KiCad.info Forums
How to Design a Custom Arduino Shield Board | Blog | CircuitMaker