Here are some key features and details about the 2004 LCD Display RepRapDiscount Smart Controller with Adapter:

LCD Screen: The "2004" in the name refers to the 20x4 character LCD screen. It has four lines of 20 characters each, providing enough space to display relevant information about the 3D printing process, such as temperature, progress, and printer status.

Control Knob: The controller typically includes a rotary knob for navigating through menus and options on the LCD screen. Users can turn the knob to scroll through the menus and press it to select options.

Adapter: The "with Adapter" part of the name likely refers to the fact that the RepRapDiscount Smart Controller often comes with an adapter board or a set of connectors to make it compatible with various 3D printer controller boards. This makes it relatively easy to integrate with different printer configurations.

SD Card Slot: Many versions of this controller also have an SD card slot, which allows users to load 3D print files onto an SD card and print directly from it. This can be very convenient as it eliminates the need to connect the 3D printer to a computer during printing.

Compatibility: The RepRapDiscount Smart Controller is compatible with various 3D printer firmware, such as Marlin and Repetier, and can be used with 3D printers based on the RepRap design principles.

User Interface: It provides an intuitive user interface for controlling basic printer functions, including preheating, homing, and starting/stopping prints.

DIY Community: This controller was popular in the RepRap and DIY 3D printing communities due to its affordability and ease of use.