The parallel DPI display interface is by far the most common connection supplied by embedded processors. Even in cases where there is an external Display Controller using a Controller Interface which is not DPI, there is often a DPI connection to the display itself. This paper will explore methods to test and debug a DPI interface. The primary methodology used for display test and debug is to create a specific pattern on the display. We will first define several important patterns, and then demonstrate how to apply these patterns to effectively test displays and debug issues which arise. All of the patterns and functions are standard components of the Kozio kDiagnostics environment.