Do You think HD44780 based display can display more than 8 user-defined characters? No... Is it possible? The virtual memory was displayed as 16 character patterns. In this way the full line of the x * 16 alpha-numeric display were exchanged into bitmap, having copy in the memory of  the microprocessor. It gives us a possibility of modification the pattern by all accessible instructions of the micro-controller…

The effect was reached with the alphanumeric HD44780-Based display in 4-bite mode and depends on rotary projection of two various contents of the user-defined character patterns in CGRAM. This areas can be used as general data RAM. The deterioration of the quality displayed chars is practically imperceptible. However, it depends of the contrast setting. Graphic is displayed on the principle of the usual subroutine, and  the display is ready for the normal work after that.

The example project and source code is in the download.