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2 - Layers Upon Layers
The functions to access the ebm's display are organized into three layers, with the tradeoffs of complexity and flexibility. The display buffer is organized as an array of bytes; at four bits or 16 colors per pixel, each byte contains two pixel entries, for a total of about 24k for the entire screen. This buffer is used to communicate between a user program and the Operating System, which handles the data transfer to the LCD display.Interacting with that plane of data is the responsibility of the LCD_ functions (found at /franklin/SDK/sneak32/include/lcd.h):
| LCD_DisplayInit() | LCD_DisplayClose() | LCD_GetBuffer() | ||
| LCD_DisplayClear() | LCD_SetLogicalOrientation() | LCD_GetLogicalOrientation() | ||
| LCD_DisplayUpdate() | LCD_QueryHeight() | LCD_QueryWidth() | ||
| LCD_QueryDepth() |
At this level, the responsibility for graphics is entirely in the developer's hands. You will need to make calls to initialize and close down, get the bit plane depth, the screen orientation and size, as well as handling clipping, updating, and so forth. An example of programming at this low level is shown in the Jogwheel application, available on the ebm website.
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