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Michael Karas
09/14/12 09:10
Read: 530 times
Beaverton Or
USA


 
#188326 - Graphics Displays
Responding to: ???'s previous message
Welcome to the world of graphics displays. When you want to modify one pixel out of a field of other pixels it is necessary to read the other field data, mask it to keep the other data and insert the new data that you want. Then finally you write the new data back.

In your case where the field is a byte of 8-pixels you pre-read the byte. Then either OR in your new pixel if you want to set the new pixel or you would AND the byte with the NOT of your pixel mask to clear the pixel. Then write the final value back to the display.

Some displays, particularly those that use a serial interface, cannot be read back to get the previously written pixel values. For this case you need to keep a local buffer that keeps a pixel image of the display available for you to reference. I have posted some sample ideas of how this is done with a buffer like this at the following link. You will find the buffer concept particularly valuable when you come to write font glyphs to the display. Do all the work in the buffer first and then use fast loops to copy the appropriate rasters of pixels from the buffer to the display.

Even if you have a display that supports read back of the pixel image you will generally find that operating the display in read/write mode for each pixel is painfully slow.

http://www.carousel-design.com/GraphLCD.html

Michael Karas


List of 28 messages in thread
TopicAuthorDate
Nokia 3310 display [PCD8544] dot problem      Samarth Godara      09/14/12 08:02      
   NOTE-      Samarth Godara      09/14/12 08:32      
      Graphics Displays      Michael Karas      09/14/12 09:10      
         memory management      Samarth Godara      09/14/12 09:31      
            it would not      Erik Malund      09/14/12 09:50      
               more help      Samarth Godara      09/14/12 10:30      
                  Search engines?      Per Westermark      09/14/12 12:20      
                     confused      Samarth Godara      09/14/12 13:13      
                        No exact answer      Per Westermark      09/14/12 13:36      
                        Type of Thinking      Michael Karas      09/14/12 14:34      
                           I second that      Erik Malund      09/15/12 08:05      
                              doubt - interfacing memory with 8051      Samarth Godara      09/15/12 11:52      
                                 Why would you want to      Hal Albach      09/15/12 16:58      
                                    Don't overlook the "extras"      Richard Erlacher      09/15/12 20:29      
                                    why to use my own design      Samarth Godara      09/15/12 20:47      
                                       which is corect, but      Erik Malund      09/16/12 06:44      
                                       Wrong approach for India        Kalpak Dabir      09/16/12 06:50      
                                          my approach + new doubt [start execution]      Samarth Godara      09/16/12 09:06      
                                             Perhaps you've overlooked some options      Richard Erlacher      09/16/12 12:44      
                                                my circuiting & a Really surprising, Good Board      Samarth Godara      09/16/12 23:00      
                                                   Not all 805x variants are the same       Richard Erlacher      09/17/12 01:54      
                                                   Besides 8051 there are other....      Kalpak Dabir      09/17/12 02:00      
                                                   BEWARE      Erik Malund      09/17/12 07:38      
                                                      Shortest path      Per Westermark      09/17/12 09:05      
                                                   use direct wiring when using point-to-point      Richard Erlacher      09/17/12 09:30      
                                 Are you determined to fail?      Erik Malund      09/15/12 19:41      
                           SiLabs isn't the only possible solution      Richard Erlacher      09/15/12 20:22      
                        Have you considered the datasheet(s) and 8052.com's search?      Richard Erlacher      09/15/12 20:17      

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