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Forum Index : Microcontroller and PC projects : PIC32 with graphics library
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MicroBlocks Guru  Joined: 12/05/2012 Location: ThailandPosts: 2209 |
This could make a Maximite color version even better/ maybe easier. Details here: http://www.microchip.com/pagehandler/en-us/technology/graphi cs/products/pic32lccg.html This uses the integrated PMP instead of a SPI line per bit colordepth. If i understand it correctly by using the PMP you can output the data parallel. This should open the way for a flexible use of color depth, depending how much RAM is reserved for a frame. With lower resolutions even double buffering should be possible. When a external ram is used even higher resolutions with higher color depth is possible, although that would require extra chips and drive up the costs. Edit: I studied it a little bit and from what i have read in the references of the PIC32 it should be possible to use DMA to output a chunk of memory to the Parallel port. I am not sure if it is easy to select how many bits, but 8 bits color would be a good way to test it. Make a resistor ADC for those 8 bits in RRRGGGBB and you have 256 color. Microblocks. Build with logic. |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3801 |
More RAM needed than the PIC32 has, so yes external RAM. John |
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darthmite Senior Member  Joined: 20/11/2011 Location: FrancePosts: 240 |
The LCC card have a 512k x 16bits 10nS SRAM for support of the higher resolutions. Actually is only for LCD/TFT but i think with a R2R DAC for each colours and a level converter for go directly in a VGA monitor it can be doable. For 16bits colours they use a RGB 565 standard format , you have the HSync and VSync directly accessible on the board too. Darth. Theory is when we know everything but nothing work ... Practice is when everything work but no one know why ;) |
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| MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
?? The point i tried to make is that by using the parallel port to generate VGA you would not need 3 SPI devices and 3 DMA channels. I never used the DMA so i am not able to be sure what i suggest is possible. Another point is that it can be made with only internal memory but when needed can be extended with external memory, making future expansion possible. I can imagine designing the pcb with a placeholder for the extra ram. It would provide the user a VGA upgrade path without the need for an extra pcb board. The memory requirements would not be any different as the current method, it would just make 1 to 16 bits color depth possible instead of 1-3 bits. Microblocks. Build with logic. |
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| darthmite Senior Member Joined: 20/11/2011 Location: FrancePosts: 240 |
Ha oki i see your point 
My point was to have a system who can handle more resolution and colours. Just with one DMA and PMP , no SPI at all are used. For internal memory solution it's allot more easy and cost less to build. Actually i made a card with external SRAM + R2R DAC and level converter to be able to put it on a VGA screen. But ... i made some mistake in the conception and now i wait up i get the new PCB , then it will be again the hell to solder all little smd components 
Here is a photo from the actual design. 
After checking if the new design is OK i have to understand correctly how the DMA / PMP work with the SRAM and video generation ... And for this , the microchip examples are not really helping me 
Cheers. Theory is when we know everything but nothing work ... Practice is when everything work but no one know why ;) |
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| MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
Yeah, the microchip samples are not clear at all. I searched the internetz for a long time and the only workable version of this was here: http://www.wix.com/picdevelopersteven/index#!__projects/vga- display Maybe he would like to share. Microblocks. Build with logic. |
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| darthmite Senior Member Joined: 20/11/2011 Location: FrancePosts: 240 |
Will be good to have the source code from this one as example
Theory is when we know everything but nothing work ... Practice is when everything work but no one know why ;) |
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