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Forum Index : Microcontroller and PC projects : Maximite 2.3 minor bug
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5012 |
This is a copy of a email I sent to Geoff and his reply. It looks like there is a minor video glitch in the 2.3 update. Hi Geoff I may have found a little video problem with the 2.3 update. After the update I noticed the display ( VGA out ) seamed noisy, like a bad cap in the power supply sort of interference. I thought it was the monitor, so changed that, no change, then tried USB power instead of the ext power, still no change. I then changed the firmware back to 2.2, and it cleared up. I reloaded 2.3 and the problem was back, then changed again to 2.2 to confirm, clean. Where there any changes to the way the video is generated? Its like digital noise is getting into the VGA, or the video ram space is been written while its been read. If your aware of the problem, cool, but if not I'll do some more tests to confirm the results. I could take a few CRO screen shots of the VGA signal, with say a vertical line on the screen, and send them to you, running 2.2 and 2.3 Glenn Damn, this is a problem. When developing the firmware I noticed the noise. It is caused by the normal video signal being delayed by by 8 bits which in turn is caused by the SPI interface being triggered a little late in respect to the horizontal sync. It is intermittent (ie, only on random spots in the video stream) and I never figured out the exact cause but it seemed to be worst when there was heavy traffic on the PIC32 switching matrix (this matrixes the flash, ram and peripherals into a common address space). Could also be associated by misses on the instruction cache. Anyway, I was able to minimise it by varying the level of optimisation made by the compiler and ended up with optimisation level 1 as the best compromise. It seems that something (I don't know what) in ver 2.3 has upset this delicate balance. The real problem is that I don't have a VGA screen with me - I have the full development environment on a notebook, a Maximite and a keyboard - but no VGA monitor. I will have a think about it but I can see myself buying a VGA screen in Darwin (we reach there in 4 days) and having another go at nailing it. The only issue is that I will have to lug the screen around Australia for 8,000Km before we get back home. So, give me a few days to think on it and hopefully find an answer. BTW This would make a good item for your forum. Feel free to copy your question and my answer to the forum if you wish. Geoff The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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