Retromaster’s Electronics Projects

…related to old computers and other assorted stuff…

UFE Video Progress

Posted by retromaster on April 29, 2010

I’ve made some progress with the UFE video output implementation. It works in a very similar way to the TFE+, the circuit is almost the same, except that the driver is a 74lvc244 that operates on 3.3V. It uses the SPI module of the PIC32 to shift pixels out and input capture is used to acquire vertical and horizontal sync. Right now, the video data is loaded manually into the SPI registers but I would like to implement DMA as well. Also, the relatively high rate of the peripheral clock gives me lots of room to adjust the horizontal pixel size, which is a nice bonus.

Unfortunately, it does not work perfectly yet as there is quite a bit of flicker (the photo hides most of it but it is quite visible to the naked eye). It looks like whole lines are shifted horizontally by one pixel on a random basis. At first, I suspected the interrupt timing, but the left limit of the video overlay area (also software controlled) shows a straight line with no flicker, so it looks like it must be a timing issue with the SPI module. I’ll investigate further and improve the situation if I can. It is useable in its current state, but since I was able to obtain good quality video from the 8-bit AVRs, I would expect no less from the far more powerful PIC32.

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