display

I've got an on-going project to build a battery powered device. I want to be able to run the whole thing at 3.3V so I can easily and efficiently run it off a single LiPo cell. I also want to use a simple monochrome, graphical LCD for this project, but I couldn't find one that would run off 3.3V. For various other reasons, the project requires that the LCD is a classic 8bit parallel module as I had run out of hardware serial ports and bit-banged was making the refresh seem really slow. I found a few that would run the control lines off 3.3V but still needed some higher voltage to power the screen or back-light. Eventually I bit the bullet and decided to go with one of these from Farnell because it was the cheapest back-lit 128 by 64 pixel display I could get from them. It is a really good choice as it even includes electronic contrast control, something I was expecting to have to do in external circuitry. However, it isn't a nice 0.1" pitch module, it comes out to a 0.5mm pitch FPC connection.

Sketch update
There have been some changes to the ChipKit libraries since release, some of these changes caused the Pong sketch to stop working. After a helpful bug report from someone trying to build their own I had a look at the source to see if I could fix it. After a bit of investigation I discovered that in the old code using a digitalWrite() after an analogWrite() would leave the PWM timer running in the background. This isn't power efficient, so it's been fixed, however the new code tests to see if any analogWrite() calls on other pins have occurred and if not shuts off Timer 2. Unfortunately this means writing any of the PWM capable pins in my code shuts off Timer 2 as I don't use analogWrite() but set up PWM manually. The solution I came up with was simply to move the enable lines for the two player scores to pins 11 and 12, from 8 and 9 avoiding using any PWM capable pins. My Life demo is unaffected as I didn't use any pins for output other than the VGA pins. Updated schematics and source are included.

Video Graphics Array "VGA" is a standard for computer display. It has a lot going for it in the hobby electronics field as it is a pretty simple standard and quite straight forward to implement with sufficient signalling speed, there are also a lot of monitors around to test projects on! Colour is a lot easier to generate on a VGA monitor than on a composite video monitor, but it requires a lot more speed as the frames are more detailed and there are more signals to generate.