Survey of Video Generation Possibilities

[Garth]

Are you looking to bring the frame rate up or is 8 frames a second all you would need for your purposes?

My purposes may never need more than eight, but as stated in another topic, I am in the process of slowly building a new workbench computer which will be able to do it several times as fast even with the same software. I don't often have any need at all for graphics, but now the basics are developed for the next time I do. One of the next steps, assuming I take it further, would be to make it only update the portion that's new, rather than refreshing the whole screen. Then if I had something like a cursor to move around, it would go much, much faster. The smallest set of dots you can update is a vertical stack of eight dots; so then if you had a cursor of, say, 8 dots tall and six wide, you'd need to update six bytes minimum, but usually 12 bytes since the cursor would usually be straddling a byte boundary.

Let's see if this graphic works out. It represents a portion that's two bytes high and six bytes wide:

Code: Select all

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╞═╬═╬═╬═╬═╬═╡
├─╫─╫─╫─╫─╫─┤
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└─╨─╨─╨─╨─╨─┘

[/size]
The 64x128 LCD is a bit small for text, but the fact that it goes in groups of eight dot rows works out well for updating portions of text, particularly if you can confine the text to sets of 8 dot rows, and don't have to straddle rows. Of course if you wanted a font that was 15 dots high plus a few dots' separation between rows, you'd have a bigger software job.

[brad]

Does the LCD driver chipset allow you to update specific sections of a screen at a time? I haven't had much experience with these ones but I thought you just had to send it a full screen worth of data each time.

[Garth]

You can update as little as a byte at a time, and the change shows up immediately. A byte is a vertical stack of 8 dots. A full column on this 64x128, since it's 64 dots, is 8 bytes. This one has no gray scale or color, so each dot is either on or off.

[brad]

That would be fantastic for text I imagine since you would just need to be updating small sections at a time.

[Garth]

I should have added that another function built into the LCD is that it lets you tell it where the top is, meaning that to scroll up or down, you just give it that instruction with the parameter, then send only the new data you need to put at the top or bottom, instead of re-sending the whole screen.

[Garth]

I just came across this page that shows a lot of small fonts that people have figured out for LCDs (or any other video), to get as much text of different kinds as will fit readably in whatever size of LCD you have:
http://www.hpcalc.org/hp49/utils/fonts/
The picture at the right end of each post has the thumbnail. To get a bigger picture, click on "(Details)" next to the name of the font, then scroll down. There are different ones for sizes, Greek characters we use all the time in engineering and math, math symbols, etc.. I've figured out things like this before, and it took quite a bit of time to try different ideas to make them as readable as possible, especially for the tiniest font where you have to get a bit creative to get the characters in the fewest pixels and still have them come out readable. Here that part is already done.

[brad]

I have made different fonts for LED screens before and I know what you mean about trying to get readable characters in the fewest pixels possible. I found you can get alot of characters in a 3x4 pixel grid however there are some that just don't work correctly like M and W