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Author Topic: z80-like portable computer for <$30! (If you build one)  (Read 63273 times)

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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #75 on: August 17, 2013, 01:59:38 pm »
Well you could already build it. There is just no software for it yet :P
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Offline aeTIos

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #76 on: August 17, 2013, 02:04:16 pm »
ah lol... so there are no changes in the part list and such.
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #77 on: August 17, 2013, 02:07:54 pm »
Yes there have been quite a lot of changes
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Offline willrandship

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #78 on: August 17, 2013, 07:22:30 pm »
The only really solid things about the project currently are:

ez8 micro: get a 64xx series one, please. The 082A series is smaller, but has an internal oscillator. However, the difference in flash causes several problems for programming for cross-compatibility.

speaker: Get one. It will probably be hooked to the propeller, but that could change.

SD card: See speaker. Same reasoning.

Keyboard: Get a PS/2 female port unless you want to chop off a plug.

Other than that, it's hard to guarantee anything. Most of the other circuitry won't affect compatibility, as long as it works. Video is a difficult question, since LCDs cost a lot of money (read: >$15 for anything good) and the propeller supports VGA and Composite out of the box. Right now, we're thinking VGA, with various text and graphics modes the propeller will handle.

For example, text mode with customizable fonts would make for an easy monochrome tile system, and there will probably also be a color tile system. There will definitely not be a direct 24-bit color bitmap mode, since that would take 230 KB just for a 320x240 resolution, and the propeller chip only has 32 K total. Text modes can be much higher resolution, though, as can certain drawing-based methods, if someone codes them ;)

The method for interfacing the ez8 to the propeller is still being discussed. The ideal, in my opinion, would be a shared RAM area. By using an SPI RAM chip (32k or so) or perhaps by making the propeller's 32k RAM space available over SPI, the graphics could be implemented in a framebuffer, and other devices could be handled simply by writing the correct byte.
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #79 on: August 19, 2013, 09:36:45 am »
Propeller chip running a demo program of it receiving and processing bytes from the eZ8 at 115200 baud. Haven't tested it at a higher rate yet. Video generation and serial is handled by cogs running ASM code. The processing of data is done by an interpreter, so that is a little bit slow. I have to put delay in between writes because of this. When I switch to all ASM that should not be a problem anymore.

Edit:This is composite video by the way.
« Last Edit: August 19, 2013, 09:38:54 am by Keoni29 »
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Offline TIfanx1999

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #80 on: August 19, 2013, 04:46:42 pm »
Very nice! :D
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #81 on: August 19, 2013, 04:54:12 pm »
Thanks. I am gonna search for a nice graphics engine to use. I learned the Spin interpreted language used by the propeller by looking at the library code. I am far from being able to write propeller ASM (short: PASM), but I think using someone elses graphics engine would do just fine.
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #82 on: August 20, 2013, 05:23:09 am »
Oh, I have not showed it here, but I was working on a wooden enclosure for the thing.

I posted it on my blog, but I was not sure if I put if on omni yet.
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #83 on: August 23, 2013, 10:31:04 am »
I am working on a new graphics engine for the propeller chip. This engine has 16 colors per tile instead of 4. It might even become 16 colors per 16x1 pixels, but I'm not sure yet. Tomorrow I will work on smooth scrolling and maybe sprites.

Edit: Forgot to attach the captured picture. This composite video comes from the propeller chip and is captured using a pci video capture device.
I blend two tiles together by alternating them rapidly to achieve this effect. One of the tiles has horizontal color bars and the other has vertical grayscale bars. You could blend together any color you like. I still have about 130 unused cycles in between tile processing and outputting pixel data, so I have some cyles left for sprites.
« Last Edit: August 23, 2013, 01:18:00 pm by Keoni29 »
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Offline aeTIos

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #84 on: August 23, 2013, 02:30:59 pm »
Problem: I think you need a monitor for this which I don't have D:
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Offline DJ Omnimaga

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Re: Re: z80-like portable computer for <$30! (If you build one)
« Reply #85 on: August 23, 2013, 05:33:10 pm »
Very nice Keoni :D.
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #86 on: August 23, 2013, 06:19:35 pm »
Quote from: aeTIos on August 23, 2013, 02:30:59 pm
Problem: I think you need a monitor for this which I don't have D:
It will work on any ntsc compatible television with composite video input. (pal looks like crap, but it is possible)
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Offline aeTIos

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #87 on: August 24, 2013, 03:31:21 am »
Hmm.. I see.  Still doesn't get me a TV lol.
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #88 on: August 24, 2013, 05:00:47 am »
You know what's crazy? A second hand crt television is a lot cheaper than a monochrome lcd. It also has the added benefit of being a color display and it has a larger resolution than those cheap 128*64 lcd displays.
« Last Edit: August 24, 2013, 05:01:16 am by Keoni29 »
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Offline DJ Omnimaga

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Re: Re: z80-like portable computer for <$30! (If you build one)
« Reply #89 on: August 24, 2013, 11:53:56 am »
Is that why the TI-89 and Classpad 330 still cost $160? :P
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