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Author Topic: z80-like portable computer for <$30! (If you build one)  (Read 60956 times)

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Offline willrandship

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #45 on: June 27, 2013, 10:15:24 pm »
Alexis, this is a project I'm building. I only just got the parts, so there's not much to look at for the moment. :P
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #46 on: June 28, 2013, 04:10:33 am »
I am pro-vga output or at least composite out. Could you make an expansion port on it so you can hook up one of these vga boards?
http://www.microvga.com/
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Offline willrandship

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #47 on: June 28, 2013, 01:31:25 pm »
There will, at the very least, be a pin header. 0.1" spacing, so it should be easy enough to attach to.
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #48 on: June 28, 2013, 02:40:16 pm »
That's good to hear. A lot of SPI devices can be connected to a 3,3v expansion port, so that's great.
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Offline zigzagjoe

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #49 on: June 28, 2013, 04:56:36 pm »
Was bored, so finished hashing out the ARM-based idea. Click here for google doc with block diagram, pin assignments and parts manifest.

Too bad this is the only DIP ARM chip out there; it's a bit IO constrained, though you could free up to 3 GPIO pins along with 8 bit data bus and SPI, at the cost of piezo speaker and PC link. One more GPIO if the reset switch is deemed unnecessary... could just use a momentary-off switch on Vpp for the same effect, i suppose?

An interesting idea I had is that from whatever interpreted language, an ARM routine could be loaded into RAM and run from RAM to effect an increase in speed in crucial areas. Kind of want to build it... would be fun to write the core code.
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Offline willrandship

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #50 on: June 28, 2013, 05:52:34 pm »
Well, with an ARM chip you might as well just load something like eLua onto the chip.

Would anyone be terribly offended if I dedicated all the analog input option pins to other things? It's the only port on the chip that doesn't have other stuff I want to use for its own purpose (like UART and SPI)

You could still have analog input through the coprocessor chip, though. It wouldn't be as fast, and would be bottle-necked by audio processes, but it would be available if anyone DID need it.
« Last Edit: June 28, 2013, 05:53:30 pm by willrandship »
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Offline Spyro543

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #51 on: June 28, 2013, 06:08:15 pm »
What exactly would it be needed for? I can't think of anything besides some kind of weird expansion bay...
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #52 on: June 28, 2013, 06:52:27 pm »
A mic? Not sure if it has enough ram to do anything with analog signal processing.


@zigzagjoe really nice and cheap. The ram would be kind of a problem though. Aren't there cpu in that series with more ram?
« Last Edit: June 28, 2013, 06:58:06 pm by Keoni29 »
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Offline zigzagjoe

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #53 on: June 28, 2013, 07:42:14 pm »
Quote from: Keoni29 on June 28, 2013, 06:52:27 pm
A mic? Not sure if it has enough ram to do anything with analog signal processing.


@zigzagjoe really nice and cheap. The ram would be kind of a problem though. Aren't there cpu in that series with more ram?

Yeah, you can get ones with more RAM and ROM, but only in surface mount packages. That's one of two ARM chips in a DIP form factor available, so went with it in in the spirit of a hobbyist-friendly design. Other one is an 8-pin relative with even fewer resources, definitely not going to cut it.

If you throw DIP out the window, though, there's a lot of options - USB client, as much RAM/ROM as you could want, and more powerful Cortex-M3/M4 cores, to name a few. Possibly even a display interface, though that would increase complexity quite a bit.

Truthfully, it probably makes the most sense to just get a board made anyways, seeing as there are very few graphical LCD modules with through-hole-friendly layouts. FPC connectors, which you'd use for the display proposed by the OP, are all SMD. That color LCD is a hair better in that it has solder pads that you could conceivably solder wires to, but it's meant to be soldered to a board.

It'd also allow you to integrate a keyboard matrix for a semi-handheld product. As long as you don't go whole hog with BGA chips, SMD can be done at home without *too much* effort via a heat gun or toaster oven. Have even heard of people doing it purely by hand.

I think it could be a fun project anyways, working with the limited resources of the LPC1114. You would want most code to be interpreted code, with just the lowest level routines stored in ROM. Bootloader, input, low-level comms (rs232 or usb), display routines, storage routines, floating-point emulation, interpreter (obviously), and a basic monitor program. All the stuff that needs to be fast. Still, going to have a look to see what $3 gets you in a SMD ARM chip.

Re: eLua. Not enough RAM/ROM to manage it. You'd want as minimalistic a language as possible, if using the LPC1114. Fancier [SMD] ARM chips would have enough RAM that you could set things up that entire user binaries could be copied to a specific offset in RAM and execute them from there.
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #54 on: June 29, 2013, 03:01:41 am »
Soldering components to smd isn't that bad, but soldering wires instead of using a ribbon cable will give you a bad time. I once had bridge an entire ribbon cable with 22 traces in a psone lcd screen using wires. In the end it worked though, but it took me about two hours. Afterwards the lcd started glitching and there was smoke and then I blacked out.
« Last Edit: June 29, 2013, 04:24:10 pm by Keoni29 »
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Offline willrandship

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #55 on: July 03, 2013, 05:54:06 pm »
That's why I ordered a breakout board for the LCD. :P If I start making lots, I'm definitely going to put in a standard connector on the board.
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #56 on: July 20, 2013, 01:30:43 pm »
I had a look at the IDE and especially the blink LED example that came with it. I understand that most of the code is for setting up the microcontroller and not for the cpu itself, but it's a lot of code right there. Have you seen it? Do you know if there is a community that uses these mcu, because I am sure I won't be able to figure out everything myself.
« Last Edit: July 20, 2013, 01:31:22 pm by Keoni29 »
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Offline Keoni29

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #57 on: July 23, 2013, 06:12:58 pm »
*Minor bump*
http://8times8.host56.com/ez8tut.html
I am working on this tutorial as I'm learning how to program for the device. I thought that would be the best way to keep everyone updated about it.
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Offline DJ Omnimaga

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #58 on: July 23, 2013, 09:51:19 pm »
That is cool to hear :)
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Offline Sorunome

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Re: z80-like portable computer for <$30! (If you build one)
« Reply #59 on: July 24, 2013, 05:09:12 am »
yay, that's cool!
* Sorunome expects awesome stuff :P
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