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Building Your Own Digital Device?

Posted by Cliff on from the starting-from-the-ground-and-building-up dept.

Skaven04 asks: "After finishing up my Digital Design class this semester I've suddenly got the urge to build something really cool. I'm leaning toward a processor/pda/calculator thingamajig. Not really a processor, considering that it wouldn't be following any set standards, like x86, but basically a machine that I can program with my own assembly language, have keyboard input, and (most likely) an LCD output (like on your TI85 or whatever). What I'm seeing in my head right now is an 8-bit design with an ALU (like the 74LS181) as the centerpiece and naturally a few 64K RAMs and various registers, counters, etc. as necessary to implement my command set. Has anybody else out there ever undertaken this kind of project? What are some sites I could visit to get a good outline of the best way to approach it? What are some good places to get the parts cheap? Any suggestions on displays? Links to similar projects?"

3 of 35 comments (clear)

  1. work by dstanfor · · Score: 3, Interesting
    While this sounds cool, it would end up being a ton of work. However, you can do some searches at slashdot or google for free VHDL cores and you'll find some pretty interesting things. I'm assuming you'd like to program an FPGA instead of an ASIC and instead of using an off the shelf processor so this would be the place to start.


    Probably a better option, though, will be to continue taking design courses. look into a computer architecture course. In mine, we made a non-pipelined CPU in VHDL. Also look into what you may do for your senior design course. This is where you'll get free reign over a lab and a budget from school.

  2. Spec it out by m_evanchik · · Score: 4, Insightful

    For any project, the most important aspect is to have some clear objective.

    A cool digital thingamajiggy just doesn't cut it. I'd say your first step is to get ideas for a purpose for your thingamajiggy first. Ask your fellow students and professors what they would like but can't find already made.

    Once you have a purpose specced out, you can make a design to match that purpose. Even just making one modification to a design type can be cool. Like a calculator with a cool-looking or durable form factor (great excuse to play around with a plastic mold-maker), or unique input or output options.

    Ultimately you should think about your end user and what will serve him or her best for some list of tasks. Design for the nontechnical humans.

    I know I'm giving just added questions rather than options, but you will find when you get out of the classroom that in the best designs form follows function. Figure out the function and then design around that.

    --

    evanchik.net

  3. Re:Have fun! by stienman · · Score: 3, Informative

    You can get that LCD from jameco, 128x64 Graphics LCD

    The current ratings on the web site are wrong, check out the data sheet first. Very low power.

    As far as designing your own chip, the only suggestion I'd have is to pay very careful attention to power consumption which is (relatively) very high for nearly every configurable chip you can get. You may end up looking towards CPLDs.

    -Adam