Multi-Function Module

Discussion in 'The Projects Forum' started by T.Jackson, Nov 24, 2011.

  1. T.Jackson

    Thread Starter New Member

    Nov 22, 2011
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    Recently I have been thinking about pushing one of microchip's very cheap microcontrollers to the extremes through using a lot of IO multiplexing without the aid of discrete logic ICs. I am at the stage where the schematic is done, and I have built a working prototype a long with some software.

    [​IMG]

    Problem for me is that, I don't know what would be the best features to implement / compromise on. I only have 2KB of program space and I am using C to write the software.

    What I initially had in mind was:

    • Manual general purpose up / down counter (see how many times the door of a shop opens each day to evalute business)
    • Programmable automatic count up / down timer with 1mS resolution (switch on something when the count reaches zero)
    • Lap timer / stopwatch ...
    Here is the schematic:

    [​IMG]

    Can anyone think of some other / better features to implement?
     
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  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    That's about the limit for a 16F62x since you don't have ADC, though you could use the comparator for something.

    For a PIC with everything, including kitchen sink, internal temp sensor, 12 ADC channels and DAC, look at the PIC16F1827, it also has M-Touch capacitive input, 5 timers, 2 SPI/i2C, UART, ECCP & 2 CCP, if you can figure out a way to use all of those with the 16 I/O ports, I'd be impressed.

    Also, I normally put the 100nF/0.1uF cap between Vdd and Vss on the bottom of the board or as an SMD under the IC if using a DIP. Shortest direct path.

    You could free up a bunch of pins by charlieplexing your 7 Segment readout, and adding a 1 wire serial LCD as well.
     
  3. T.Jackson

    Thread Starter New Member

    Nov 22, 2011
    328
    14
    Tri-state octal buffers is what first springs to mind. 74HC245 etc ..

    Good idea. Sometimes I use a 100nF bypass cap for each IC that I have. Bit overboard, but textbook though.

    I used to do a lot of video arcade game board repairs, and I note that it is mandatory that the Z80 CPU is well decoupled. Otherwise it does all sorts of strange things. Resets itself even.

    The Z80 CPU (not microcontroller) -- has 14-pins for an address bus and 8 for data bus. I have seen 200+ chips being under the control of this CPU.

    You can use the same schema for a pic. These 3-cent discrete logic ICs are still relevant.

    I can use 20 x 74HC245 + 20 x 74HC373 + 4 x CD4028 ICs to give an old PIC16F628a 160 I/Os.

    Yes that's right 160 inputs and outputs.

    Go and pick up a 30-year-old textbook and you will see how it is done.

    You there boss?

    Think there would be any interest in a ridiculoulsy large 1024 IO project that plugs into a computer?

    I mean, you could control / monitor a large hotel with that.

    Large, but works out being much cheaper than serially addressing many MCUs.
     
    Last edited by a moderator: Nov 24, 2011
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    Impressive. Just remember this is not a live chat though, and in the USA it is Thanks Giving holiday, a very big deal here. I suspect a lot of folks are going to be out today, visiting with friends and family.
     
  5. T.Jackson

    Thread Starter New Member

    Nov 22, 2011
    328
    14
    If you want more work, then you will allow myself and the team of people that I pick to say whatever whenever.

    Your call.

    No more of this riddle ****. We will speak open and very CLEAR.

    We will usually ask very 'direct questions'

    Bit tired of all the bull if you know what I mean.
     
    Last edited by a moderator: Nov 24, 2011
  6. Wendy

    Moderator

    Mar 24, 2008
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    My call is this site is good the way it is. There is something that attracted you to it.

    Civility, no profanity, and certain subjects will not be allowed (see our TOS). We will keep it friendly. First and formost, this site is a teaching site for all skill levels. You can not learn if you are intimidated or bullied.

    There are many other sites out there that will cater to all tastes. The jobs of the moderators here is to keep it friendly or else. I'm relatively new as a Moderator, but I have had to ban a few folks that just didn't get it.

    If you want to display your work this is a good venue. We get top marks for numbers of hits on the internet. Some folks come once, look around, and leave. Others leave, find that other sites are not as friendly, and come back. Others, like me, came in and made themselves at home. I was thinking of starting a personal blog, but it is free here. I have put a lot of work into my blog.

    There literally is something for all tastes here. We allow free hosting of albums, free blogging, and communication with some of the smartest folks in the industry, people who can appreciate what you do and offer good suggestions to improve on it.

    There are a lot of other people who like it just the way it is. We listen to serious suggestions for improvement, which is what the Feedback and Suggestions forum is about.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Posting multiple replies in a row in your own thread when there are no replies in between is rather poor form. If you have something to add to a thread and there are no replies to your last post, then edit that last post and add what you had to say to that same post.

    You could handle the 7-segment displays by using a couple of 74HC595's and one of the PIC's I/O pins.
     
  8. Yako

    New Member

    Nov 24, 2011
    245
    2
    Arh I think some people have sent Mr Jackson a bit bananas if you know what I mean.

    I don't know this IC, but it is certainly cheap enough @ USD 22 cents a piece. Had a quick look at the datasheet, and I can certainly see a use for it at that price. Traditional tri-state shift register.

    Clock + data lines would equate to using 2-pins on the PIC. Better than using 7. This PIC is good for 5MIPS @20MHz too.

    Could probably handle over clocking a bit too. 24MHz would give it 6MIPS horsepower.

    There's a lot that you can and cannot do with this sort of speed.
     
    Last edited: Nov 24, 2011
  9. SgtWookie

    Expert

    Jul 17, 2007
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