Hi Garry2005,
You have asked a lot of questions so I'll try my best to answer them for you.
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Originally Posted by Garry2005
I don't even know which one (or ones) would be best suited for this,
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The choice depends on how many I/Os you would need. The "bigger" the PIC, the more I/O pins they have.
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Originally Posted by Garry2005
how they intrerface to the PC (or keyboard controller),
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See image at bottom of this posting. You connect pins of the PIC to the PC PS2 keyboard socket, if the PIC mimic the keyboard correctly using software, the PC won't know it is not talking to a keyboard.
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Originally Posted by Garry2005
how many inputs the various ones have, how many PIC's I'd need...would I need several for this project?
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We don't know. You would know how many I/Os needed so we asked the question earlier of how many switches and LEDs you required.
Incidentally, the same question has been asked three times already. First by Jay, then myself and lastly by WilliB. You need to think about it and give an answer. Not a 100% exact one but a ballpark figure with some reserves would be nice.
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Originally Posted by Garry2005
If so, do they connect in parallel somehow?.
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Yes, sort of but using different methods.
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Originally Posted by Garry2005
Do the inputs employ key-bounce protection? What about the business where I'll have certain toggle switches that go on and stay on?
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No problem, software can debounce the switch. With software, a momentary switch can also look like a toggle sw too.
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Originally Posted by Garry2005
Do the switches provide Vcc to the PIC, or ground, or is it a simple switch closure?
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Can be either, depends on how you wrote the software. You can even have the switches in matrix connections to simplify PIC connections and have a lot of switches.
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Originally Posted by Garry2005
How do PIC's work, basically:
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It has CPU, timers, I/O ports, ROM and RAM and oscillator, maybe more depends on different PICs. So its like a miniature computer already. Someof the PICs are one-time proprammable and others can be reprogrammed many times as they use EEPROM/FLASH to store the program codes.
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Originally Posted by Garry2005
Is there a PC-resident development program where you create the PIC program
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Yes, from Microchip the manufacturer, free of charge.
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Originally Posted by Garry2005
and download it to the PIC?
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You'll need a hardware programmer to do that. Ranging from simple several components serial design to designs that sits between PIC and a parallel printer port. There are dozens of design on the web which can be easily built. Ready built one are available for sale which comes with the associate software to handle the programmer. Web hardware designs often work with the free & excellent software like the one by our forum moderator Nigel Goodwin.
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Originally Posted by Garry2005
Which leaves me asking: Does the chip have memory for the program, or does a PIC require seperate memory?
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It doesn't need extra memory in most cases. The PIC has very efficient(RISC) code structure, most of the time the program would fit into its internal memory and you have many choices on the memory size within the same series of PIC. This is also the big incentive to use a PIC in the first place. If one has a program that needs 64K or more, then maybe there are other choices.
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Originally Posted by Garry2005
Would I get just a PIC chip and build around it, or is it a board with all the necessary stuff to make it work?
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As an DIP chip, with 18-pins, 28-pins or 40-pins or in other form of packaging.
25th June 2005, 06:15 AM
Linear Mode
