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Re: How to check 125 logic states...?


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yeah, it gives you a really good understanding of whats really happening.

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its the unwise use of it thats the problem, sure.

likewise generalisation vs specialisation.

I often think that
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alas, the former greatly outweigh the latter, yet think they are
programmers.

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the DSP im using now has truckloads of memory, costs US$10, and has 2 x
  12-bit 83ns flash ADCs, with a pair of 8:1 s/h + mux. but that goes
into an exensive box of tricks.

shortly i need to find a *very* cheap micro to run a 300W smps; that
will have far fewer features


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I'm looking forward to trying out this DSPs toolset, as I have quite a
bit of code to write that needs to run very fast. If i choose my data
structures carefully, I shouldnt need to resort to asm at all

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yeah, fair enough. but I think C can be seriously unintelligable
(witness the obfuscating C competition).

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eruditely put.


Cheers
Terry

Re: How to check 125 logic states...?



Noticed this and wondered if it might help - ideas to borrow

http://www.user.dccnet.com/wrigter/picaxe/08M%20IR%20Remote%20with%20127%20keys.htm

David



Re: How to check 125 logic states...?


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http://www.user.dccnet.com/wrigter/picaxe/08M%20IR%20Remote%20with%20127%20keys.htm
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Thanks David
    Unhappily I need to look at the logic states of 125 inputs, not the
open/closed state of only one of a large number of switches. :-(
    My circuit board re-design/expansion's properly under way now. One
thing's for sure, I ain't gunna be able to squeeze 16 x 74HC165 shift
registers into one square inch (25mm^2) of board area as someone suggested!

Cheers
Bob





Re: How to check 125 logic states...?


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http://www.user.dccnet.com/wrigter/picaxe/08M%20IR%20Remote%20with%20127%20keys.htm
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An SO package is about (from memory) 100sq mm (including clearances),
so you might get say 6 of them in your square inch. Then if you use
both sides of the board, you are almost there...
If you build a daughter board like I suggested previously then that
could use up very little practical space on your main board.

Dave :)


Re: How to check 125 logic states...?


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Howdy Dave,
    I think that in amongst all the discussion, most people got the
impression that I'm trying to make a tiny board. Actually the board size
isn't very important, as long as it's not outrageously huge. :-) I just
didn't want to lay out 16 x 74HC165 if there was an easy, practical way
of using a smaller number of other readily-available devices which have
a lot more input pins on each package. But it looks like the original
idea is the way to go after all.
    I'm using ordinary SO16 devices. With all the necessary tracks in
place to connect them to the outside world and using only one side of
the board, I can fit about 4 of them into a square inch of board area.
That will work out reasonably well.
    Thanks to you and everyone for all the suggestions. Some good design
ideas have surfaced from all this. :-)

Regards
Bob




Re: How to check 125 logic states...?


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Get yourself an MSP430 and you'll rediscover the joy, if not the youth :-)

joy in assembly: was: How to check 125 logic states...?



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Nice thought Clifford, and I'm sure you are right, but I think I changed
direction too long ago.

I am one of the people after 25 years with the same company, (TABCorp)
about 7 years ago, I literally told my boss what he could do with his
job. One of the best decisions I have ever made.

I can understand Bob's love of the Zilog family. All of my first micro
projects were all done on a Z80. With undocumented features I discovered
in some instructions, I was able to interface up to 64Mb dram to the Z80
with only 2 TTL support chips, and had to refresh the drams at a
constant minimum timing, else they dropped their bundle. Z80 memory map
range is quoted at 64K.

Documented at: http://www.dontronics.com/z80.html for interested parties.

MSP430 is something that is gathering momentum, and will give PIC and
AVR families a big shunt.

Bob's beloved Z8 Encore I'm sure I would have loved also, but again, my
development years are far behind me.

Don...


Don McKenzie
E-Mail Contact Page:               http://www.dontronics.com/e-mail.html

Crystal clear, super bright OLED LCD (128x128) for your microcontroller.
Simple serial RX/TX interface. Many memory sizes.
http://www.dontronics-shop.com/product.php?productid16%460

Re: joy in assembly


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C'mon Don,
    You know what they say about riding bikes.... :-)

Bob

Re: joy in assembly



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Possibly true, but at least bicycles haven't changed in over 200 years,

Re: joy in assembly


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    The basic principles of programmable digital electronics haven't
changed since Alan Turing & many others worked them out a long time
ago... :-)


Re: How to check 125 logic states...?


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Programming in high level language definitely makes using PICs a lot
easier (and pleasant). There is always a concern that the code is less
optimized or apparent lack of full control of the code but I have looked
at the assembly output of some of my projects (the ones that did not run
first time so that would be 100%) and really compiler produced code is
not that bad although I found the resultant code size varies wildly
between compilers. However, as long as the code produced is correct and
you application is not timing or space sensitive one it really doesn't
matter if you use up 50% of the code space or 55% of the code space
since you're paying per chip.

As for great marketing, I don't know how much Microchip did to promote
PICs but one thing they did do right - the chip is easily obtainable and
reasonably cheap which is not the case for the comparable competing 8
bit MCUs. It is a fair bit harder to get Atmel or MCP430 MCUs (although
nowadays I found Dontronics and Futurlec stock those). As a result,
although competing MCUs have nicer ISA and they have free compiler
toolchains (I think one can get gcc for Atmega, MSP430 and ARM) while
PIC doesnt really have a good free C compiler, PIC is more popular than
the others. Because of that there seem to be more resources on the net
related to PICs (programmers, projects, code snippets) which no doubt
catches peoples attention.

Eugene.

Re: How to check 125 logic states...?


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    All good points. My problem is that often the timing is important,
plus I tend to underestimate how much program memory I'm going to need,
and design around a chip which doesn't have quite enough. Some of my
projects have used all but the last ~30 bytes of memory. :-)
    Certainly Microchip have done their homework and made devices and
support readily available for people just getting into micros, knowing
that they probably won't change to another architecture/brand once
they're used to using PICs. Other companies have aimed for professional
users, so no-one else uses them and new users never hear about them.
    I'm using Zilog Encore micros now. Zilog are making their full
Development Suite which includes a full C compiler available for anyone
to download. See
http://investor.zilog.com/phoenix.zhtml?c10%7835&p=irol-newsArticle&t=Regular&id90%0003 &
    The Encore is a good flash micro family with OCD and simple
single-pin interface. It's a shame it's not better known.

Bob







Re: How to check 125 logic states...?


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http://investor.zilog.com/phoenix.zhtml?c10%7835&p=irol-newsArticle&t=Regular&id90%0003 &
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It is a good move by Zilog to offer their development suite and C
compiler free. It should help them in a long run, having a free C
compiler is nearly an expectation on 32 bit architectures now and I
think it will tend to go that way in smaller MCU area also.
I wonder if the 8bit devices will eventually all be replaced by 16 or 32
bit parts in the future. Seems an overkill but low end ARM chips are
cheaper than ever and with the speed at which semiconductor technology
moves forward it is hard to make a definite prediction on anything
without fear of being proven utterly wrong (ala infamous Bill Gates
quote that noone will need more than 640KB RAM).

Eugene.

Re: How to check 125 logic states...?


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    I seem to recall that Bill also said that e-mail spam would be a
problem of the past by 2006. He probably shouldn't give up his present
job to become a clairvoyant!
    You only need to look at how the prices on USB memory sticks are
dropping to see the trend towards putting more and more active
components onto smaller and smaller bits of silicon.
    It mightn't be all that long before 16 bit micros are everywhere,
followed by 32 bit ones, pushing 8 bit devices into the background and
maybe into history too.

Bob


Re: How to check 125 logic states...?


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The top quality PIC C compilers (like HI-Tech) generate very space
efficient and fast code.

If the reason you are using assembler is to squeeze your program into a
specific chip, then you have chosen the wrong chip.

Professional microcontroller work is done mostly in C, with a small
amount of in-line assembler where needed. The benefits of much faster
development time, ease of code peer review, and code portability are
massive benefits that only a fool would pass up.

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The Microchip 18series PIC C compiler is available for free, with I
believe one minor limitation on code speed and optimisation.

Dave :)


Re: How to check 125 logic states...?


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    It sorta depends on the scale of the project. Obviously an
automotive engine control system (for example) is so complex that you
couldn't do it in assembler.
    My projects are small one-person designs dedicated to a relatively
simple task and no-one else will ever look at the code, so I've never
been terribly motivated to learn C.
    One day I might get into C, but it won't be on PICs on principle. :-)


Cheers
Bob


Re: How to check 125 logic states...?


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    It's an interesting idea. In fact I was once working on a design for
identifying wires in a cable which used a principle something like that,
with groups of resistors at the far end.
    In this case, I already have a working circuit board based on a nice
Zilog Encore micro, looking at 50 lines with 7 x 74LS165s. I've been
asked to increase that to nearly 130 lines and I was looking for the
simplest way to make the change without radically changing the rest of
the design.
    Some useful design ideas have popped up during this discussion. :-)

Regards
Bob


Re: How to check 125 logic states...?


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Any possibilty of simply stacking 3 of the existing boards?

Dave :)


Re: How to check 125 logic states...?


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   We could do that, though it would make it hard to see the
alphanumeric LCD module and push the buttons on the bottom two. ;-)

   I think Brenden was right - simply string together as many readily
available cheap simple 74HC165s as needed (16).

   This little discussion's thrown up some interesting ways of solving
this unusual problem. :-)

Bob





Re: How to check 125 logic states...?


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I've just designed a similar system, albeit with fewer (and non-binary)
"bits".

I have also done something analagous: measured the outputs of 120
(modulated) photodiode detectors combinatorially, using 16 x
BPF-FD-comparator stages (2C16 = 120), but I doubt thats applicable
here. besides SREGs are cheap.

Cheers
Terry

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