From: Spehro Pefhany
Subject: Re: PIC/Microcontroller recommendation?
X-Newsreader: Forte Agent 1.92/32.572
Date: Tue, 17 Dec 2002 14:53:06 GMT
NNTP-Posting-Date: Tue, 17 Dec 2002 09:53:06 EST
On 16 Dec 2002 21:26:51 -0800, the renowned firstname.lastname@example.org (Mike)
>I like that idea....now I can change my design before I even get
>Have extend, retract and stop pushbuttons as originally stated.
>Instead of the two pots, have (1) 3 position toggle switch. Positions
>would be manual, auto and set.
>When in manual position, extend and retract "jog" (or run) the
>respective motors; hardcode a min and max position to avoid
>overrunning the motor.
>When in set position, pressing extend or retract stores the current
>arm position as the limit. So in manual mode, you'd put the arm where
>you want it, then switch to set and store the appropriate limit.
>When in auto position, 3 buttons act as originally described, but the
>limits are those set via the above procedure, instead of by the pots.
>Based on the statement below, I assume some of the microcontrollers
>discussed have the ability to store data in nonvolatile memory during
>standard program running operation?
All the PICs that we've recommended do. If you're doing that, you
need an ADC, so the 16F870 (or 873 or 876 which are more expensive
and have more memory, which you don't need) would be an okay start.
If they didn't you could easily hang a small EEPROM onto any
micro, but as the other kind of chips are reasonably priced and
available, no need. Use the data EEPROM rather than attempting
to write to program FLASH, as it's significantly easier.
As you add this kind of sophistication, you should think about
the development process. It's easy to run this stuff in simulation
and prove most of the program, but some things (external inputs)
are harder to simulate than others.
If you want to check it out further, have a look at the
data sheet and the supplementary "midrange reference manual.
For tools, maybe pick up an ICD2, which requires the MPLAB6.10
software and USB. Keep in mind that officially Microchip
designates the ICDs and the PICstart+ as "development" programmers as
they don't verify at different Vdd levels. To do "proper"
production programming, a more expensive programmer is required.
>That would be me. I figure easier to learn this than get out my
>circuit design and logic books and start from square one building
>logic circuitry though.
It will not be easier (the two documents above total almost 1,000
pages), nor cheaper unless you homebrew most everything but the
experience will probably be useful in the future. It's one hell
of a lot cheaper than it was when I got started- a development
system would be limited to one family and might cost $15K, back
when that was real money.
"it's the network..." "The Journey is the reward"
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