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'[PIC] Which PIC to chose?'
2004\10\12@190246 by Olin Lathrop

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> It does beg a question from the pro side of the fence though: How do you choose
> the right part for a particular job? Do you start with the smallest/cheapest
> part then iterate as needed for more features? Or is it better to prototype
> with more than you need, then pick the chip that fits the final software? Or
> is cost the ultimate arbiter?

I usually scope out what hardware features are needed, then pick the cheapest PIC that has them.  I usually get samples of that PIC within its subfamily that has the maximum RAM and program memory.  The volume purchases happen later after we know how much of that is needed so a scaled down PIC with the same hardware can be chosen.  For example, I would develop with a 18F252, but spec out 18F242 for production if everything fits.

> And as cool as the 10F family is, it's tough for a novice (or even intermediate)
> hobbyist to prototype with them, despite the coolness factor.

I don't think it's that hard.  It is certainly easy enough to lay out pads for a SOT-23 package.  I hear the 10F parts also come in 8 pin DIP versions for prototyping, but that makes no sense since why not just use a 12F629 in the first place since one off cost doesn't matter.

> I keep reading on the list that the higher potential speeds, banking
> simplification, and rich feature set makes the 18F family a better overall
> bet for the hobbyist. I'm just wondering if that is in fact true.

I think it is.  The extra few cents to go from a 16F876 to a 18F252 once or even a dozen times is probably below the noise floor for most hobbyists.  I was just trying to point out that there is still value in the "lesser" families, even to hobbyists in limited circumstances.  For 18 pins and up, I would advise hobbyists to stick to the 18F family.


               
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2004\10\12@200427 by Byron A Jeff

face picon face
On Tue, Oct 12, 2004 at 04:02:46PM -0700, Olin Lathrop wrote:
>
> > It does beg a question from the pro side of the fence though: How do you choose
> > the right part for a particular job? Do you start with the smallest/cheapest
> > part then iterate as needed for more features? Or is it better to prototype
> > with more than you need, then pick the chip that fits the final software? Or
> > is cost the ultimate arbiter?
>

> I usually scope out what hardware features are needed, then pick the
>cheapest PIC that has them.  I usually get samples of that PIC within its
>subfamily that has the maximum RAM and program memory.  The volume purchases
>happen later after we know how much of that is needed so a scaled down PIC
>with the same hardware can be chosen.  For example, I would develop with a
>18F252, but spec out 18F242 for production if everything fits.  >

That's lateral thinking to what I do as a hobbyist. But since it's a one off
(or maybe a two off) I just end up sticking with the bigger target.


> > And as cool as the 10F family is, it's tough for a novice (or even intermediate)
> > hobbyist to prototype with them, despite the coolness factor.
>

> I don't think it's that hard.  It is certainly easy enough to lay out pads
> for a SOT-23 package.  I hear the 10F parts also come in 8 pin DIP versions
> for prototyping, but that makes no sense since why not just use a 12F629 in
> the first place since one off cost doesn't matter.  

Exactly! In fact for an 8 pin DIP I'd choose the 12F675 under the thinking
outlined above.


{Quote hidden}

I think I'm going to step up to the 18F plate my next go round. For most of the
small projects I've been working on I've been using the 16F88 which is the
biggest and most feature packed 18 pin 16F part. But I have some 18F1330's
I believe that I think I'll give a shot on the next go round.

BAJ
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2004\10\12@201344 by John J. McDonough

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face
----- Original Message -----
From: "Olin Lathrop" <spam_OUTogl2739TakeThisOuTspamyahoo.com>
Subject: Re: [PIC] Which PIC to chose?

>  For 18 pins and up, I would advise hobbyists to stick to the 18F family.

I'm afraid that depends a lot on the hobbyist.  Most of them are easily
spooked.  The huge number of 16F84 projects out there are a great security
blanket.  Yes, I know the 18F simplifies a lot of things, but I'm amazed at
how easily frightened off many hobbyists are.  Heck, I know guys who would
rather battle communicating between a handful of 16F84's than go to a 28 pin
chip in the same family .... the unknown is very scary.  (Especially this
time of year!)

--McD


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2004\10\12@234530 by Byron A Jeff

face picon face
On Tue, Oct 12, 2004 at 08:13:43PM -0400, John J. McDonough wrote:
> ----- Original Message -----
> From: "Olin Lathrop" <.....ogl2739KILLspamspam@spam@yahoo.com>
> Subject: Re: [PIC] Which PIC to chose?
>
> >  For 18 pins and up, I would advise hobbyists to stick to the 18F family.
>
> I'm afraid that depends a lot on the hobbyist.  Most of them are easily
> spooked.  The huge number of 16F84 projects out there are a great security
> blanket.  Yes, I know the 18F simplifies a lot of things, but I'm amazed at
> how easily frightened off many hobbyists are.

I'm not. Novices want plug and play. This works fine until eventually they
have to step up to a task where plug and play doesn't work. Everyone eventually
hits that wall. You get two potential results. You describe one.

> Heck, I know guys who would
> rather battle communicating between a handful of 16F84's than go to a 28 pin
> chip in the same family .... the unknown is very scary.  (Especially this
> time of year!)

i.e. the every problem is a nail technique. The other is simply to start with
the unknown simply because it's unknown to them. One of my colleages called
it the "love what you learn" technique.

It's one of the reasons I recomment the 16F88 and the 16877A over the
lighter parts. Because whenever you get to that next stage, the tools you
need are already there.

I think that most of the 18F family fits that definition. However not having
any substative guides on using it (Peatman's book maybe? Aside: I remember
being in that guy's 68K microprocesser class 20 years ago) is damaging.

BAJ
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2004\10\13@042817 by Alan B. Pearce

face picon face
>I don't think it's that hard.  It is certainly easy
>enough to lay out pads for a SOT-23 package.  I hear
>the 10F parts also come in 8 pin DIP versions for
>prototyping, but that makes no sense since why not
>just use a 12F629 in the first place since one off
>cost doesn't matter.

agreed, along with which the 12F series has an ICD compatible device for
debugging, although I am not quite sure how one will mount it on SO-8 pads
:)) However the 12F devices are also 14 bit core against 12 bit core for the
10F devices.

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2004\10\13@043117 by Alan B. Pearce

face picon face
> Heck, I know guys who would
> rather battle communicating between a handful of 16F84's
> than go to a 28 pin chip in the same family .... the
> unknown is very scary.  (Especially this time of year!)

Guess you are going to build Olin's Halloween scarer then :))
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2004\10\13@095114 by Ian Smith-Heisters

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face
I speak as a newbie who's busily climbing the PIC18F452's learning
curve. There's a lot of resources for doing things with the 16 series,
and almost NONE for doing it with the 18. It's definitely not plug and
play. But I have to concur that the best strategy is to love what you
learn--once you've climbed the tallest learning curve around, all the
others look easy (I wanted to do electronic music so I taught myself
Pure Data, rather than Fruity Loops).

From a practical standpoint, the PIC18 offers a lot of room to grow,
and simplifies many of the programming processes if you're planning on
doing it in assembler.

If you're not already familiar with this sort of thing, or terribly
wealthy, I wouldn't recommend Peatman's book--it's only slightly less
opaque than the datasheets. There isn't a code example until chapter
five, and once you get there, it's not a simple "hello world, blink my
LED," it's some complicated mess of spaghetti, which probably just shows
my persistent ignorance. The other thing is that it costs $70, which is
about $40 too much for a glorified, bound datasheet, IMHO. It may, on
the other hand, become much more useful as I get to a more advanced
stage, it's just no good for starting from scratch.

If you need a book, you might look at Easy PIC'n and just try to
translate it to PIC18, if there isn't a new edition that includes the
PIC18. There isn't much involved in translation, at least at the early
stages.

Hope some of that helps.

-Ian Smith-Heisters


Byron A Jeff wrote:

>On Tue, Oct 12, 2004 at 08:13:43PM -0400, John J. McDonough wrote:
>  
>
>>{Original Message removed}

2004\10\13@105003 by Alan B. Pearce

face picon face
>I speak as a newbie who's busily climbing the PIC18F452's
>learning curve. There's a lot of resources for doing
>things with the 16 series, and almost NONE for doing it
>with the 18. It's definitely not plug and play. But I have
>to concur that the best strategy is to love what you
>learn--once you've climbed the tallest learning curve around,
>all the others look easy (I wanted to do electronic music
>so I taught myself Pure Data, rather than Fruity Loops).

For getting ideas about how to deal with the 18F series peripherals, you may
find the library that goes with the Microchip C18 compiler useful. Even if
not programming in C, the library examples should be readily transliterated
into assembly - least the couple I have looked at are simple enough to do
so.

It may even be practical to compile them as modules, and get the compiler to
spit out the resultant assembler code with the C code as comments. The demo
version will certainly last long enough to do that for you.

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2004\10\14@012633 by William Chops Westfield

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On Oct 13, 2004, at 9:51 AM, Ian Smith-Heisters wrote:

> If you're not already familiar with this sort of thing, or terribly
> wealthy, I wouldn't recommend Peatman's book--it's only slightly less
>  opaque than the datasheets. There isn't a code example until chapter
> five, and once you get there, it's not a simple "hello world, blink
> my LED," it's some complicated mess of spaghetti, which probably
> just shows my persistent ignorance.

I bought Peatman's boko a while ago, and have been reading it pretty
slowly.  I'm not sure I like it, and I'm not sure I understand who it
is targeted at, but I don't see how you can call it a repackaged
datasheet!
One of my objections is the speed with which he descends upon
"structured
assembler" (via preprocessor) and a sort of baby operating system (based
on running the timer); it seems to me to be a rather narrow way of
looking
at the chip.  OTOH, a problem beginners have with PICs is that there ARE
so many different ways to do the same thing, so perhaps it's not a bad
idea after all.

The book is supposedly aimed at Senior level college EE students, and
really expects that you have quite a bit of background in EE and
programming.
It is NOT a rank beginners book...

BillW

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