PIC Programmer

[Peter Gargano]

My 2 cents worth on the PIC...

Simon Quested wrote:

> A$25 for a starter kit...
> Is this the sort of thing that is good for a complete beginner in PICs?
> (like me)

I think that it's very good value, BUT, you have to ask yourself why
you're going to use a PIC. These devices are great for performing
many small logic functions - and the Scenix devices (fast PIC clones) 
seem to be fast enough to even replace existing hardware devices
(perhaps even a slow CPU).

The biggest drawback is that the PIC has only small amounts of program
memory. This is built into the architecture and means that larger
projects are much harder to program because you have to worry about
things like your code crossing a page boundary, etc.

Traditional microprocessor architectures like the 68HC11, 68332, etc.
can access lots of program memory and are not limited in the same way
a PIC is. On the other hand, to do anything with one of these "bigger"
chips, you have to write a lot of code just to get the CPU to power
up its internal circuitry and talk to the outside world.

You may have heard about the Basic Stamp (and like clones) that can
be programmed in BASIC (or even C). These devices use a PIC chip,
but they read an external program (usually stored in a serial EEPROM).
For each high level instruction it interprets, the PIC has to
read the EEPROM, decode what is required, then do it. This slows the
PIC down by orders of magnitude compared to running from its "native"
mode, and compared to an a "traditional" microprocessor. In general
a Basic Stamp (or similar) is NOT suitable for an EFI project. On the
other hand, a simple ignition controller is quite do-able (Jaycar also
have a PIC ignition controller kit!).

I have to be honest and say that if you want to get into programming
micros then one of the best things to do is get something like an
Apple II or C64, etc. People are throwing them out and you can get 
them for nothing (perhaps someone will pay you to take one away!). 
Get a book about programming, spend some time getting to know how
to program your CPU, and then, if you're still motivated, AND you
really have something you want to program, team up with one of the
current EFI332 projects and you'll be in a position to understand
what's happening.

If you do get say an Apple, what you'll learn may not be about the
same micro that's in a particular ECU (although the 6502 is not
unlike the 6800 which is the basis for the 68HC11 which is used
in many GM ECUs) but it will give you a basis for understanding
how the microprocessor in the ECU works - that has to be good for
something!

regards,
-- 
Peter Gargano