RE: AD converters

[Nigel Orr <Nigel.Orr@xxxxxxx>]

At 10:09 15/06/00 +0100, you wrote:
>These PIC jobbies have cropped up a couple of times, and sound dead
handy.
>How expensive is it to get started with them, and are they simple
enough f=
or
>a VB/C++ programmer to get the hang of?

Assuming you want a fairly quick start (ie you don't want to build your
own=
=20
programmer), probably =A3100-150 for the official Microchip PICStart=20
programmer, MPLAB assembler software is free.  The assembly language is=20
quite easy (I'd rate it as similar to Comfort, which might be a better=20
comparison :-) ), and the documentation is good (again, similar to=20
Comfort!).  There are also loads of application notes covering various
desi=
gns.

C compilers are available, but I've never used them.  PICs don't have much=
=20
memory to allow the code to 'bloat', and besides, I'm a nerd... :-)

There are various devices with various amounts of built-in memory,
serial=20
ports, parallel ports, ADCs, DACs etc etc, an increasing number have FLASH=
=20
memory (they have an 'F' early in the part number- like 16F84), rather
than=
=20
the older EPROMs (with a 'C' in the part number)- go for the FLASH ones if=
=20
you can, it's a pain to have to keep erasing EPROMS under ultraviolet when=
=20
you are debugging (assuming you won't want to spend =A31000 on a
hardware=20
debugger...).  I haven't bought any recently, but I think the FLASH
chips=20
are under a tenner.

Building the circuits is particularly easy- they can source or sink up
to=20
25mA, and have all the clock driving circuits etc built in, as well as=20
program memory and some data memory, so you can add a crystal, 2
resistors,=
=20
a switch, an LED and 2 capacitors, and the circuit is complete.  That's
the=
=20
bit that appeals to me- Z80's were all very well, but the amount of
fluff=20
needed to actually use one to flash an LED was less appealing!

And power consumption is low, allegedly down to <2uA in sleep mode, but
I=20
haven't managed that (or needed to!) yet.

>Oh, and I'd still want to upload the data to a PC ultimately - is that
>asking too much (in terms of my ability to it)?

Some have built-in USARTs, I used them last year for a parallel to
serial=20
to parallel converter (to connect a device to a PC parallel port down 150m=
=20
of cable), and they're _fairly_ straightforward if you understand how=20
serial ports work and even more so if you have access to an oscilloscope
to=
=20
see what is going on.

HTH, if you want more info, read some of the data sheets at=20
http://www.microchip.com, the
PICLIST site at http://www.piclist.com (or is=
=20
it .org), or even ask me!

Nigel


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