In message  <1.5.4.32.19970729193956.0071e520@mail.powerup.com.au>
 PICLIST@MITVMA.MIT.EDU writes:
> Hi,
>
> I'm about to start designing a small system that is to provide reasonably
> accurate temp control, drive a 2x16 or 2x20 lcd and handle12 inputs and 10
> outputs.
>
> I'm probably going to use a `74 for the job.
> I'm looking to those of you that have experience with these these things for
> advice.
>
> 1. I need to store temp setting and some other data in NV memory. I require
> about 128 Bytes. May be written to once or twice a day. Can I use the EEProm
> in the 74 for this?

No. I think that your best bet would be to use some serial EEProm
or FRAM.


>
> 2. I need a cheap but reliable 10 bit A/D with IIC. (dosen't every one?)

You could check out Maxims new 10 and 12 bits ADCs. The range is
max124x. There is a single channel version in an SO-8 package, and they
do 4 and 8 channel versions too.

One nice thing about them (although I have never used them) is that
the 10 bit and 12 bit versions are pin and software compatible making
upgrades easy (ish).

>
> 3. Is it efficient to drive the LCD from the serial port or is 4 bits on a
> parallel port the best way?

I would use 4 bits on the parallel port. There is code around the 'net
which you could use.

>
> 4. I'm planning to use a dead simple control algorithm for the temp
 controller,
> but just in case, does anyone have souce code (prefer basic) for a pid loop
> algorithm.
>
> Thanks & Regards,
> Glen Fry
> fry@powerup.com.au
> Who is very very new to PICS, but keen to have a go.
>


Regards,


Mike Watson