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'Any opinions on the Scenix Sx MPU? (Please Forgive'
1998\09\11@123003 by David Blain

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I must apologize for that message being re-posted to the list in HTML.  I
just reconnected a mail server that has been offline for a while and this
message was sent from a queue that should have been deleted!

As for a follow-up:

I did decide to go with the SX.  The programming time of 50-100 ms per word
doesn't bother me.

So far I have been impressed with the ease of use.  I don't mind using Win9x
to develop in (I have a old 486 that I dedicated to this), however, I do
wish they would supply command line tools for programming, so that I may use
a real code editor instead of there IDE.

I am using the In Circuit Programming feature, and find it extremely nice
for prototyping.  I only need a 4 pin header on the board, and have to
remember to remove a jumper to disconnect the Oscillator before programming.
(I got the Tristate version so I could design a way to disable it during
programming automatically, but I have no clue how to do it yet!)

As most of you know, not having to erase the chip prior to programming is a
timesaver.  I have programmed the chip 5-6 times in a 10 min. time frame.
(I like to learn by making small changes and see what happens... I will
probably ruin the chip by the time I'm done prototyping, it's a small price
to pay for the amount I am learning.)

Here's a little background on the project I am working on:

The first part of my project that I am currently prototyping is for the
HVAC.  I will have 5 Zones, all talking to a central zone controller through
a rs-485 multi drop network.  The zone controller will be responsible for
controlling both the HVAC unit as well as all of the dampers.  The
Thermostats will all be programmable from a main computer as well as from
each other.  (I want to be able to control/view the temp in any zone from
any other zone.)  They will also have the ability to display a dynamic
menu/messages that are uploaded from the main computer system.

The parts that I have chosen for the thermostats are as follows (This is
also my base design for future nodes):

       28 pin 2k Scenix SX as the MPU.                 ( $6.89US in singles )
       CTS Tristate 50 Mhz Oscillator                  ( May drive more than on
e MPU )
       Dallas DS2401 Silicon Serial Number             ( Network MAC address )
       Microchip 24C32 Serial EEProm   I2C                     ( Storage for Me
nus/Messages/Thermostat
information )
       Dallas DS1307 Serial Real Time Clock I2C
       Dallas DS1621 Serial Digital Thermometer I2C
       Maxim MAX487                                            ( For Multi Drop
RS-485 Network )
       Optrex 16x2 LCD                                         ( or 16x4... hav
e both, not sure which will work
better for the app.)

I have wired everything up on a bread board(s) and have started the learning
process for using each component.  At this time I have been able to get a
LED flashing, I HAD to do it at least once... IMHO it is the 'Hello World'
program for Electronics, written multi-purpose routines for accessing the
LCD, and thanks to a subscriber to the list, am currently converting a 'C'
snippet to asm for reading the DS2401.

I have a long way to go to get all of the functionality I am looking for,
but I feel I am making progress.  (I have only had the hardware for 2 weeks,
and it is my first project ever.)  This list has been invaluable to me in
getting the courage to even get started!

I do have a question for the list (I have many, but this one I have no clue
what the correct solution might be.)

The question(s) is...

       I want to supply the power from a centralized location to the thermostat
s
over the Cat-5 Cable that I am going to use for the data network.

1) Should I use one pair for both supply and return or 2 separate pairs one
for supply and one for return? (The same pair seems like a bad Idea, but I
don't quite know why)

2) Should I put a voltage regulator (7805) at each thermostat and have the
supply be unregulated or have the main supply be regulated with nothing more
that a Cap./resistor at each thermostat. (Would the heat from the 7805
affect the Temperature reading?)

I am curious about any comments that anyone has, good or bad, about the
project that I have thrust upon myself.

Thanks again for everyone's past and future help.

David
(In over my head so much I must breath through a straw!)


{Original Message removed}

1998\09\11@170043 by paulb

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David Blain wrote:

> Dallas DS1307 Serial Real Time Clock I2C

 Do you really need this?  The central site could poll the peripherals
each second, sending the time in the poll.  If you wanted, an "alive"
LED could pulse each poll.

> 1) Should I use one pair for both supply and return or 2 separate
> pairs one for supply and one for return? (The same pair seems like a
> bad Idea, but I don't quite know why)

 One pair should do.  The ground return resistance/ drop won't matter
with RS-485.

> 2) Should I put a voltage regulator (7805) at each thermostat

 Good idea.

> and have the supply be unregulated

 Supply would still be modestly regulated.

> Would the heat from the 7805 affect the Temperature reading?

 Yes!  The penalty for local regulation is that you double the local
heat (assuming 10V supply).  Local heat generation is a problem you
have given yourself by using a Scenix clocked at 50MHz!  You need to
locate the DS1261 well away from and *BELOW* the regulator *and the
Scenix*!  Note I say *below*.  Convection from the heat-producing
devices could actually improve your sensing accuracy if vents are top
and bottom only.
--
 Cheers,
       Paul B.

1998\09\11@173545 by David Blain

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>> Dallas DS1307 Serial Real Time Clock I2C
>
>Do you really need this?  The central site could poll the peripherals
>each second, sending the time in the poll.  If you wanted, an "alive"
>LED could pulse each poll.

I wanted each to have there own Real Time Clock for 2 reasons:

       1) So that they could run standalone, without the main computer,
and possibly as a single zone device.  ( No central Zone Controller )

       2) I am planning on using the same board, minus the temp sensor,
as a base for other devices. (i.e. Sprinkler controller, Security
Monitor...)

Thanks for your suggestions... I will definitely keep the heat issue in
mind!

David.

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<BR>
<BR>
<P><FONT SIZE=2>&gt;&gt; Dallas DS1307 Serial Real Time Clock I2C</FONT>
<BR><FONT SIZE=2>&gt;</FONT>
<BR><FONT SIZE=2>&gt;Do you really need this?&nbsp; The central site could poll
the peripherals</FONT>
<BR><FONT SIZE=2>&gt;each second, sending the time in the poll.&nbsp; If you wan
ted, an &quot;alive&quot;</FONT>
<BR><FONT SIZE=2>&gt;LED could pulse each poll.</FONT>
<BR>
<BR><FONT SIZE=2>I wanted each to have there own Real Time Clock for 2 reasons:<
/FONT>
<BR>
<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <FONT SIZE=2>1) So that they coul
d run standalone, without the main computer, and possibly as a single zone devic
e.&nbsp; ( No central Zone Controller )</FONT></P>
<BR>
<P>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <FONT SIZE=2>2) I am planning on u
sing the same board, minus the temp sensor, as a base for other devices. (i.e. S
prinkler controller, Security Monitor...)</FONT></P>
<BR>
<P><FONT SIZE=2>Thanks for your suggestions... I will definitely keep the heat i
ssue in mind!</FONT>
<BR>
<BR><FONT SIZE=2>David.</FONT>
</P>

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1998\09\11@175337 by David Blain

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***I don't think this made it intact... Ignore if a duplicate


>> Dallas DS1307 Serial Real Time Clock I2C
>
>Do you really need this?  The central site could poll the peripherals
>each second, sending the time in the poll.  If you wanted, an "alive"
>LED could pulse each poll.

I wanted each to have there own Real Time Clock for 2 reasons:

       1) So that they could run standalone, without the main computer, and
possibly as a single zone device.  ( No central Zone Controller )

       2) I am planning on using the same board, minus the temp sensor, as a ba
se
for other devices. (i.e. Sprinkler controller, Security Monitor...)

Thanks for your suggestions... I will definitely keep the heat issue in
mind!

David.

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