LPC812 - HVAC controller - eval chip

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olzeke51
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Location: South Carolina

LPC812 - HVAC controller - eval chip

Post by olzeke51 »

I am wanting to help eval the LPC812 , so I got the sample, and am now going to use it as a
basic HVAC controller for my cabin & woodstove & ventilating fans.

I want to use the A/D comparator to set my temperature threshold. A 10K pot to do the
setpoint and an IC temp sensor for the other analog input. I will attempt to use the
register for a 'comp flag' as I don't have enough pins to use the 'comp_out' pin.

Brief scan of the C help file doesn't come up with any a/d comparator type of help info,
nor the forums [ in fact 'a/d' won't search - it reports back that 'a d' is not valid - needs
3 characters !!! ]

Bruce, have you started/completed any rough info ?? If not , I would try to provide some
basic info that should fit into the Help file and also perhaps a adcomp.c & .h file. I
don't want to duplicate what you may have already done. Any guidance/direction would
be accepted - I want to help and not be a NOOB PTA !!

feel free to put this in an appropriate place -
should I add to the post as I go along or put individual items in their own post? (in one of
the other forums?)

Thanx, gz aka olzeke51



basicchip
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Re: LPC812 - HVAC controller - eval chip

Post by basicchip »

The 812 does not have any A/D channels, it is a purely digital part.

olzeke51
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Location: South Carolina

Re: LPC812 - HVAC controller - eval chip

Post by olzeke51 »

True - it doesn't have a/d channels, however
there are two pins that feed an A?D comparator and one output pin (matrix enabled on all 3 pins)
Page 8 of my product data sheet lists that as being on pins 19, 12 and 18 for output.

basicchip
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Re: LPC812 - HVAC controller - eval chip

Post by basicchip »

There won't be any builtin support for the comparator in BASIC, but you can enable that function and access the comparator using register read/writes in BASIC. Details on how to do that in chapter 13 of the NXP User manual.

I haven't written any code for that function yet.

olzeke51
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Location: South Carolina

Re: LPC812 - HVAC controller - eval chip

Post by olzeke51 »

the latest MakeItC download (June 01 1600hours) doesn't include DS or UM pdfs for the LPC8xx series

basicchip
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Re: LPC812 - HVAC controller - eval chip

Post by basicchip »

Thanks for letting me know, I'll add those.

I just copy the latest versions from the NXP website and move them to the Coridium site (so that the link never breaks), but that means I may have a down rev version, until I notice or someone else does.

olzeke51
Posts: 394
Joined: Sat May 17, 2014 4:22 pm
Location: South Carolina

Re: LPC812 - HVAC controller - eval chip

Post by olzeke51 »

PROJECT ON HOLD, I need to get the well pump monitor(aka 'simple event monitor') done now - it is drought season here in So. Oregon.

olzeke51
Posts: 394
Joined: Sat May 17, 2014 4:22 pm
Location: South Carolina

Re: LPC812 - HVAC controller - eval chip

Post by olzeke51 »

Fired up the solder iron so I did some work on my '812
bought some AdaFruit arduino proto-shields, as I already had
the AdaFruit arduino-datalogger sheild. (having some trouble
with my I2C coding -- so I created the RTC_fake.bas program.
(it's in the Projects-simple event monitor).
1)I used a long-tail memory socket to mount the 812.
2)isolated the proto LED sockets - 2a)one at the end of the 'digital'
will be used for SCL/SDA connection [ the datalogger has these on
it - as well as my 'Leonardo' - but the pads on the datalogger also
had to be modified -cut the traces from the last two AD pins to the
SCA/SDA pads (evidently the earlier arduinos used the AD pins for I2c)
I added sockets so the two pins would mate with the datalogger SDA/SDC
SO - 812 SDA/SDC are wired to the two pins -- NOT the AD pins
2b)I needed a 'blinky'/test LED tied (via a 1k ohm) to +3v -- that is
the white looking jumper cable
3) the short buss across the end of the shield was wired to the +3v of
the 812 chip - CAUTION - the onboard zener is 150mwatt - ie 75ma max!!!
4) I wanted/needed an input so I wired a test jumper cable to the "S1"
switch - which goes to ground when you push it. the loose resistor will
most likely get wired to +3v for a pullup (via 1kohm)
so you have +3v ---1kohm---jumper-- N.O. switch./ .NC to ground
5)[/b]where would you be without a RESET !! - so the reset switch is
wired to the 812, but also the ICSP connector - so I could pick up the
RESET from the shield on top of the 812-(later I noticed there is a
RST pin on the voltage/ AD connector side of the shield)
you MIGHT want an RC setup on the this pin - small time delay when in
standalone mode (ie. no dongle)

6)on the edge of the serial connection(812) there were two small
thru-holes for +5, GND - which also got wired to the shield busses
FUTURE - add a 5v connector, possibly a VBAT/diode/5v regulator
7) the red LED off the end of the board is tell me that the +3v is
working - again 1kohm -- keeps the current draw low - I noticed that
the LED tends to 'brown out'/flicker sometimes so a smaller value might
be a good idea.
VOILA ! ! instant eval test bed (NOT!! - 3 TO 4 hours at least!)
812_proto.JPG
812_proto.JPG (315.41 KiB) Viewed 14253 times

SeanRodney
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Re: LPC812 - HVAC controller - eval chip

Post by SeanRodney »

Whats an eval chip in HVAC controller?

olzeke51
Posts: 394
Joined: Sat May 17, 2014 4:22 pm
Location: South Carolina

Re: LPC812 - HVAC controller - eval chip

Post by olzeke51 »

Coridium offered (still is, I believe) an LPC812 chip to evaluate.see the home page
So, I needed a project to test it out - so I created my own HVAC controller project.
Basically it would monitor temp via I2C, display it on an LCD, and turn on/off some
fans for ventilation/circulation [Heating Ventilation And Circulation!!]
I have a woodstove for heat-BTW.
Regards, olzeke51
PS. it is backburnered -- the AD comparator conflicts with the serial data and reset pin

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