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A Call for A2D Recommendations... — Parallax Forums

A Call for A2D Recommendations...

ArchiverArchiver Posts: 46,084
edited 2003-09-18 03:54 in General Discussion
Hi all,

Well I given up trying to get the MAX186 to work with my BS2 (I only ever get
0.000 or 4.096 Volts as readings!!!). I've been using Shaun Wilsons webpages
(http://geocities.com/SiliconValley/Orchard/6633/max186.html) it's the only
website I could find regarding MAX186 and BS2, but to no avail! Its a shame, as
I managed to get a total of 6 samples of them from Maxim!!

So I'm now after a replacement A2D that I can ideally source in the UK. I was
thinking of using two LTC1298's with the data and clock lines bus'ed together
and then two seperate chip select lines. I've tried to find if Linear Technology
do a 8 channel version of the LTC1298 but I can't quite work out there range!!!
These are all 12 bit but I guess 10 bit will do for what I want...

So anyone got any ideas... like I say ideally that I can get in the UK...

Thanks all, keep up the great work...


Kev/.


[noparse][[/noparse]Non-text portions of this message have been removed]

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-09-17 21:56
    This almost sounds like your input voltage source is not sharing the same
    ground
    as the MAX186. I looked at the web-page you suggested along with the code and
    although the code doesn't provide much in the way of detail, if you look at
    what
    it sends to the MAX186 for channel 0.... 142 decimal or (10001110 Binary) this
    corresponds to the correct setup for channel 0 according to the datasheet. I
    find it difficult to believe that all 6 of your devices are failing, but since
    they are all acting the SAME this should be your first clue that this might be
    a hardware issue. Once you have confirmed that it is not in software. I would
    double check your wiring or even better, build the circuit a second time on
    another (separate) bread-board. If you still see the same results, break down
    the software code to a more step-by-step over simplistic level until you are
    absolutely sure what each line of code is doing and go from there.

    Another thought... Are you positive that ALL of your pins on your stamp are
    functioning properly? i.e. You haven't fried any lately.


    -Beau Schwabe


    >Hi all,
    >
    >Well I given up trying to get the MAX186 to work with my BS2 (I only ever
    >get 0.000 or 4.096 Volts as readings!!!). I've been using Shaun Wilsons
    >webpages (http://geocities.com/SiliconValley/Orchard/6633/max186.html)
    >it's the only website I could find regarding MAX186 and BS2, but to no
    >avail! Its a shame, as I managed to get a total of 6 samples of them from
    >Maxim!!
    >
    >So I'm now after a replacement A2D that I can ideally source in the UK. I
    >was thinking of using two LTC1298's with the data and clock lines bus'ed
    >together and then two seperate chip select lines. I've tried to find if
    >Linear Technology do a 8 channel version of the LTC1298 but I can't quite
    >work out there range!!! These are all 12 bit but I guess 10 bit will do
    >for what I want...
    >
    >So anyone got any ideas... like I say ideally that I can get in the UK...
    >
    >Thanks all, keep up the great work...
    >
    >
    >Kev/.
  • ArchiverArchiver Posts: 46,084
    edited 2003-09-17 22:34
    Hi, thanks for the reply

    These MAX186s have had me tearing my hair out for over a month now! I've
    tried everything.
    Two different bread boards, and a lashed up stripboard. My test input is a
    4.7K pot across the BoE power rails acting as a potential divider.
    I've tried nearly every possible combinations of pins. I even started
    labeling wires!!!
    There are about four ground interconnections between the various devices.
    I've tried pull ups and pull downs on the bus but this just forces the input
    to all high or all low.
    I've tried with and without hte op-amp input circuit. Still nothing...
    I've connected all the unused inputs (4-7) to ground but the debug still
    randomly shows some of these

    A multimeter shows the clock line is going up and down as it should, but the
    stamp never reads any data in.

    I'd really like to use the MAX186's, maybe this weekend I take some
    pictures/do some diagrams of what I have setup...

    I've just bought the LTC1298 app kit from Milford Instruments (20 GBP) and
    got it working perfectly in about 10 minutes flat!!!
    The kit is just the IC, and one capacitor, manual and a floppy with the
    source code on. Very useful for the first one but a bit pricey for building
    up projects with.

    I guess the very last final thing to try is another Stamp. I only have one
    BS2... the basic green one. Would it be worth getting a different one
    SX/P??? to try???

    Cheers for your input, although at the moment it's only digital and not
    analogue!!!!!!! (bad joke I know, sorry all)


    Kev/.


    Original Message
    From: "Beau Schwabe" <bschwabe@a...>
    To: <basicstamps@yahoogroups.com>
    Sent: Wednesday, September 17, 2003 9:56 PM
    Subject: Re: [noparse][[/noparse]basicstamps] A Call for A2D Recommendations...


    > This almost sounds like your input voltage source is not sharing the same
    > ground
    > as the MAX186. I looked at the web-page you suggested along with the code
    and
    > although the code doesn't provide much in the way of detail, if you look
    at
    > what
    > it sends to the MAX186 for channel 0.... 142 decimal or (10001110 Binary)
    this
    > corresponds to the correct setup for channel 0 according to the datasheet.
    I
    > find it difficult to believe that all 6 of your devices are failing, but
    since
    > they are all acting the SAME this should be your first clue that this
    might be
    > a hardware issue. Once you have confirmed that it is not in software. I
    would
    > double check your wiring or even better, build the circuit a second time
    on
    > another (separate) bread-board. If you still see the same results, break
    down
    > the software code to a more step-by-step over simplistic level until you
    are
    > absolutely sure what each line of code is doing and go from there.
    >
    > Another thought... Are you positive that ALL of your pins on your stamp
    are
    > functioning properly? i.e. You haven't fried any lately.
    >
    >
    > -Beau Schwabe
    >
    >
    > >Hi all,
    > >
    > >Well I given up trying to get the MAX186 to work with my BS2 (I only ever
    > >get 0.000 or 4.096 Volts as readings!!!). I've been using Shaun Wilsons
    > >webpages (http://geocities.com/SiliconValley/Orchard/6633/max186.html)
    > >it's the only website I could find regarding MAX186 and BS2, but to no
    > >avail! Its a shame, as I managed to get a total of 6 samples of them from
    > >Maxim!!
    > >
    > >So I'm now after a replacement A2D that I can ideally source in the UK. I
    > >was thinking of using two LTC1298's with the data and clock lines bus'ed
    > >together and then two seperate chip select lines. I've tried to find if
    > >Linear Technology do a 8 channel version of the LTC1298 but I can't quite
    > >work out there range!!! These are all 12 bit but I guess 10 bit will do
    > >for what I want...
    > >
    > >So anyone got any ideas... like I say ideally that I can get in the UK...
    > >
    > >Thanks all, keep up the great work...
    > >
    > >
    > >Kev/.
    >
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed. Text in the Subject and
    Body of the message will be ignored.
    >
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    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2003-09-18 03:54
    I would say that you have a wiring problem. I use the MAX186 in about
    8 different projects without problems, each one hand wired in curcuit
    using point to point construction. Double check each connection. You
    should be able to measure the reference voltage out from the IC. It
    should be 4.096 volts +- a few mv. Also do not exceed this voltage on
    any of the analog inputs. Doing so may cause latch up. Be sure that
    VSS pin 9 is tied to ground and Pin 10 should be left floating or
    pulled high with a 4.7k resistor.

    Jason


    > Well I given up trying to get the MAX186 to work with my BS2 (I
    only ever get 0.000 or 4.096 Volts as readings!!!). I've been using
    Shaun Wilsons webpages
    (http://geocities.com/SiliconValley/Orchard/6633/max186.html) it's
    the only website I could find regarding MAX186 and BS2, but to no
    avail! Its a shame, as I managed to get a total of 6 samples of them
    from Maxim!!
    >
    > So I'm now after a replacement A2D that I can ideally source in the
    UK. I was thinking of using two LTC1298's with the data and clock
    lines bus'ed together and then two seperate chip select lines. I've
    tried to find if Linear Technology do a 8 channel version of the
    LTC1298 but I can't quite work out there range!!! These are all 12
    bit but I guess 10 bit will do for what I want...
    >
    > So anyone got any ideas... like I say ideally that I can get in the
    UK...
    >
    > Thanks all, keep up the great work...
    >
    >
    > Kev/.
    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
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