🚀 go-pugleaf

Gerhard Glatte wrote:

> Hello Newsgroup,
> 
> my name is Gerry and I currently work with a group on our diploma project
> (that's the final exam period of my school type). In this project we use the
> MAX195 16bit analogue digital converter.
> 
> We have now the following problem:
> We made a printed circuit board and control the MAX195 directly with a PIC
> microcontroller (PIC16F877). The MAX195 converts the analogue signal
> correctly, but nearly every 3 seconds (it seems to be a periodic process)
> the converted voltage "jumps"(e.g. from 1,12568 to 1,13568), but the
> analogue signal (which has to be converted) does not.
> 
> We clock out the data serially (after the conversion) by setting the SCLK
> pin high and low (controlled by the microcontroller).
> 
> If anyone of you has experiences with this ADC please help us,
> we are trying to solve that problem for weeks without any results,
> 
> Gerry
> 
> 


Test

Gerhard Glatte wrote:

> Hello Newsgroup,
> 
> my name is Gerry and I currently work with a group on our diploma project
> (that's the final exam period of my school type). In this project we use the
> MAX195 16bit analogue digital converter.
> 
> We have now the following problem:
> We made a printed circuit board and control the MAX195 directly with a PIC
> microcontroller (PIC16F877). The MAX195 converts the analogue signal
> correctly, but nearly every 3 seconds (it seems to be a periodic process)
> the converted voltage "jumps"(e.g. from 1,12568 to 1,13568), but the
> analogue signal (which has to be converted) does not.
> 
> We clock out the data serially (after the conversion) by setting the SCLK
> pin high and low (controlled by the microcontroller).
> 
> If anyone of you has experiences with this ADC please help us,
> we are trying to solve that problem for weeks without any results,
> 
> Gerry
> 
> 

Hi

You'll probably have a timing failure.

Datasheet:
The data bits can be read either during the conversion, at the
CLK clock rate, or between conversions asynchronous with CLK at the SCLK 
rate (up to 5Mbps).
/Datasheet

Do you monitor EOC?

Do you use TRACK/HOLD?

Is it possible you do a dataread during calibration?

Any noise on the power supply lines?

Quite some possibilities to mess up a measurement... Sorry I don't have 
an out-of-the-box solution for you...

On Wed, 25 Feb 2004 20:09:20 +0100 "Gerhard Glatte"
<gerhard.glatte@world4you.com> wrote in Message id:
<c1irvj$sal$1@newsreader1.utanet.at>:

>Hello Newsgroup,
>
>my name is Gerry and I currently work with a group on our diploma project
>(that's the final exam period of my school type). In this project we use the
>MAX195 16bit analogue digital converter.
>
>We have now the following problem:
>We made a printed circuit board and control the MAX195 directly with a PIC
>microcontroller (PIC16F877). The MAX195 converts the analogue signal
>correctly, but nearly every 3 seconds (it seems to be a periodic process)
>the converted voltage "jumps"(e.g. from 1,12568 to 1,13568), but the
>analogue signal (which has to be converted) does not.

Due to the fact that the incorrect result is off by only one bit, as a
guess, I'd say that either your clock is not properly synchronized to
your data (Try shifting the clock a bit) or your design has a dropout on
the serial clock - because it seems to occur on a regular basis, perhaps
the PIC is busy running some subroutine or something?