Sequencing SAR how to make  internal connection to input

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Jweaver
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I have the cy8ckit-059 ,  using the sequencing SAR (single ended),  there's a compile error if  the analog input is connected to an op-amp output internally.  Is the only solution to bring the op-amp output to a pin and also the analog input of the SAR to a pin,  then connect them with a wire externally? (I'm only using one-input for now, but I will be using 2 inputs later).

   

Why can't there be a direct connection, all internal, from op-amp output (internal) and SAR input ?   I don't have this problem with the Delta-sigma A/D.  Why?

   

That's all one question.   

   

Another question- everytime I open the SAR part to configure, it changes the frequency.  Originally  I set it to 1 MHz,  but it reverts to 999.992 kHz  .  

   

Thanks in advance

   

Jim

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Anonymous
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Hi,

   

For the ADC I ran into the same problem (see replies http://www.cypress.com/forum/psoc-creator-software/creator-error-signal-ah0degw-expected-connect-onl...). I had to go with ADC SAR+AMux instead of the Sequencing SAR, as I didn't like the external connection between "internal" OPAMP and sequencing SAR.

   

Regards,

   

Matija

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Jweaver
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Here's the project file

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Bob_Marlowe
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First page of Seq ADC datasheet says:

   

Note Only GPIOs can be connected to the channel inputs. The actual maximum number of input channels depends on the number of routable analog GPIOs available on a specific PSoC part and package.

   

Set the clock frequency a bit higher than 1 MHz, ADC will display 1000.020 kHz

   

 

   

Bob

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Anonymous
Not applicable

Hi,

   

For the ADC I ran into the same problem (see replies http://www.cypress.com/forum/psoc-creator-software/creator-error-signal-ah0degw-expected-connect-onl...). I had to go with ADC SAR+AMux instead of the Sequencing SAR, as I didn't like the external connection between "internal" OPAMP and sequencing SAR.

   

Regards,

   

Matija

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Jweaver
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Yes,  that's what I'm doing too. But still the question remains.  Why does one allow for internal connections and the other doesn't?  I can guess,  like maybe they didn't see the point of it- if you have more than 4  inputs that you want buffered, this has to be done externally anyway.  So they didn't bother to  include this design feature.   That's a guess...

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Jweaver
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ok-  I just read your link.  That answers my question. Thanks a lot.

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