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Analog Routing Error when using SAR ADC | Cypress Semiconductor

Analog Routing Error when using SAR ADC

Summary: 5 Replies, Latest post by vsrs on 07 Oct 2016 07:23 AM PDT
Verified Answers: 0
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Hi there,

i want to create a measurement system using the cy8ckit-044 Pionner Kit. Therefore i need to use the SAR ADC with multiple analog inputs. I want to use 12 different analog inputs but i always get the error message "unable to fin a solution for the analog routing". When using 10 Inputs it works perfectly fine. I have used the 8 SAR ADC Pins from Port 2 + 2 Pins from a different Port. From my experience it doesnt matter which Pins i use for the last 2 but when adding another Channel to the SAR ADC I get this error. Is there a way to fix this or can i only have 10 analog Inputs? In the datasheet of the SAR ADC it says i can have up to 16 Channels. I have attached to project.

Kind Regards,

Christian Fischer

user_1377889's picture
User
10440 posts

Welcome in the forum, Christian.

I have created a support case and am waiting for an answer from Cypress. May take some time.

 

Bob

PS: You are not far away from me, I live near Bremen,

Thanks for your reply and effort Bob. Bremen is a beautiful city, i've been there a few times.

I have also tried to use MUX's  to halve the number of input pin of the ADC but i can only use 1 MUX to connect all 12 analog input pins to 1 channel of the ADC. Using multiple MUX prior to the ADC results in the following error:

"Net "\ADC:Net_2020\" is connected to analog mux "AMux_1" and analog mux "\ADC:cy_psoc4_sarmux_8\_CYAMUXSIDE_A", but it may connect to only one analog mux when it is an analog mux common connection".

I thought i could use 6 MUX's with 2 inputs each to limit the number of inoput of the adc but thats apparently not possible. Using 1 MUX for all 12 Inputs would work but feels kind of wrong since i am not using the ADC to its full potential. I really hope theres an easy answer to my problem.

Kind Regards,

Christian

 

user_1377889's picture
User
10440 posts

You might think about to use the ADC channels in "Differential"  mode. It looks as if your "Ref" inputs could be used to calculate the difference between Sensor and Ref. This would reduce the number of channels to 6.

Do not use analog muxes, they will not work with the ADC.

 

Bob

That would reduce the number of inputs of the adc but I lose a lot of functionality. I need the absolute Value of the "Ref" inputs. I know their chracteritics and with their analog value I can determine important parameters. That's why I cant use differential channels.

vsrs's picture
Cypress Employee
101 posts

Hi Christian,

PSoC 4200M supports 8 dedicated pins from SAR Mux, 2 pins through the analog mux bus, and 4 from opamp pins. So one thing you can do is as you are not using any opamps, use four of them in follower mode and connect them to the ADC. This will avoid the routing problem and you can give 12 input signals. I have attached your project after editing, now there is no routing problem.

Regards,

vsrs

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