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ADC problem | Cypress Semiconductor

ADC problem

Summary: 28 Replies, Latest post by danaaknight on 26 Nov 2012 02:38 PM PST
Verified Answers: 18
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vgy
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137 posts

 Hi to all,

              I am  doing work on blood glucose measurement with PSoC 3 , in that a current from test strip taken and converted to voltage and calibration if that interms of glucose.but as a sample i am giving current from IDAC component that is converted to voltage. this voltage i am giving to ADC to display it in volts , here upto PGA i am getting voltage but after giving to ADC i am getting Garbage value output on LCD.i think the problem here is with ADC ,can anyone help me regarding this.

thanks

PRP

hli
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2575 posts

To make sure it really is an ADC problem, some debug ideas:

  • debug your code to see what you get as a result from the ADC (your LCD write code might also be wrong)
  • use an external value as ADC input to check that it is working correctly
  • route the connection between IDAC and ADC to an external pin and measure the voltage there
vgy
user_214919094's picture
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137 posts

 Hi Sir,

          Upto PGA working and ADC also working properly individualy but when i am cascading both,i am not getting anything .

Thanks 

PRP

user_1377889's picture
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9581 posts

Route the output of the PGA to a pin to observe it is within the input-range of the ADC, watch it with oscilloscope.

 

Bob

vgy
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137 posts

i Did that i got output from PGA with 4v and my ADC input range is 0 to Vdd which is 5v but still i am facing problem

user_1377889's picture
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9581 posts

There are some critical settings with ADC, can you post at least the settings of the ADC when not the complete zipped project.

 

Bob

vgy
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137 posts
vgy
user_214919094's picture
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137 posts

 i am unable to upload the project what to do ?

vgy
user_214919094's picture
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137 posts
hli
user_78878863's picture
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2575 posts

When I open this project with Creation 2.1, it complains about outdated devices to be used. Do you use a PSoC3 Engineering Silicon? If yes, which one?

Can you update to the newest version of creator?

hli
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2575 posts

One thing to note in your project is that the TIA output can get negative when the IDAC writes to the full values (31.875µA * 40kOhm gives 1.28V which is way larger than the reference voltage).

Also, is there a reason why you read the ADC result 4 times, and discard the first 3 readings?

Btw: since you don't change the IDAC - what is the result you see on the LCD? When I calculated correctly, it should 1.4V (4*(0.4-1.5µA*40kOhm), and it should be stable.

 

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