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ADUCM360 ADC voltange range setup

Question asked by Absel on Nov 2, 2017
Latest reply on Nov 9, 2017 by MCollins

Hello,

 

I'm trying to configure the ADC on ADUCM360 in order to read the voltage connected to a PT100 resistor. The input value range goes from about 2V to 3V. This is the code I'm using:

 

 

 AdcGo(pADI_ADC1,ADCMDE_ADCMD_IDLE);     // Place ADC1 in Idle mode
   AdcMski(pADI_ADC1,ADCMSKI_RDY,1);              // Enable ADC ready interrupt source        
   AdcFlt(pADI_ADC1,0,0,FLT_NORMAL|ADCFLT_NOTCH2|ADCFLT_CHOP); // ADC filter set for max update rate with chop on enabled
   AdcRng(pADI_ADC1,ADCCON_ADCREF_AVDDREF,ADCMDE_PGA_G1,ADCCON_ADCCODE_UINT); // avdd reference selected, Gain of 1, truncate negative results to 0
   // Turn off input buffers to ADC and external reference    
   AdcBuf(pADI_ADC1,ADCCFG_EXTBUF_OFF,ADCCON_BUFBYPN|ADCCON_BUFBYPP|ADCCON_BUFPOWP|ADCCON_BUFPOWN);
   AdcPin(pADI_ADC1,ADCCON_ADCCN_AGND,ADCCON_ADCCP_AIN1); // Select AIN1 as postive input and AGND as negative input

 

As you can see the reference selected is AVDD and the ADCCON_ADCCODE is set to UINT (AdcRng function) in order to perform as unipolar (Am I wrong?). I thought this would give me a range from 0 to AVDD and I could read the input data correctly. The thing is that it isn't working.

I'm retreiving the output like this:

 

   fVolts = fVoltage;
   fVolts   = (1.2 / 268435456);      // Internal reference, calculate lsb size in volts
   fVoltage = (ulADC1Result * fVolts);   // Calculate ADC result in volts

 

(I'm using this conversion inside ADC1_Int_Handler function for simplicity).

 

Any help will be really grateful.   

 

EDIT:

 

I changed fVolts to fVolts = (3.3/368435456) and it seems that is working better. Then I change my question to: How can I set this conversion with the exact value of AVDD, as it may vary a little bit around 3.3V am I right?

 

Also, I'm getting an error on ADCSTA register 0x10 from time to time, this is meant to be triggered when there is an outrange error, but I don't know how can I fix it, any ideas?

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