TMS320F280049: Internal reference configuration

Richard Robinson

Hi ,

I have a design in which I wish to use the internal reference I have the following code to configure Vref to 2.5V:-

ADC_setVREF(ADCA_BASE, ADC_REFERENCE_INTERNAL, ADC_REFERENCE_2_5V);
ADC_setVREF(ADCB_BASE, ADC_REFERENCE_INTERNAL, ADC_REFERENCE_2_5V);
ADC_setVREF(ADCC_BASE, ADC_REFERENCE_INTERNAL, ADC_REFERENCE_2_5V);
//
// Set the DAC gain to 2
//
DAC_setGainMode(DACA_BASE, DAC_GAIN_ONE);

//
// DACREFSEL = 1 VREFHI
//
DAC_setReferenceVoltage(DACA_BASE, DAC_REF_ADC_VREFHI);

//
// Load count value for DAC on next SYSCLK
//
DAC_setLoadMode(DACA_BASE, DAC_LOAD_SYSCLK);

//
// Enable DAC output
//
DAC_enableOutput(DACA_BASE);

however I see no voltage on the VREFHIA/B/C pin. My understanding from the datasheet is that this pin should be driven when the internal reference is selected. The VREFHI pin is connected only to a 2.2uF capacitor and has no external drive source. What am I missing?

Thanks,

Richard.

over 4 years ago

+1 Joseph Casuga over 4 years ago

TI__Mastermind 41750 points

Hi Richard,

You have configured the internal VREF correctly from the above code snippet, however you will not be able to measure the internal VREF unless the ADC is turned on (e.g. with function call ADC_enableConverter(base)).

Best regards,

Joseph

0 Richard Robinson over 4 years ago in reply to Joseph Casuga

Intellectual 740 points

Hi Joseph,

I had actually called ADC_enableConverter elsewhere in the code, but I had only called it for ADCA_BASE. Then it struck me that it would need to be called for A,B and C. Once I called all three the internal reference worked. Thank you for your responce.

Regards,

Richard.

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TMS320F280049: Internal reference configuration