topic Chip_ADC_StartCalibration in LPC Microcontrollers

Chip_ADC_StartCalibration

vaque — Mon, 27 Mar 2017 10:19:50 GMT

Hi!;

In adc_8xx.c there is a function to calibrate the ADC: Chip_ADC_StartCalibration:

/* Start ADC calibration */
void Chip_ADC_StartCalibration(LPC_ADC_T *pADC)
{
/* Set calibration mode */
pADC->CTRL |= ADC_CR_CALMODEBIT;

/* Clear ASYNC bit */
pADC->CTRL &= ~ADC_CR_ASYNMODE;

/* Setup ADC for about 500KHz (per UM) */
Chip_ADC_SetClockRate(pADC, 500000);

/* Clearn low power bit */
pADC->CTRL &= ~ADC_CR_LPWRMODEBIT;

/* Calibration is only complete when ADC_CR_CALMODEBIT bit has cleared */
}

I am working with a LPC824. Why is firstly the /*Set calibration mode*/?, shouldn't it be last after the 500KHz SetClockRate?.

And other cuestion, what does it mean by ADC_CR_CALMODEBIT? it says in UM10800.pdf at page 327 "21.6.1 ADC Control Register" that the bit 8 (the corresponding of ADC_CR_CALMODEBIT) is reserved.

Thanks so much and regards. Daniel.

Re: Chip_ADC_StartCalibration

kerryzhou — Tue, 28 Mar 2017 07:12:45 GMT

Hi Daniel,

Answer your two questions:

1. Why is firstly the /*Set calibration mode*/?, shouldn't it be last after the 500KHz SetClockRate?.

This is the calibration correct cycle, the chip just design it like this, you can't change the operation sequence.

You can find it from chapter:

2. what does it mean by ADC_CR_CALMODEBIT?

CALMODE it bit 30, you can find it from the user manual:

I think maybe you want to ask ADC_CR_ASYNMODE, it is bit 8, I think it just want to clear these bit.

Wish it helps you!

Have a great day,
Kerry

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Re: Chip_ADC_StartCalibration

vaque — Tue, 28 Mar 2017 10:39:53 GMT

Kerry Zhou thanks so much. You are aright, I wanted to ask about ADC_CR_ASYNMODE...

Thanks a lot! Regards. Daniel.