topic Re: Kinetis ADC usage issue in Kinetis Microcontrollers

Kinetis ADC usage issue

alvenwu — Tue, 01 May 2018 07:11:30 GMT

I try to use the ADC conversion function on the Kinetis, basically there are two steps , 1. ADC initialization 2 Start a ADC conversion. I use the interrupt mode , which means after the conversion completion , ADC should raise a interrupt , then the program tries to get the conversion data from the ADC data register. Is that process right ? Here is two questions:

1. should the cpu pins involved ADC device be configured at first during the initialization phase.

2. there are two modes , query and interrupt mode to indicate the conversion completion , but when I set the interrupt enable , and start the conversion , however , seems the interrupt is lost, what kind of problem would cause it ?

Here the source code of ADC module:

1. initialization:

static int adc_setup(FAR struct adc_lowerhalf_s *dev)
{
   uint32_t regval = 0;
        FAR struct kinetis_adc_s *pt_Adcdev = (FAR struct kinetis_adc_s *)dev;

   DEBUGASSERT(NULL != pt_Adcdev);

        /* config the sim clock rate*/
        adc_simclock();

        /* CFG config the adc clock to get the ADCK, and select sample time and low-power   */
        regval = ADC_CFG1_ADLPC | ADC_CFG1_ADICLK_BUSCLK | ADC_CFG1_ADIV_DIV5
                     | ADC_CFG1_ADLSMP | ADC_CFG1_MODE_1011BIT;
        adc_putreg(pt_Adcdev, KINETIS_ADC_CFG1_OFFSET, regval);

        /* SC2 select the trigger :software */
        regval = ADC_SC2_REFSEL_ALT;
        adc_putreg(pt_Adcdev, KINETIS_ADC_SC2_OFFSET, regval);

        /* SC3 select hardware averaging*/
        regval = ADC_SC3_AVGS_32SMPLS | ADC_SC3_AVGE;
        adc_putreg(pt_Adcdev, KINETIS_ADC_SC3_OFFSET, regval);

         /* calibrate ADC */
        if (FALSE == adc_alibration(pt_Adcdev))
        {
       return -EINVAL;
   }

return OK;
}

2. start the conversion

static void adc_start(FAR struct adc_lowerhalf_s *dev, FAR char cChannelid)
{
   uint32_t regval = 0;
   FAR struct kinetis_adc_s *pt_Adcdev = (FAR struct kinetis_adc_s *)dev;
        DEBUGASSERT(NULL != pt_Adcdev);

        /*choose a channel*/
   regval = ((cChannelid << ADC_SC1_ADCH_SHIFT) & ADC_SC1_ADCH_MASK) | ADC_SC1_AIEN;

        printf("adc start!\n");

/*start a conversion*/
adc_putreg(pt_Adcdev, KINETIS_ADC_SC1A_OFFSET, regval);
}

Re: Kinetis ADC usage issue

mjbcswitzerland — Tue, 01 May 2018 11:30:46 GMT

Hi Alven

>> should the cpu pins involved ADC device be configured at first during the initialization phase.
This depends on the device and the ADC being used. Dedicated ADC inputs need no initialisation but if a pin with ADC multiplexed with other functions is involved it may require it.

>> seems the interrupt is lost
Do you enable the ADC interrupt in the NVIC?

Regards

Mark

P.S. Don't forget to calibrate the ADC before first use!

uTasker developer and supporter (+5'000 hours experience on +60 Kinetis derivatives in +80 product developments)
Kinetis: http://www.utasker.com/kinetis.html

Re: Kinetis ADC usage issue

Robin_Shen — Tue, 08 May 2018 03:06:31 GMT

Q1. should the cpu pins involved ADC device be configured at first during the initialization phase.
A1 The pins with analog functions assigned to them default to their analog function after reset. So you don't need to configure PORTx_PCRn[MUX] select the pin as ADC input function.

Q2. there are two modes , query and interrupt mode to indicate the conversion completion , but when I set the interrupt enable , and start the conversion , however , seems the interrupt is lost, what kind of problem would cause it ?
A2 I agree with Mark. Seems that you forget enable ADC interrupt in NVIC.

I recommend you refer the ADC examples in MCUXpresso SDK.

First Search MCU and Build MCUXpresso SDK.

Then Download SDK

Best Regards,

Robin

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