ADC PROBLEM - MC908SQG4

Cram — Thu, 19 Mar 2009 17:55:28 GMT

Hi,

I'm using the MC908SQG4 (pdip 8 pins) for adquire two volatge levels using the ADC module. I don't need and interruption during the normal opreration so I decide to use a polling software solution, and here begins the problem. I'm just debbuging some test code just to verify the adquisition method, and when I start the conversion as soon as i choose the input channel the COCO flag is set to 1, and finish the conversion process without result (ok result equals 0) here is the code

ADC configuration:

void initCAD(){

    //0001 1000
    ADCCFG_ADICLK=0;
    ADCCFG_MODE=2; //10 --> 10 bits
    ADCCFG_ADLSMP=1;
    ADCCFG_ADIV=0;
    ADCCFG_ADLPC=0;

    ADCSC2=0x00;

    //0001 1111
    ADCSC1_ADCH=0x1F;
    ADCSC1_ADCO=0;
    ADCSC1_AIEN=0;

    //0000 0011 PTAD0+PTAD1

    APCTL1=0x03;
}

main loop:

for(; {

    delay1ms();

    ADCSC1_ADCH=0x01;   --> here I select CH0 or CH1    and COCO flag is SET
    while (!ADCSC1_COCO) ;

    ADCSC1_ADCH=0x1F; --> disable de ADC module
    resL=ADCRL;
    resH=ADCRH;

} /* loop forever */

Anybody can help me? I miss something but I'm not abble to find it!

Thx for all,

Added p/n to subject.

Message Edited by NLFSJ on 2009-03-19 12:36 PM

Re: ADC PROBLEM

bigmac — Fri, 20 Mar 2009 00:55:51 GMT

Hello,

Try reading the ADC result prior to disabling the ADC module. Actually, there is no reason to disable the ADC module since the module will automatically revert to low power mode once each conversion is complete.

Regards,

Mac

topic ADC PROBLEM - MC908SQG4 in 8-bit Microcontrollers

ADC PROBLEM - MC908SQG4

Re: ADC PROBLEM