topic ADC on MC9S08 : 8bits; Hight speed; single conversion in 8-bit Microcontrollers

ADC on MC9S08 : 8bits; Hight speed; single conversion

Iko — Thu, 29 Oct 2020 09:49:36 GMT

Hi all i'll try to do this way. Could you confirm that this work?

First, i made an init:

static void adc_init(void)   {#ifndef FAKEDEV   APCTL1 = 0x0F ;  // Desable buffers I/O  for pins:   APCTL2 = 0x8F ;  // ADP 0->3;8->11;15;16->19; et 21->23   APCTL3 = 0xEF ;  // Pin PORT A;B and C   ADCSC2 = 0x00 ;  //raz & config reg SC2 . Start convertion by write on ADCSC1;   ADCCV  = 0x00 ;   //No save of compared value   ADCCFG = 0x00 ;  //Full power (hight speed)                    //Clock divide by 1                    //Standard sampling time (3.5 adc clocks)                    //8 bits operations                    //Bus clk selected   ADCSC1 = 0x1F ;  //Clear Flag conversion Complet (COCO)                    //NO Interrupt                    //Single conversion Mode                    //ADC DISABLE => ADCH = 11111;#endif   }

during my program, i call a simple function with channel parameter "voie"

static U8 adc_lecture(U8 voie)   {   U8 value = 0 ; //U8 is define as unsigned char#ifndef FAKEDEV   ADCSC1 = voie ;   while (! ADCSC1_COCO)      {      ;      }   value = ADCRL;   ADCSC1 = 0x1F ;#endif   return value ;   }

Do you think it's a good way?

ty in advance...

Re: ADC on MC9S08 : 8bits; Hight speed; single conversion

bigmac — Fri, 23 Apr 2010 21:51:25 GMT

Hello,

It is unclear to me why your functions might be "static".

While it will do no harm, the writing of the value 0x1F to ADCSC1 after each conversion is probably unnecessary since the ADC should automatically enter a lower power mode on completion of each conversion.

For your wait loop, the following code would suffice -

while (!ADCSC1_COCO);

Regards,

Mac

Re: ADC on MC9S08 : 8bits; Hight speed; single conversion

Iko — Sun, 25 Apr 2010 04:23:44 GMT

Hi big mac ^^

Ty for this answer.

I hadn't see that it go to low power after each conversion....

In addition, you write "should" (scuse i'm french ^^).

To be sure that it stop, i prefer write 0x1F to disable ADC...

TY ^^