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driver for ADS8317 ADS8320 and related 16Bit AD conversion

 
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asmboy



Joined: 20 Nov 2007
Posts: 2128
Location: albany ny

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driver for ADS8317 ADS8320 and related 16Bit AD conversion
PostPosted: Sat Jun 05, 2010 7:09 pm     Reply with quote

Code:

//
//   generic driver for ADS83xx serial 16 bit A/D converters
//   inc ADS8317, ADS8320,   x18, x21  and many other 8 pin similar parts
//   both signed 16bit and unsigned types
//    Don Person   agw1@nycap.rr.com  GentleWind Inc.
//
//   define your control pins here - 3 are required
#define ADCstart  PIN_E0    //       
#define ADCdata   PIN_E1    //
#define ADCclock  PIN_E2    //
//     if using fast_io for E    ( suggested - I do ) then set_tris_E(0b11111010)
//     NB: this assumes you are using a WEAK resistor pullup on
//        the designated  ADCdata  PIC port pin - even if an external resistor to Vcc
//   
//   This gets one sample 16 bit unsigned word from serial A/D
//

unsigned int16  ADS83xx(void){  // SERIAL A/D  ADS8317,20 and many others
     unsigned int16 adcresult=0;
     unsigned int8 i;
     adcresult=0;
     output_HIGH(ADCclock);      delay_cycles(4);
    //        Start a conversion with a lo pulse on ADC_CONVERT
    output_low (ADCstart); // LOWER NOT-CS
   //                    NOW CYCLE TILL WE GET THE ACTIVE FIRST BIT ZERO READY
   //                    ADCclock is clock DEFLT LOW
   delay_cycles(1);     // not  needed on master clock speed s below 10 mhz
   output_LOW(ADCclock); //  clock low
   delay_cycles(1);     // not  needed on master clock speed s below 10 mhz

   for ( i = 0 ; i < 8 ; i++ ){
     output_HIGH(ADCclock);   
     IF ( !input(ADCdata)) BREAK;
     ELSE output_LOW(ADCclock);
   }
   output_low(ADCclock);   // insure lo clock for a 'break'  on HI state
   //                                           now read data
  for (i=0;i<16;i++){
     output_high(ADCclock);        //    now after rising edge
     adcresult |= input(ADCdata); //   OR input pin with 16bit int
     output_low(ADCclock);   // produce a new lo-to-high clock
     if (i !=15) adcresult=adcresult<<1;         // and shift that bit along toward MSB
  }
  //    leave ready for the  next A/D  read CYCLE
   OUTPUT_HIGH(ADCstart); // adcstart SHUT OFF CONVERTER
  return (ADCresult);
}

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