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AD7714 Driver Help!!

 
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bloureiro



Joined: 26 Feb 2007
Posts: 6

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AD7714 Driver Help!!
PostPosted: Wed Mar 07, 2007 6:26 am     Reply with quote
Hi

I'm trying make the driver for AD7714, I've two problems.
The driver is working the basic.

The i can read the channels but i try read the channel 2 the adc send-me the value of channel 1.
The another problem is when I try read some channel I need use self-calibration first and then read the value.

the self-calibration put the program slow.

Code:

//*************************************************************
// Driver routines for the AD7714 chip, by ToHu
// write_adc_byte()
// adc_init()
// read_adc_word()
// read_adc_value()
//*************************************************************

//connection pins to the PIC
#define ADC_DRDY  PIN_B1
#define ADC_DO    PIN_B2
#define ADC_DI    PIN_B3
#define ADC_RESET PIN_B4
#define ADC_CS    PIN_B5
#define ADC_CLK   PIN_B6

void write_adc_byte(int data)
{
   int i;
   output_low(ADC_CS);
   for(i=1;i<=8;++i)
   {
      output_low(ADC_CLK);
      output_bit(ADC_DI, shift_left(&data,1,0));
      output_high(ADC_CLK);
   }
   output_high(ADC_CS);
}

adc_init()
{
   output_low(ADC_RESET);
   output_high(ADC_CLK);
   output_high(ADC_CS); //Set low to AD7714 chip select low pin
   output_high(ADC_RESET); //Set high to AD7714 reset low pin
   delay_ms(2000);
   write_adc_byte(0x27); //to com.register, chanel & filter Hi  antes 24----27 datacheat
   write_adc_byte(0xC0); //to filter hi register  0xCF gasta menos do sinal analogico  4F data cheat
   write_adc_byte(0x37); //to com.register, chanel & filter low  antes 30       37  data cheat
   write_adc_byte(0x13); //to filter low register  00 antes-------------------------------A0 data cheat
   write_adc_byte(0x17); //to com register, chanel & mod register               17 data cheat
   write_adc_byte(0x20); //to mod register, self test---------------------------20
}



int32 read_adc_word()
{
   int i;
   int32 data;
   output_low(ADC_CS);
   for(i=1;i<=24;++i)
   {
      output_low(ADC_CLK);
      output_high(ADC_CLK);
      shift_left(&data,3,input(ADC_DO));
   }
   output_high(ADC_CS);
   return data;
}



int32 read_adc_value(int canal)
{
   int32 value;
   //while ( input(ADC_DRDY) );
   //while ( !input(ADC_DRDY) );
   while ( input(ADC_DRDY) ); // Loop until data is ready

   switch(canal)
   {
      case 1:
      write_adc_byte(0x10); //to com register, chanel & mod register
      write_adc_byte(0x20); //to mod register, self test
      write_adc_byte(0x58);//communications register set to read AIN1
      break;

      case 2:
      write_adc_byte(0x11); //to com register, chanel & mod register
      write_adc_byte(0x20); //to mod register, self test
      write_adc_byte(0x59);//communications register set to read AIN2
      break;

      case 3:
      write_adc_byte(0x12); //to com register, chanel & mod register
      write_adc_byte(0x20); //to mod register, self test
      write_adc_byte(0x5A);break;

      case 4:
      write_adc_byte(0x13); //to com register, chanel & mod register
      write_adc_byte(0x20); //to mod register, self test
      write_adc_byte(0x5B);break;

      case 5:
      write_adc_byte(0x16); //to com register, chanel & mod register
      write_adc_byte(0x20); //to mod register, self test
      write_adc_byte(0x5E);break;
   }
   value=read_adc_word();

   return value;
}

float convert_to_volts(int32 temp){
   return (float)temp*0.000000149;
}


Thanks
Humberto



Joined: 08 Sep 2003
Posts: 1215
Location: Buenos Aires, La Reina del Plata

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PostPosted: Wed Mar 07, 2007 8:57 am     Reply with quote
Quote:

The i can read the channels but i try read the channel 2 the adc send-me the value of channel 1.


The AD is performing according to the code.
In the switch statement, you are consulting the Ch2 but addressing Ch1
(0x11 should be 0x12)
Code:

      case 2:
      write_adc_byte(0x11); //to com register, chanel & mod register


You should load the communication register outside of the switch statement
with the value 0x0F/0x6F and then polling waiting that RDY become true, then you
can read each input channel inside the switch()

Humberto
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