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OJ
Guest
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| Help AD7705 @ 1MHz with 1.225 REF |
 Posted: Mon Apr 21, 2008 2:05 pm |
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Can someone please help I modified the AD7705 driver with the following:
I am using a PIC18F87J60 @ 25MHz. A MIC1555 is the master clock set @ a frequency of 1MHz and a voltage reference at 1.225V.
I turned off the MCLK out by writing 0x10 as the rate, have reset tied high and DRDY is not connected.
Whats happening is I read the same value no matter what is on the input.
I checked the master clock and it is generating 1MHz. I have 5 boards and I get the same result.
Thanks in advance.
the ADC should be setup unipolar,gain=1,cal=normal rate=20hz
| Code: |
#define ADC_DO PIN_D0
#define ADC_DI PIN_D1
#define ADC_CLK PIN_D2
#define ADC_CS PIN_H2
#define OSC_CS PIN_H0 //MIC1555 enable
//Calibration
//#define ADC_NORMAL 0
//#define ADC_SELF 64
//#define ADC_ZERO_SCALE 128
//#define ADC_FULL_SCALE 192
//Gain
//#define ADC_GAIN_1 0
//#define ADC_GAIN_2 8
//#define ADC_GAIN_4 16
//#define ADC_GAIN_8 24
//#define ADC_GAIN_16 32
//#define ADC_GAIN_32 40
//#define ADC_GAIN_64 48
//#define ADC_GAIN_128 56
//Polarity
//#define ADC_BIPOLAR 0
//#define ADC_UNIPOLAR 4
//Rates
//#define ADC_20 16
//#define ADC_25 17
//#define ADC_100 18
//#define ADC_200 19
/********************Convert ADC Value To Volts ********************************/
float ToVolts(long data)
{
return ((float)data*1.225/0xffff);
}
/******************** Write To ADC *********************************************/
void write_adc_byte(int data)
{
int i;
output_low(ADC_CS);
for(i=0;i<8;i++)
{
output_low(ADC_CLK);
output_bit(ADC_DI, shift_left(&data,1,0));
output_high(ADC_CLK);
}
output_high(ADC_CS);
}
/******************** Disable ADC **********************************************/
void adc_disable(void)
{
write_adc_byte(0x04);//Place in standby mode
output_low(OSC_CS);//Turn Off Oscillator
}
/******************** Enable ADC **********************************************/
void adc_enable(void)
{
output_high(OSC_CS);//Turn On Oscillator
write_adc_byte(0x00);
}
/******************** Read Value From ADC **************************************/
long read_adc_word(void)
{
int i;
long data;
output_low(ADC_CS);
for(i=0;i<16;i++)
{
output_low(ADC_CLK);
output_high(ADC_CLK);
shift_left(&data,2,input(ADC_DO));
}
output_high(ADC_CS);
return data;
}
/******************** Setup ADC **************************************/
void setup(void)
{
write_adc_byte(0x20);
write_adc_byte(0x10);
write_adc_byte(0x10);
write_adc_byte(0x04);
}
/******************** Initialize ADC *******************************************/
void init_ADC(void)
{
output_high(OSC_CS);
output_high(ADC_CLK);
output_high(ADC_CS);
setup();
delay_ms(3000);
}
/******************** Read ADC Value From Specified Channel ********************/
long read_adc_value(int1 ch)
{
long value;
if(ch){write_adc_byte(0x39);}
else{write_adc_byte(0x38);}
//value=/*ToVolts(*/read_adc_word();//);;
return value;
}
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here is the main routine
| Code: |
void main()
{
init_ADC();
while(TRUE)
{
printf("RAW=%Lu\r",read_adc_value(0));
}
}
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Ttelmah
Guest
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| Posted: Mon Apr 21, 2008 3:28 pm |
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What you have posted, has the entire actual 'reading' code remarked out. 'value', will just contain a random value, dependant on what happened to be in the chip's memory when it turned on....
Best Wishes |
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