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ac34856
Joined: 14 Dec 2009
Posts: 33
Location: Wales
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| AD7715 CCS driver annoying problem |
 Posted: Mon Jan 25, 2010 9:58 am |
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I've been testing the AD7715 which is the last thing I need to complete
a piece of code. This uses the driver supplied by CCS but so far I can
only get the program to output 0x00ff from the ADC.
If anyone has any ideas it would be much appreciated ... so I can get
this finished. Other bits work fine.
All of the signals appear to be correct and present - and the reference
voltage is 2.5V with a pot providing 0 to 2V input. The MCLK input is
1MHz.
As data is read out I am assuming it may be something to do with
the commands to setup the device. I put in a #define CLK_DEL to stretch out the clock and other SPI signals so this can be ignored as its set to
zero.
Compiler is 4.088
| Code: |
//*********************************************************//
// Skeleton program for reading AD7715 using S/W SPI //
//*********************************************************//
#include <18F4620.h>
#device PASS_STRINGS=IN_RAM
#fuses HS, NOWDT, NOPROTECT, NOBROWNOUT, NOPUT, NOLVP
#use DELAY(CLOCK=20000000) // , OSC=10000000)
#use RS232(BAUD=115200, PARITY=N, XMIT=PIN_C0, BITS=8, ERRORS, RESTART_WDT, STREAM=COM1)
//#use SPI(MASTER, DO=PIN_C5, DI=PIN_C4, CLK=PIN_C3,
// MSB_FIRST, MODE=0, BITS=16, STREAM=SPI_0)
#define LED PIN_D0
#define ADC_CS PIN_B0
#define ADC_RESET PIN_B1
#define ADC_DRDY PIN_B2
#define ADC_CLK PIN_B3
#define ADC_DI PIN_B4
#define ADC_DO PIN_B5
#define CLK_DEL 0 // Number of delay cycles of clock
void adc_init(void);
void write_adc_byte(BYTE);
int16 read_adc_value(void);
int16 read_adc_word(void) ;
int main(void)
{
int16 data = 0;
int16 adval = 0;
int16 count;
fprintf(COM1, "\r\n ** PROGRAM STARTING ** ");
adc_init();
fprintf(COM1, "\r\n ADC Reset (SPI Running !)");
// write_adc_byte(0x3a); // This is normally to access data
while(1)
{ output_toggle(LED);
adval = read_adc_value();
fprintf(COM1, "\r\n %Ld - Version 1.11 ADC Test : %04x", count++, adval);
}
}
void adc_init(void)
{
output_low(ADC_RESET);
delay_ms(500);
output_high(ADC_CLK);
output_high(ADC_CS);
// Set low to AD7715 chip select low pin
output_high(ADC_RESET);
// Set high to AD7715 reset low pin
delay_ms(3000);
write_adc_byte( 0x12 ); // Communications Register
write_adc_byte( 0x62 ); // Setup Register info here
}
void write_adc_byte(BYTE data) {
BYTE i;
output_low(ADC_CS);
delay_us(20);
for(i=1;i<=8;++i)
{ output_low(ADC_CLK);
delay_us(CLK_DEL);
output_bit(ADC_DI, shift_left(&data,1,0));
output_high(ADC_CLK);
delay_us(CLK_DEL);
} output_high(ADC_CS);
}
int16 read_adc_word(void)
{
BYTE i;
long data;
output_low(ADC_CS);
delay_us(CLK_DEL);
for(i=1;i<=16;++i)
{
output_low(ADC_CLK);
delay_us(CLK_DEL);
output_high(ADC_CLK);
delay_us(CLK_DEL);
shift_left(&data, 2, input(ADC_DO));
delay_us(CLK_DEL);
}
delay_us(CLK_DEL);
output_high(ADC_CS);
return(data);
}
int16 read_adc_value()
{
int16 value;
while ( input(ADC_DRDY) );
while ( !input(ADC_DRDY) );
while ( input(ADC_DRDY) );
write_adc_byte(0x3a);
value = read_adc_word();
return(value);
} |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Jan 25, 2010 11:26 am |
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| Quote: | int16 adval = 0;
fprintf(COM1, "\r\n %Ld - Version 1.11 ADC Test : %04x", count++, adval); |
To display an 'int16', you need to use "%lx" in the format string.
(That's a lower case L). |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Mon Jan 25, 2010 12:03 pm |
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| Seems like you're setting a gain of 32 (in communication register) and MCLK of 2.45 MHz (in setup register). |
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ac34856
Joined: 14 Dec 2009
Posts: 33
Location: Wales
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| Posted: Tue Jan 26, 2010 3:45 am |
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Thanks for both comments. It turned out to be something more fundamental and as usual human error - the IC I bought was a 3.3V version, so now I've got the right one its fixed.
As ever always read the small print - |
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