cbarberis
Joined: 01 Oct 2003
Posts: 172
Location: Punta Gorda, Florida USA
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| Driver for LTC2420 Delta Sigma ADC |
 Posted: Mon Jul 06, 2009 6:17 pm |
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| Code: | /*********************************************************
*
* LTC2420.c
* Driver for LTC2420, SPI 20 bit Delta-Sigma A/D converter
* Compiled for CCS compiler V4 and up
*
* C. Barberis
* Bartek Technologies
*
* Includes: None
*
**********************************************************
*
*
**********************************************************
**********************************************************
* Notes:
* Make sure to drive pin #8 with logic level from cpu, this pin controls internal filter
* for line rejection; Vcc = 50Hz and 0V = 60Hz
* Declare the appropiate I/O pin declarations for: FiltSel,ADCSEL,SDI,SDO and SCK before compiling this file
* Make sure to call (once) ExtAdcInit(); prior to reading adc values.
*********************************************************/
//Function prototypes
void ExtAdcInit(void);
unsigned int32 ReadAdcValue(void);
static short int AdcUnderFlow ;
static short int AdcOverFlow;
union { unsigned int32 AdcCode;
struct {unsigned int8 AdcByte0;
unsigned int8 AdcByte1;
unsigned int8 AdcByte2;
unsigned int8 AdcByte3;}AdcBytes; }AdcValue;
/////////////////////////////////////////////////////////////////////////////////
void ExtAdcInit() // Initialize LTC2420
{
setup_spi(TRUE);
setup_spi(SPI_MASTER|SPI_MODE_0_0|SPI_CLK_DIV_16|SPI_SS_DISABLED); // change spi to low to high sense
output_high(ADCSEL);
FiltSel = 0; // set for 60Hz filtering
//FiltSel = 1; // set for 50Hz filtering
}
/////////////////////////////////////////////////////////////////////////////////
unsigned int32 ReadAdcValue() // Read LTC2420, SPI 20 bit Delta-Sigma ADC
{
AdcValue.AdcBytes.AdcByte3 = 0; // highest byte of the 32 bit int is set to 0
AdcUnderFlow = FALSE;
AdcOverFlow = FALSE;
output_low(ADCSEL); // bring ADCSEL line low to start conversion
while(input(SDI)) // Test for SDI low ready to start conversion
restart_wdt();
delay_us(500); // Start conversions after 500 uS delay
AdcValue.AdcBytes.AdcByte2 = spi_read(0); // read MSB, bits 23 to 16
delay_us(10); // wait 10 uS before next byte read
AdcValue.AdcBytes.AdcByte1 = spi_read(0); // read bits 15 to 8
delay_us(10); // wait 10 uS before next byte read
AdcValue.AdcBytes.AdcByte0 = spi_read(0); // read bits 7 to 0
delay_us(10); // wait 10 uS before we raise ADCSEL chip enable
output_high(ADCSEL); // bring ADCSEL line high to after end of conversion
if( !bit_test(AdcValue.AdcBytes.AdcByte2,5)) // check to see if sign bit shows negative conversion
AdcUnderFlow = TRUE; // if so send underflow error
if( bit_test(AdcValue.AdcBytes.AdcByte2,4)) // check to see if extended range bit shows overflow condition
AdcOverFlow = TRUE; // if so send overflow error
if( bit_test(AdcValue.AdcBytes.AdcByte2,5) && !bit_test (AdcValue.AdcBytes.AdcByte2,4) ) // if everything is ok the mask data
AdcValue.AdcBytes.AdcByte2&=0x0F;
if(AdcUnderFlow) AdcValue = 0; // if we detect an underrange contion return a zero value
return(AdcValue.AdcCode);
}
/////////////////// End of File ///////////////////////////////////////// |
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