adc.c

// ASF
#include "compiler.h"
#include "delay.h"
#include "interrupt.h"
#include "print_funcs.h"
#include "spi.h"

#include "conf_board.h"
#include "events.h"
#include "types.h"
#include "adc.h"
#include "interrupts.h"

// ad7923 control register
#define AD7923_CTL_WRITE  (1 << 11)
#define AD7923_CTL_SEQ1   (1 << 10)
#define AD7923_CTL_ADD1   (1 << 7)
#define AD7923_CTL_ADD0   (1 << 6)
#define AD7923_CTL_PM1    (1 << 5)
#define AD7923_CTL_PM0    (1 << 4)
#define AD7923_CTL_SEQ0   (1 << 3)
#define AD7923_CTL_RANGE  (1 << 1)
#define AD7923_CTL_CODING (1)

// command word to which we add the desired channel address for conversion
#ifdef MOD_TRILOGY
#define AD7923_CMD_BASE ( AD7923_CTL_WRITE | AD7923_CTL_PM0 | AD7923_CTL_PM1 | AD7923_CTL_CODING)
#endif

#ifdef MOD_TELETYPE
#define AD7923_CMD_BASE ( AD7923_CTL_WRITE | AD7923_CTL_PM0 | AD7923_CTL_PM1 | AD7923_CTL_CODING | AD7923_CTL_RANGE)
#endif

#ifdef MOD_ALEPH
#define AD7923_CMD_BASE \
    (AD7923_CTL_WRITE | AD7923_CTL_PM0 | AD7923_CTL_PM1 | AD7923_CTL_CODING)
#endif


// perform a conversion on all 4 channels
void adc_convert(U16 (*dst)[4]) {
  U16 cmd, val;

  u8 irq_flags = irqs_pause();

  // data into AD7923 is a left-justified 12-bit value in a 16-bit word
  // so, always lshift the command before sending
  cmd = ( AD7923_CMD_BASE ) << 4;
  spi_selectChip(ADC_SPI, ADC_SPI_NPCS);
  spi_write(ADC_SPI, cmd);
  spi_unselectChip(ADC_SPI, ADC_SPI_NPCS);

  // get channel 0, setup channel 1
  cmd = ( AD7923_CMD_BASE | AD7923_CTL_ADD0 ) << 4;
  spi_selectChip(ADC_SPI, ADC_SPI_NPCS);
  spi_write(ADC_SPI, cmd);
  spi_read(ADC_SPI, &val);
  spi_unselectChip(ADC_SPI, ADC_SPI_NPCS);
  (*dst)[0] = val & 0xfff; 

  // get channel 1, setup channel 2
  cmd = ( AD7923_CMD_BASE | AD7923_CTL_ADD1 ) << 4;
  spi_selectChip(ADC_SPI, ADC_SPI_NPCS);
  spi_write(ADC_SPI, cmd);
  spi_read(ADC_SPI, &val);
  spi_unselectChip(ADC_SPI, ADC_SPI_NPCS);
  (*dst)[1] = val & 0xfff;

  // get channel 2, setup channel 3
  cmd = ( AD7923_CMD_BASE | AD7923_CTL_ADD1 | AD7923_CTL_ADD0 ) << 4;
  spi_selectChip(ADC_SPI, ADC_SPI_NPCS);
  spi_write(ADC_SPI, cmd);
  spi_read(ADC_SPI, &val);
  spi_unselectChip(ADC_SPI, ADC_SPI_NPCS);
  (*dst)[2] = val & 0xfff;

  // get channel 3, dummy write
  cmd = ( AD7923_CMD_BASE ) << 4;
  spi_selectChip(ADC_SPI, ADC_SPI_NPCS);
  spi_write(ADC_SPI, cmd);
  spi_read(ADC_SPI, &val);
  spi_unselectChip(ADC_SPI, ADC_SPI_NPCS);
  (*dst)[3] = val & 0xfff;

  irqs_resume(irq_flags);
}

// setup ad7923
void init_adc(void) {
  u16 cmd;

  // at powerup, the part wants a dummy conversion with DIN high
  spi_selectChip(ADC_SPI, ADC_SPI_NPCS);
  spi_write(ADC_SPI, 0xffff);
  spi_unselectChip(ADC_SPI, ADC_SPI_NPCS);

  // wait for powerup time (5us in datasheet)
  delay_us(5);
  
  // write base configuration
  cmd = AD7923_CMD_BASE << 4;
  spi_selectChip(ADC_SPI, ADC_SPI_NPCS );
  spi_write(ADC_SPI, cmd );
  spi_unselectChip(ADC_SPI, ADC_SPI_NPCS );

}