ADS8689_BCM2835.cpp

/*----------------------------------------------------*\
 * This is a library to interface the ADS8689 ADC chip *
 * with a Raspberry Pi usign BCM2835 library           *
 *                                                     *
 * Author: Marco Duarte                                *
 \----------------------------------------------------*/
 
#include "ADS8689_BCM2835.h"

uint16_t ADS8689::sendCommand(uint8_t op, uint8_t address, uint16_t data)
{
  char buff[4] = {0};
  
  buff[0] = op/*(op | (address >> 7))*/;
  buff[1] = address/*(address << 1)*/;
  buff[2] = (data >> 8);
  buff[3] = data;
  
  //printf("Sending: %.2x %.2x %.2x %.2x\n", buff[0], buff[1], buff[2], buff[3]);
  
  if(spiModule == SPI_AUX)
    bcm2835_aux_spi_transfern(buff, sizeof(buff));
  else
    bcm2835_spi_transfern(buff, sizeof(buff));
    
  //printf("Got: %.2x %.2x %.2x %.2x\n", buff[0], buff[1], buff[2], buff[3]);
    
  return ((buff[0] << 8) | buff[1]); 
}

bool ADS8689::begin(uint8_t spiModule, uint8_t cs)
{
  this->cs = cs;
  this->spiModule = spiModule;
  
  struct timespec delay;
  delay.tv_sec = 1;
  delay.tv_nsec = 10005;
  
  nanosleep(&delay, NULL);
  
  delay.tv_sec = 0;
  
  if(this->spiModule == SPI_AUX)
  {
    uint16_t clockDivider = bcm2835_aux_spi_CalcClockDivider(3125000);
    bcm2835_aux_spi_setClockDivider(clockDivider);
  }
  else if(this->spiModule == SPI_0)
  {
    if(this->cs != BCM2835_SPI_CS0 && this->cs != BCM2835_SPI_CS1)
    {
      printf("Choose BCM2835_SPI_CS0 or BCM2835_SPI_CS1\n");
      return false;
    }
    
    bcm2835_spi_setBitOrder(BCM2835_SPI_BIT_ORDER_MSBFIRST);
    bcm2835_spi_setDataMode(BCM2835_SPI_MODE0);
    bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_128);
    bcm2835_spi_chipSelect(this->cs);
    bcm2835_spi_setChipSelectPolarity(this->cs, LOW);
  }
  else
  {
    printf("Choose SPI_AUX or SPI_0\n");
    return false;
  }
  
  //set adc to use internal VREF and range to 1.25*VREF

  uint16_t got = 0;
  
  do
  {
    sendCommand(WRITE, RANGE_SEL_REG_7_0, 0x000B);
    nanosleep(&delay, NULL);
    sendCommand(READ_HWORD, RANGE_SEL_REG_7_0, 0x0000);
    got = sendCommand(NOP, 0x00, 0x0000);
    printf("Got: %.2x %.2x\n", got >> 8, (got & 0x00FF));
    nanosleep(&delay, NULL);
  }while(got != 0x000B);
  
  sendCommand(NOP, 0x00, 0x0000);
  
  return true;
}

//you will actually get the value of the adc on any command
//but nop makes sure it doesn't execute anything and you just get the value
//it's best to send all configuration commands before sampling
uint16_t ADS8689::readADC()
{
  return sendCommand(NOP, 0x00, 0x0000);
}