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ppmc_dac.c

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//ppmc dac functions

#include "ppmc.h"


/*
VoltToCount(double volts)  converts a voltage to a
number of counts to output to the dac

  output to DAC word works like:

  0xFFFF -> +10 V
  0x8000 ->   0 V
  0x0000 -> -10 V
  */


__inline unsigned short VoltToCounts(double volts)
{
        long nCounts;
        nCounts = (long) (((volts / 10.0) * 0x7FFF)+0x8000);

        if (nCounts > 0xffff)
    {
      nCounts = 0xffff;
    }
        if (nCounts < 0 )
    {
      nCounts = 0;
    }
        return (unsigned short)nCounts;
}

int RawDAC(int nAxis, double volts)
{
  

  if ( (nAxis > PPMC_MAX_AXIS) || (nAxis < 0) )        /* is axis within range? */
    return -1;

  /* convert -10.0 -> 0,0 to 0x8000 10 -> 0xFFFF */
  
  if (nAxis <=3)
   {
    SelWrt16(DAC_0 + (nAxis << 1), VoltToCounts(volts));
        SelWrt(DAC_WRITE_0, 0);
   }
  else {
    SelWrt16(DAC_4 + ((nAxis-4) << 1), VoltToCounts(volts));
        SelWrt(DAC_WRITE_1, 0);
  }
        
        
  return 0;
}

short DACInit(void)
{
        SelWrt(DAC_WRITE_0,0);    // reset strobe
        SelWrt(DAC_MODE_0,0);     // sel strobe to INTR/ line
        return 0;
}

short DACQuit(void)
{
           return DACInit();  //init sets all outputs to zero
}
int ppmcDacNum(void)
{
        return PPMC_MAX_AXIS;
}

int ppmcDacWrite(int dac, double volts)
{
  return RawDAC(dac, volts);
}

int ppmcDacWriteAll(int max, double * volts)
{
        int t;
  int smax;
 
  /* clip smax to max supported-- if they want more, ignore */
  if (max > PPMC_MAX_AXIS) {
    smax = PPMC_MAX_AXIS;
  }
  else {
    smax = max;
  }
#ifndef PPMC_8_AXIS
  //take advantage of auto increment of address pointer in ppmc
        SelAddr(DAC_0);
        for (t = 0; t < smax; t++)
        {
  /*      printf(" dac channel %d volts %12.4f   digital # %d\n",
          t,volts[t],VoltToCounts(volts[t]));  */
                WriteData16(VoltToCounts(volts[t]));
    }
        /*      printf("\n");  */
#else
        SelAddr(DAC_0);
        if(smax<=4)
        {
           for (t = 0; t < smax; t++)
             {
                WriteData16(VoltToCounts(volts[t]));
             }
           return 0;
        }
        else
        {
          for (t = 0; t < 4; t++)
            {
              WriteData16(VoltToCounts(volts[t]));
            }
          SelAddr(DAC_1);
          for (t = 4; t < smax; t++)
            {
                WriteData16(VoltToCounts(volts[t]));
            }
    }
#endif
  return 0;
}

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