DAC7612 Digital to Analog converter, only 11 bit resolution

K de Jong

Hi all,

I have built a prototype with the DAC7612 DA converter.

The datasheet specifies 12 bit resolution, =4096 steps from 0 to 4.095 Volts (1 mVolt each). But I only get out 2048 steps = 2 mVolt for each step.

Below is the routine I use. I have to devide my variable OutDAC by two because of the resolution problem.

WriteDAC:
HIGH LOADDACS
LOW CSDAC
SHIFTOUT Dout,Sclk,MSBFIRST,[noparse][[/noparse]ChDAC\2,(OutDAC/2)\11]
HIGH CSDAC
LOW LOADDACS
RETURN

Also a graph of the DAC output versus time is atached.

Does anybody have a good idea where to find the missing bit ??

Thanks in advance,

Klaus

Newzed

Klaus, try writing:

SHIFTOUT Dout,Sclk,MSBFIRST,[noparse][[/noparse]ChDAC\2,(OutDAC/2)\12]

Sid

K de Jong

And this code goes first, Of course )))))))))).

OutDAC VAR Word
ChDAC VAR Nib
OutDAC=0
ChDAC=2

DO
IF OutDAC>4095 THEN OutDAC=0
OutDAC=OutDAC+2
ChDAC=2
IF OutDAC>4095 THEN OutDAC=0
OutDAC=OutDAC+2

ChDAC=2
GOSUB WriteDAC

ChDAC=3
OutDAC=OutDAC-500
GOSUB WriteDAC
OutDAC=OutDAC+500

PAUSE 200
DEBUG CR,DEC OutDAC

LOOP

Klaus