I'm having some trouble with getting a DAC8531 going. I am prototyping a new board so right now I have the DAC on a surfboard pulgged into a breadboard with flying wires over to an Analog Devices ADUC7026 eval board via SPI. Everything is on 3.3V including the Vref pin on the DAV
The issue is that values 0x0000 to 0x7FFF map to 0% to 25% of Vref on the output and values 0x8000 to 0xFFFF map to 75% to 100% of Vref. That is, no input will result in output values between 25% and 75% of Vref.
I have illustrated this by writing a little program to input a sawtooth curve with a period of ~20 seconds and then looking at the output on a scope. I have included that trace.
I have also included a schematic of my test setup and a scope trace of the digital input to the DAC (ch1 -> SCLK, ch2 -> MOSI, ch3 -> CS). The value being written to the DAC during this trace is 0x7FFF.
