Hi every body,
I'm using the AD7683 (16 bit A/D converter) and regardless the value of the input voltage, the 4 LSB of the output stay allways in '1111' . The MSB seems to follow the input value, the problem is with the LSB.
Did anyone have a similar trouble? How did you solved?
Thank you
Have you got the REF pin tied to VDD?
Is your input voltage in the range 0 to REF?
Maybe have a look at your SPI output on a CRO (DOUT and trigger with CS). Vary the voltage & see if the LSBs are actually changing...
It may just be that your SPI interface (what you have your SPI lines connected to - microcontroller / FPGA or whatever) is reading the LSBs in the wrong place (ie. in the wrong timeslot).
Cheers,
Anthony Getting Started With Xilinx FPGAs Video Guide
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