Hi, Chris,
I attached AVDD and REFIN+ to DVDD (5V). Also, AGND and REFIN- to DGND.
I'm using PIC but I'm directly controlling SPI signals with GPIO. As you can see the oscilloscope signals, I don't think there is a problem with uC. The uC follows SPI protocol. the uC is programmed to update the signal with the rising edge of the clock.
I tried to set mode register as 0x2130 every 2 seconds. In 1 second after the setting, I read the mode register again, but it is still 0x0140. I attached the setting procedure.
Also, according to the oscilloscope signal, AD7730 returns 0x0140. So, I don't think there is a problem with the uC.
By the way, I send SCLK and DIN with 3.3V high. Do you think it can be a problem?
Thank you,
Kwan Suk Kim