I am having difficulty communicating with ADF4382A on its eval board using SPI 4 wire mode, or even 3 wire mode in 3.3V setting (CMOS_OV). The only configuration that works is 3 wire mode in 1.8V setting.
If I try and use 3 wire mode in 3.3V setting, or 4-wire mode, the data that I get back does not agree with what's written to the scratch register 0x0A, or read-only register 0x0C 0x0D.
I use oscilloscope to capture what's going through the SPI lines. In 3 wire 1.8V mode, I can see the correct data, for example, 0x0C register will return 0x56 as expected. But in 3.3V 3-wire mode or 4-wire SPI mode, the waveform shows inconsistent data, sometimes 0x01, sometimes 0x07 or simply 0, if I try to read the read-only register 0x0C. Similar inconsistencies if I try other registers or the scratch register 0x0A.
I wonder if this issue is similar to that of ADF4368's eval board that someone had question with: SPI Communication with the ADF4368. 4-wire mode not working
Any ideas?
Thanks.