Other Parts Discussed in Thread: USB2ANY
First off, I am not using USB2ANY to control the eval board, I don't have the cable. I am using an FPGA controller (CMOD A7) to connect directly to the CS, SCLK, SDI & SDO pins. I have attached a couple of oscilloscope snapshots of my timing, I apologize for the quality of the pictures, as our oscilloscope doesn't have screen capture. The orange/yellow curve is SCLK, the white curve is SDI, the blue curve is CS, and the green curve is SDO.
The following image shows me trying to write the value 0x8fff to DAC 4, and the second one shows a single bit going high to show what side of SCLK I am writing on. Overall, I'm writing 0x0b 8f ff.
Next, I tried reading the DEVICE ID register, so I sent 0x81 00 00 to the DAC, however what I got back was not what I had expected, as you can see in the next picture. I also tried to read other registers, but the SDO pin had the same value no matter which address I entered.
I ended up leaving the SDO trace on the oscilloscope and tried to write to the DAC again, and it was jittering around two or three different values, which was surprising. I have attached one such state.
From my understanding of the default values, even if I don't initialize registers myself, I should be able to write to a DAC, is this correct? Currently, I'm guessing that I'm not writing to any of the registers, but I am getting some kind of response from the SDO pin, so I'm not sure about that.
If you see any obvious timing problems, or things I am writing incorrectly, please let me know. I am powering both VDD and VIO with 3.3V from the FPGA. If you need any additional information from me, or want me to try something out, feel free to tell me.