I am working with an F28377S LaunchPad and a DAC7760 over an SPI connection. My understanding is that the DAC8760 and DACx750 series are very similar in functionality and methodology, so those anyone with experience with those might also be helpful. I have the USB dongle attachment for the DAC7760, so I captured a waveform that was writing the DAC data register so that I could compare my signal with the one I knew was working. Below is the capture from the TI dongle to the DAC.
I also captured my own signal from my F28377S to compare. They appear functionally identical to me. The only possible difference I can think of is that my signal's MOSI isn't far enough ahead of the rising edge of the clock for the DAC to properly shift in the signal.
Is the rising edge switch on the MOSI possibly an issue here? How might I adjust it so that the signal does lead the clock?
More detail on the captures/DAC:
1. The DAC uses 24 bits. 8 bits make up the opcode and the next 16 bits make up the data sent. Optionally there is a 32 bit version with an 8 bit CRC at the end of the burst. I have disabled the CRC mode via the DAC7760 PC application from TI over the dongle.
2. The captures are made up of clock (D0/D4), MOSI (D1/D5), MISO (D2/D6) and chip select / latch (D3/D7).
3. I am verifying that the signal is being programmed through use of the DAC7760 PC application.
Does anyone have any ideas why my SPI signal doesn't seem to have any effect and maybe some steps to take to fix it? I appreciate any pointers, thanks!
Edit: I have changed the clock phase so that we might set the data high before the clock causes the bits to be latched in. I have not yet been able to test this because the module seems to be having an issue with communicating with TI's app now.
Edit 2: See accepted answer for details as to what solved the problem. In short the issue I suspected was the problem. Switching clock phase to allow earlier switching fixed the first issue.
