Difficulty setting phase on Si5351 on
Hi, I have written a library for the Arduino that allows control of nearly all of the functions of the Si5351A (without having to use ClockBuilder), however there is one command that I cannot get to work correctly, and that is setting the initial phase.
Allow me to describe my observations. If I take CLK0 and CLK1 and set them to be referenced to PLLA and to be set to the exact same frequency, they will be initialized at a seemingly random phase in reference to each other. However, when I set the CLK0 and CLK1 phase registers to the same phase value (I chose 0 and other values), I observe the exact same behaviors. To illustrate what I see, here are some screen captures from my oscilloscope showing the random initial phase values upon startup. Each time, I just cycled power between screen captures.
AN619 implies, but does not outright state, that the phase registers should be set before setting the MS registers, so I initially did that, but to no avail. I also tried setting the phase registers after setting the MS registers, but that also did not help. I assume there is some specific procedure for setting the phase registers that I am missing, but I cannot find it in AN619. Any help I can get in this area would be greatly appreciated.
Having this capability will allow us to do some neat things with the SI5351, such as using it as a quadrature local oscillator for SDR applications and doing phase modulation like PSK.
Oct 28 2017, 4:42 PM