Actually, this is a continuation of a previous question: Controlling ADF4355 via Arduino. But I think there is no need to read all that to answer my questions below.
First, I will explain my problem. I'm trying to control my ADF4355 evaluation board through SPI using an Arduino and I am still not able to. To be more exact, I have managed to change the output frequencies three ou four times, but the other many times I tested it didn't work.
The strange thing, is when I managed to make it work, after some time it wouldn't work even if I didn't change anything. One curiousity is that it worked when I was making some analysis with the oscilloscope. But right now I'm not being to communicate again even using this "trick".
My SPI communication has the following setup:
Arduino Mega [5.0 V] --> Voltage Logic Level Converter --> ADF4355 [3.3 V]
Pin 52 (SCK) --> 5.0 V to 3.3 V --> TP3 (CLK)
Pin 51 (MOSI) --> 5.0 V to 3.3 V --> TP4 (DATA)
Pin 53 (SS) --> 5.0 V to 3.3 V --> TP5 (LE)
One strange thing is that when the ADF4355 is not connected to the voltage converter, I get higher voltage in the output of the voltage converter. The signal also get noisier when the ADF4355 is connected. We can see this behavior in the photos below. I say that it is strange because I also did some tests using a ADF4106 evaluation board and I didn't notice much of this noise or voltage reduction (I had no problems using ADF4106).
In the beginning I thought it wasn't working because of the low voltage of the SPI communication. I tried rising a little, but I got afraid since there were some spikes that were exceeding the CMOS voltage limit (I have already damaged one ADF4355).
Input of Voltage Converter, CLK and DATA, with ADF4355 Connected
Input of Voltage Converter, CLK and DATA, with ADF4355 NOT Connected
Output of Voltage Converter, CLK and DATA, with ADF4355 Connected
Output of Voltage Converter, CLK and DATA, with ADF4355 NOT Connected
Ok, I think I explained everything. Now, my questions are:
- Is the connection between Arduino and ADF4355 correct? Is there another proper way to connect them? Is there an application note for using SPI communication?
- Is the noise and the voltage reduction common occurences using ADF4355?
- I have noticed that the spikes of the signal are almost at the CMOS voltage limit. Is it safe to try using a higher voltage?
I will gladly accept any suggestions. Thank you very much.