So awhile back a friend needed some sample code for using the Arduino to control some SPI TI chips. I wrote the code and tested with my logic analyzer to verify it worked.
Time passed, and friend called and said his code wasn't working and my sample wasn't either. So we hooked it up to his old analog scope and it appeared that the SCLK was behaving as it should, but the MOSI (pin 12) was showing about 0.25V for low and 0.5V for high.
I verified that his probes and scope settings were correct...
We tried several different boards. All showed the same issue.
So I came home and tried my sample code with my scope and got the same issue. I then tried the DIgitalPot example and have the same issue. I have verified that both probes and scope are set to 10X and the same levels. Here is a screen capture from the scope showing the problem.