USB-8451 Signal Mapping Issue

[ashrek]

I recently bought a used  USB-8451 to try some Labview SPI/I2C development. I found that when I create a simple Write VI and look at the signals on a PC based logic analyzer I see that the SCLK and MOSI lines are reversed. I verified that I have the correct connections going to the analyzer and confirmed the pins are correct in the 8451 user manual. Has anyone else found this? I have attached screen captures of my VI and Logic Analyzer. I tried the 8451 examples and the result is the same, the SCLK appears on the MOSI line. I don't think this would be a real big issue for what I want to do, but I find it strange. Am I missing something?

[Catherine-B]

Hi ashrek,

I know you double checked all of the connections, but just to triple check, which pins are you connecting to on the 8451 and the analyzer?

[ashrek]

Hi Catherine,

I am connecting to 14(mosi),15(MISO),16(SCLK).

Andrew

[Catherine-B]

Hi ashrek,

What about on the Logic Analyzer side? How are you connecting them to the Logic Analyzer? It looks like the Logic Analyzer supports SPI; are you using any SPI specific settings in the software? I am not familiar with the Logic Analyzer, but it seems like you can read any signal, or you can set it up to use SPI or another protocol. Is that the case?

[ashrek · Accepted solution]

Catherine,

I figured out the problme. After changing to a faster USB port and for the analyzer and increasing the sample rate I was able to get the SCLK to appear correctly. I can say this problem is resolved,

Thanks

Andrew