External Clock Monitoring with NI-RFSA

Issue Details

I am building a software application based on the NI Vector Signal Transceiver (VST) device. Our system needs to monitor the presence of an external clock in the device if the end user chooses this type of clock option to drive the signal acquisition. Is there a specific API command in the NI-RFSA driver to check if the external clock is present? I use the Commit call, but it takes 10 seconds to return, and I need to be faster.

Solution

The PXI Vector Signal Transceiver (VST) combines a vector signal analyzer and vector signal generator with a powerful FPGA for real-time signal processing and control. The generation is commanded via the NI-RFSG driver, and the acquisition can be driven with the NI-RFSA or the NI-RFmx drivers.  

Each of these drivers include an API that supports different programming languages. This allows users to programmatically configure and command the VST. However, none of the drivers include an API call to monitor the presence or absence of an external clock. The closest option is the Commit call. While it is not designed for this purpose, the Commit command writes to the instrument's memory the settings and configuration the user chose. Therefore, it forces the device to ensure the selected clock can be used. That's the reason why this call can be used for this purpose.

Unfortunately, the Commit call takes 10 seconds to complete, and the user doesn't have an option to change that delay. Hence, the driver will take that time to verify whether the external clock is present or not.