I have a large project with several C-series modules. Some have to be on the FPGA Interface so that is the interface I have had to choose. One of the modules is the NI-9870 4 port RS232 serial module, and it is only being used from the RTOS. Because it is going through the FPGA I can't use the standard VISA VIs. I've tried a few alternotives but nothing is satisfactory. The best I have come up with so far is to send serial data through DMA FIFOs between the RTOS and the FPGA, but even this is far too slow, with roundtrip times of ~300mS to exchange a handful of bytes. Does anyone know the most efficient way of using the ports on the NI-9870 from the RTOS when in FPGA Interface mode?
