05-29-2024 06:35 AM
Lately I tried using the NI-9871 C-Module after a long time of abstaining, and the communication didn't work. Maybe I made a mistake in signal cable connection. But there is another posiibility: lack of supply power. I remember few years ago a case that the power cable (the module needs a separate power cable) had poor contact and the module had no power - I replaced the cable then and the problem was fixed.
It would be nice to have a quick way to distinguish lack of power supply from lack of signals. Is there some signal that can be read to know whether the NI-9871 is powered or not?
Thanks in advance, Jerzy
06-01-2024 02:50 PM
An idea which I tried to test right now, but it's too late today to finish the test: connect RTS(+/-) with CTS(+/-), change RTS and examine CTS if it changes accordingly. This assumes these RTS/CTS signals are really used on RS-485...
06-15-2024 01:51 PM
I tested the method, using a cable with a female connector (NI's serial cable has a male connector), on which I connected RTS+ with CTS+, and RTS- with CTS-. Seems the result was: when NI-9871 was powered, CTS on the port followed RTS when the RST changed; when the power was lost, CTS kept its last value. The program was for RT part of cRIO-9039 in Scan Mode. I hope for FPGA program result will be the same.