Hello All,
I'm hoping that someone out there can assit me with a problem I'm having with some serial communications. I'm using the NI 9068 which has three built in serial ports. Port 1 and Port 2 are RS-232 and Port 3 is RS-485. When I bought it I thought all three ports were RS-232 as I have three devices that I need to communicate with to the cRIO. I have in the past had good luck using a B & B electronics RS-232 to RS-485 converter on the same chassis.
I'm trying to communicate with a scale, and I have created VI's that work to communicate with the scale when I use one of the two RS-232 ports. However I cannot communicate with the scale when I try to use the RS-485 port and the B&B converter (model number 4WSD9R). I will either get a warning saying that the number of bytes at the port is equal to that which was read (i.e. 0 bytes) or an error -1073807298 when it actually does read something (for example /0/00/0) but not what it is supposed to be reading.
I have tested the hardware and the wiring to the converer by connected the RS-485 port to the converter then the converter to a RS-232 port. I will then write to the 485 port and read from the 232 port. The data transfers from one port to the other just fine. I have also switched the configuration to write at the RS 232 port and read from the RS 485 port, and again the data transfer just fine.
To me it seems as though there is some issue with the Bidirectinal communications. In case this is the problem I have the Rx crossing over to the Tx lines on the RS 485 side. I'm pretty sure this is correct of the communication described above would not work at all.
Thanks for any help that can be offered