Error 65: Serial port timeout

[Beginer LabVIEW programmer]

Hello,

I have communicated with Modbus protocol to three watlow96 using RS-232/485 converter. However, when I increase the number of watlows to 4 or more it gives me the following error: Serial port timeout; bytes not received at serial port. Increasing the timeout didn't help!

Can any one help me?

Thanks,

Nur

[DiegoF]

Hi,

A timeout error is that the serial port is not receiving the data within a specified amount of time. I assume that you are using the RS-232 port of your PC.

Since the port initially works I don't think it is anything on the PC. You should focus on the external connections. are the devices still sending data?.

ou can also use hyperterminal to test whether LabVIEW has anything to do.

Hope this helps
DiegoF
National Instruments.

[Beginer LabVIEW programmer]

Hi DiegoF,

Thanks for your help. When I connect to four or more watlows non of the devices send data and there is no communication with any devices at all. However, as soon as I decrease the # of watlows to 3 it starts communication. This is in LabVIEW MODBUS communication mode and the same is also true with WatVIW setup software. The WatVIEW Setup software detects only 4 watlows though there are 10 watlows connected. The port on my PC is RS-232 and the converter is K2-ADE RS232-RS485. Do you think using PCI 2 port velocity RS422/485 CC-313 will help?

Thanks,

Nur

[Ben]

Another thought;

RS-485 dicatates termination resistors at both ends of the transmision line. Sometimes thes are built into the interface, sometimes you have to add them.

Make sure the hardware level is correct.

Ben