ProFace RS485 Communication

[RammaR]

Hello. We've been using ProFace 4000 & 5000 series HMI's for a year or so now and have a new application we're stuck on. The issue is communicating with a device over a 2-wire RS485 serial connection.

When we try to send the sensor an inquiry string, we get nothing back. We know the sensor is functional because it responds to commands from a laptop via the OEM's software. But the sensor doesn't have any indicator lights or other way of telling if it is receiving the command.

Step 1 is to make sure we're sending the text string out of the ProFace HMI/PLC properly over the serial port. Ex: >001202V;F5 <cr>

Does anyone have any experience with configuring the serial port or writing the "script" to communicate over the RS485 port?

Never done this before and trying to learn. Thanks in advance.

 

[danw]

1) Try swapping the two data lines at one end. Sometimes manufacturers label them the opposite.

If the lines are swapped, the drivers are not damaged, but it won't work.

2) If the other end is 4 wire, connect (+) to (+), (-) to (-) to get 2 wire operation.

3) 2 wire RS-485 is by definition, half duplex (only one speaker, other end listens). If one device/end operates full duplex (starts speaking while the other end is still talking), it'll never work.

 

[RammaR]

Dan - thanks for the suggestion. Didn't seem to make any difference. I think it is connected properly, the issue is with our write command or the read back.

IO_WRITE_EX([p:EXT_SIO], databuf0, [w:[#MEMLINK]0500])

 

[Bullzi]

What does the command structure look like when you do it via your laptop? I have seen systems automatically add CR or LF to a command. The ProFace could be doing somthing like that to your command.

 

[RammaR]

It seems the ProFace databuffer isn't sending a <CR> with the command string. Now we're trying to figure out how to append a ASCII 13 or CR to the databuffer string.

 

[RammaR]

that was it, after adding a CR at the end of the string it's transmitting and receiving.

Thanks!

 

[RammaR]

We're successfully receiving data but what we're getting is correct one time and overlapping or partial the next time. The device is sending back a <cr> at the end of the response string and initiating the string with a specific character. Has anyone had experience with GP-Pro's extended script function and parsing or reading back a serial data stream?

Thanks