Actually what you have shown is not an error but a warning. It has a postive error number and the status is an OK check mark. It is a warning saying you received exactly as many bytes as you asked for, and more may be available. It is occurring in the MB serial Init VI.
Now that MB Serial Init VI does something that's good, then a couple things that are pointless. I think this was a poorly written VI. First it sets all the settings for the serial port, baud rate, parity, timeout, termination character. That is all good. Then it proceeds to determine how many ports are in the receive buffer than proceeds to read them and do nothing with them. This effectively flushes the receive buffer. That is where the warning is being generated. It reads exactly as many bytes as are in the buffer. It should probably just tell it to clear this specific warning/error because it is meaningless, but instead it just passes it on. Then the VI proceeds to forcefully flush transmit and receive buffers. While this is okay in theory, why did it bother reading the data in the receive buffer. It does nothing with it, and proceeds to flush it anyway.
I recommend that you don't use the MB Serial Init VI at all. Just use the Serial Config VI that is part of the normal VISA Serial palette. Looking back at some of my Modbus code, I don't think I ever used that Serial Init VI. I can't remember if I tried and came across the same issue or not. I either used the Serial Config VI, or just went with the serial port settings that I hard coded in either MAX or windows.
Get rid of the MB Serial Init VI, use the Serial Config VI and try again.
I don't know if this will actually solve your 6101 error. From what I can see, it shouldn't be causing it. It looks like the 6101 error code is originated from the subVI MB Serial String to MB Data Unit within MB R (which is a part of MB WR) . The 6 seems to be a digit that LabVIEW itself added on to a 101 error from the Modbus Exception Code. I looked on Modbus.org http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf and couldn't find a 101 error. There is a 1 error which means Illegal Function. Looking at your screenshot in, I don't even know how you got the description Timeout Error, because the MB Serial String to MB Data Unit would return the exception code as MODBUS Exeption Code: 6101.
As for your hardware setup, there are a lot of connections going on going USB to RS-232 to RS-485 back to RS-232. I would recommend getting a USB to 485 converter to eliminate one extra device.
Also, why are you still trying to read 20 addresses? I thought you originally said you only wanted to read 2 addresses. And double check your starting address because originally you wanted 43293 and now you are starting at 43007 (give or take 1).
Message Edited by Ravens Fan on 02-13-2009 12:23 AM
