Indeed there is a LV ModBus library. You can find it here
I use a modbus protocol for our modules. I don't use the library, for me it is easier to compose the commands myself and read all the data from the modules.
It all depends on what you want to do and what you want to see
The Micro Motion RFT9739 transmitter can talk both HART and MODBUS protocols. If you are planning on using the labview interface for configuration of the transmitter, you should use MODBUS protocol.
Here is a link to the Micro Motion MODBUS Mapping Assignments manual. MODBUS Mapping Assignments Manual
I don't know when the ModBus library came available.
One of the reason for my solution was that I use this for testing the modbus modules. I want to see all data comming back from a module to be able to see all different kind of errors. Beside the standard commands we also use a lot of non standard modbus commands.
Sometimes I have to analyze modbus data to retrieve a error cause. It is handy to know the commands down to the byte level. Makes it easier to wire LV programs to help analyzing the data.
The Hart protocol is modulated on top of the 4-20mA current loop. You always have to use a special Hart terminal/programmer for communication.
Sorry for delay in reply but got waylaid with other problems on project and only just managed to get back to this issue.
Initially to check things out I have been using a Hart modem from Microflex and the free version of the European Consortium Hart software 'PACTware 3.0. This allowed me to talk to the Micro motion RTF 9739 and get basic information such as ID, flow rate etc, so the hardware coms was confirmed. Unfortunatly Emerson do not support DTM files so that was as far as I could go.
I then tried your Hart vi's but keep getting communications error. I know the hardware is ok but cannot see where the problem could be.
As suggested l also tried using Modbus from the NI librarys talking over the RS485 half-Duplex link (used ni PCI RS486 8 channel card) but no luck there either. Oscilloscope sees the RS485 data stream so I know it is present at the flowmeters RS485 connection but no response from the unit.
Totally stumped and out of ideas!
With the MMI RFT9739 transmitter, trying to communicate MODBUS over RS485. Please confirm dipswitch number 5 is in the OFF position (STD COMM). Standard communication on the 9739 is 9600 baud, 1 stop bit, ODD parity. The default address is address 1.
If the RFT9739 has a local display, you can configure the communications through the display. All of this information is available in the RFT9739 user manual on page 10.
For HART communications, as you stated, you could get a response from other software. The 9739 will respond to any HART universal command. I haven't checked the linked software.
If you are having trouble with the 9739 communications, give the 1-800 number a call. Ask for me. I can probably talk you through any questions you have in about 10 minutes.
Thanks for info. Already tried the settings you suggested, but no luck. Tried the std comms on 5 and also tried the user defined, but with same spec as std (just in case??, live in hope!), but still no joy. Unsure if the 1-800 number will get me through from France?
The User Definded setting defaults to (oddly enough) HART protocol at 1200 baud, one stop bit, ODD parity. Default address is 0. Yes, this is on the RS485 circuit, not the mA connection.
However, if you are not connecting with MODBUS, I doubt the user defined setting will work either.
Two choices. First, any chance of getting a bus trace to see the actual commands being sent to the transmitter (and maybe the response).
Second, I don't want to use if the transmitter is working properly with mA or frequency output. A master reset can be done on the transmitter. This will wipe out all configuration information. All calibration information will have to be re-entered. Dip switch 4,5,6, and 10 in the ON position, followed by a power cycle. Then reset all dip switches to the OFF position, then power cycle again. Then try connecting to the STD COM setting of MODBUS rtu, 9600 baud, 1 stop, ODD parity, MODBUS address 1 on connections 26 and 27. (By the way RFT9739 RS485 polarity is reveresed from normal, B is positive, and A is negative)
Also, we do have customer support in the Netherlands, they have a good English speaking trouble shooter named Albert, if he is available. Look at the back of any manual for the correct phone number.