bi - serial rs485-modbus rtu communication (2 VFD's)

[ardahatunoglu]

Hey!

I need to send rpm and torque setpoint signals simultaneously to two different serial comm ports which are two seperately controlled variable frequency drives(VFD). The setpoints are for each second(1s - 10rpm - 10Nm, 2s - 20rpm - 20Nm, and so on ...) To two different serial ports . What kind of labview function/block you guys would suggest? 

[Ben]

See...

Data Communications >>> Modbus

You need only figure out the mapping and the data format and the docs on the widget you are controlling should tell you that.

Ben

[ardahatunoglu]

sooooo, I spend a little while trying to decipher your message but I couldn't get any useful info from it on sending(term might be syncronizing) 2 different signals at the same instant through 2 different serial ports. I know mapping and framing of modbus rtu and can communicate with my device without modbus library. Couldn't find any useful VI's in Modbus library that you referred which helps me to achieve what I had written above.

[Ben]

Put some numbers on "how simultaneous" it has to be.

Serial ports are often named as "ASRL" where the "A" stands for "asynchronous".

It could be as simple as writing both widgets at the same time and letting the OS take care of putting the data on the line.

Ben