Experimental Physics and
Industrial Control System

Olivier Zimmermann <[email protected]> · Wed, 21 Sep 2011 16:37:33 +0200

Hello,

I'm starting with EPICS and trying to have a PV read a SGL/Float32 value exposed by a modbus device (the value is stored on two 16bits-wide holding registers).

To achieve this I'm using "Driver Support for Modbus Protocol under EPICS".
http://cars9.uchicago.edu/software/epics/modbusDoc.html

Modbus data is retrieved as follows (i.e. using modbus function 4 to retrieve two 16bit words at address 9) :

drvAsynIPPortConfigure("INSTR","192.168.##.##:502",0,1,1)
modbusInterposeConfig("INSTR",0,5000)
drvModbusAsynConfigure("INSTR:ReadFloat32","INSTR",1,4,9,2,0,50, "InstrInterface")

What I just can't figure out is :

- How do I typecast this 32bit modbus data into a Float32 ?

- What "EPICS device support" should I use (asynFloat64, asynInt32...) ?

- Should my PV be an "ai" and where can I cast the right data type within ?

Thanks for any help,
oz

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System