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LabVIEW drivers - FLOW-BUS chained command utility
The Bronkhorst FLOW-BUS protocol doesn't only provide commands to read the many device parameters of over 25 different devices, it also allows to combine commands into a single command using the technique of chaining. So instead of having several commands for reading a set of parameters from a particular device these commands can be combined. The reason to do this is to shorten the size of the message(s) that must be written to that device as well as the size of the message that must be written by that device in reply to the command. And in serial communication a shorten message means less time.
The way that commands are chained depends on the parameters being organized into groups called processes. The FLOW-BUS protocol uses the first bit (MSB) of the process number and the parameter number (e.g. parameter number within that process) to indicate that either the process or the parameter is chained. If there are commands for different processes they can be chained at process level. If there are commands for different parameters within the same process they can be chained at parameter level.
The rules for chaining command are described in the instruction manual 'RS232 interface with FLOW-BUS protocol for digital multibus Mass Flow / Pressure instruments' (Doc. no. 9.17.027Q).
The presented utility (flowbus cc.vi) offers an easy way to create (chained) parameter request commands using the FLOW-BUS RS232 ASCII protocol. The requirements to create commands can be entered in an easy left-to-right manner:
With this requirements set a command can be created. For each parameter, as defined for FlowDDE, the actual process and parameter number as well as the required chaining bit(s) and data type will be selected.
If the device is connected to the selected serial port it can also be tested.
If there is any error while communicating with the device, the utility will show the corresponding error message. If there is a response from the device it will be shown and in the case of easy commands, or rather commands that request only a single parameter, the value of the response will be shown separately.
This file includes:
Bart Boshuizen, 2012/09/27