BRONKHORST®
5 DDE COMMUNICATION BY CLIENTS
5.1 BASIC PARAMETER COMMUNICATION
Client applications communicate to the FlowDDE server by using DDE messages. Before messages can be exchanged, a
DDE link had to be made. A DDE link consists of three parts: the server, the topic and an item. For separation the
characters '|' and '!' may be used, so a DDE link in e.g. Microsoft Excel becomes Server|Topic!Item.
For standard instrument parameters and the FlowDDE server, these are:
• Server: FlowDDE or FlowDDE2
• Topic: C(X) for channel X
• Item: P(Y) for parameter Y
An example of a DDE link in a Microsoft Excel cell is =FlowDDE|’C(1)’!’P(8)’ to read parameter 8 of channel 1.
5.2 SPECIAL OPTIONS
5.2.1 Channel 0
Special commands can be sent to FlowDDE by means of the command channel 0, C(0). This channel is not related to
any FLOW-BUS instrument, but is for FlowDDE control only. Channel 0 contains P(0) , P(1) and P(2) items only.
P(0) is the command parameter. Write a number to P(0) will trigger FlowDDE to read all parameter values from one or
more channels and update the parameter values at the DDE level. To read a smaller amount of parameters, parameter
groups can be read. Which parameters are in which group can be found in the parameter list.
• C(0)!P(0) = X read values of all parameters of channel X
• C(0)!P(0) = X.Y read values of all parameters in group Y of channel X
• C(0)!P(0) = -1 read values of all parameters of all channels
Other special actions can be triggered by P(0):
• C(0)!P(0) = -2 open a log file, read all parameter values on all channels, and close the file.
• C(0)!P(0) = -3 bring the main window to the front
• C(0)!P(0) = -4 bring the FLOW-BUS configuration window to the front
• C(0)!P(0) = -6 bring the Poll time window to the front
• C(0)!P(0) = -7 bring the System settings window to the front
• C(0)!P(0) = -8 restart the communication
• C(0)!P(0) = -9 terminate FlowDDE
• C(0)!P(0) = -10 minimize FlowDDE
P(1) is the read status information channel. When FlowDDE is reading data from the FLOW-BUS, all status/error
messages will be send to this parameter. When the value of this parameter is 0, everything is OK, otherwise will
contain the status/error message.
P(2) is the write status information channel. When a client application sends data to FlowDDE and FlowDDE sends the
values to the FLOW-BUS, any status/error messages will be send to this parameter. When the value of this parameter
is 0, everything is OK, otherwise will contain the status/error message.
5.2.2 Parameter 0
Similar to the way parameter 0 of channel 0 can be used to read parameters from any channel, parameter 0 of any
channel can be used to read parameters from that channel:
• C(X)!P(0) = Y read value of parameter Y of channel X
• C(X)!P(0) = Y-Z read values of parameters Y to Z of channel X
• C(X)!P(0) = GROUPY read values of all parameters in group Y of channel X
• C(X)!P(0) = ALL read values of all parameters of channel X
Page 16 FlowDDE 9.17.067
(14 paginas)
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