National Instruments CAN 372139B-01 - Manual (Page 25)

Chapter 4 Using the Automotive Diagnostic Command Set
© National Instruments Corporation 4-3 Automotive Diagnostic Command Set User Manual
General Programming Model
First, you must open a diagnostic communication link. This involves
initializing the CAN port and defining communication parameters such as
the baud rate and CAN identifiers on which the diagnostic communication
takes place. No actual communication to the ECU takes place at this stage.
For the VW TP 2.0, you then must establish a communication channel to
the ECU using the VWTP Connect routine. The communication channel
properties are negotiated between the host and ECU.
After these steps, the diagnostic communication is established, and you can
execute diagnostic services of your choice. Note that for the VW TP 2.0,
you must execute the VWTP ConnectionTest routine periodically (once per
second) to keep the communication channel open.
VW TP?
VW TP?
Done?
VW TP?
Yes
No
Yes
Yes
No
No
No
Yes
Open Diagnostic
VWTP Connect
Execute a
Diagnostic Service
Periodically Execute
VWTP ConnectionTest
VWTP Disconnect
Close Diagnostic