National Instruments CAN 372139B-01 - Manual (Page 198)

Chapter 6 Automotive Diagnostic Command Set API for C
Automotive Diagnostic Command Set User Manual 6-34 ni.com
ndVWTPConnectionTest
Purpose
Maintains a connection channel to an ECU using the VW TP 2.0.
Format
long ndVWTPConnectionTest(
TD1 *diagRef);
Input
diagRef
Specifies the diagnostic session handle, obtained from ndOpenDiagnostic and passed
to subsequent diagnostic functions. Normally, it is not necessary to manually manipulate
the elements of this struct.
Output
Return Value
The return value indicates the function call status as a signed 32-bit integer. Zero means the
function executed successfully. A negative value specifies an error, which means the function
did not perform the expected behavior. A positive value specifies a warning, which means the
function performed as expected, but a condition arose that may require attention.
Use the ndStatusToString function to obtain a descriptive string for the return value.
Description
For the VW TP 2.0, you must periodically maintain the connection link to the ECU, so that
the ECU does not terminate it. You must execute this periodic refresh at least once per second.
This function sends a Connection Test message to the ECU and evaluates its response,
performing the necessary steps to maintain the connection.
There is no equivalent for the ISO TP (ISO 15765-2), as the ISO TP does not use a special
communication link.