National Instruments CAN 372139B-01 - Manual (Page 284)

Chapter 6 Automotive Diagnostic Command Set API for C
Automotive Diagnostic Command Set User Manual 6-120 ni.com
ndOBDRequestEmissionRelatedDTCs
Purpose
Executes the OBD Request Emission Related DTCs service. Reads all emission-related
Diagnostic Trouble Codes (DTCs).
Format
long ndOBDRequestEmissionRelatedDTCs(
TD1 *diagRef,
TD3 *DTCDescriptor,
TD4 DTCs[],
long *len,
LVBoolean *success);
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.
DTCDescriptor
A struct that describes the DTC records the ECU delivers:
typedef struct {
long DTCByteLength;
long StatusByteLength;
long AddDataByteLength;
unsigned short ByteOrder;
} TD3;
DTCByteLength indicates the number of bytes the ECU sends for each DTC. The
default is 2.
StatusByteLength indicates the number of bytes the ECU sends for each DTC’s
status. The default is 0 for OBD.
AddDataByteLength indicates the number of bytes the ECU sends for each DTC’s
additional data. Usually, there are no additional data, so the default is 0.
ByteOrder indicates the byte ordering for multibyte items:
0: MSB_FIRST (Motorola), default
1: LSB_FIRST (Intel)
This function interprets the response byte stream according to this description and
returns the resulting DTC records in the
DTCs struct array.