Implementing Checksum Algorithm E2E Profile 1A with NI VCOM RBS Descriptor Tool

NI-VCOM defines many common checksum algorithms in RBS Descriptor tool. The users can implement checksum easily compared to custom interface way introduced in Using NI-VCOM Toolkit to Define the Custom Checksum for CAN Application. E2E profile 1A is widely used. This article will introduce how to implement it with RBS Descriptor tool.

1. Add the VCOM custom device in VeriStand. Click Create VCOM Descriptor to open the RBSConfig tool.
2. Right-click in the Datapool, then select New Network>>CAN or FlexRay Network>>Create single network to add the database file.
3. Find the checksum signal in the Datapool, then right-click on it and select Copy2Config. 

4. Find the checksum signal in the Configuration, then left click it and choose Change to AutoSignal.

5. In the drop-down menu of Auto Signal type, select ChecksumUserJ1850. 

• CRCMask: Determine the data bytes that are used for the CRC calculation. For example, CRCMask 254(1111 1110 in binary) means that byte 1 to byte 7 of data bytes will be used for checksum calculation.
• Initial Value: CRC initial value. Default value is 255. For E2E Profile 1A, it should be 0.
• FinalXORValue: XOR value at the end of the CRC algorithm. Default value is 255. For E2E Profile 1A, it should be 0.
• UserByteBefore: These bytes are used before the data bytes for the checksum calculation. Data ID can be filled here. The first byte is the low byte of Data ID and the second byte is the high byte of Data ID.
• UserByteAfter: These bytes are used after the data bytes for the checksum calculation. Leave it empty for E2E Profile 1A.

       Fill the above parameters as follows, then click Execute.

6. Click the checksum signal in Auto Signals. In the Details, Delete the element in ChecksumUserBytesAfter by clicking the three points on the right side, then clicking Remove.

7. Click the three points on the right side of ChecksumUserBytesBefore to edit the Data ID. 

            For example, the Data ID of this frame is 19870 (0x4D9E in hexadecimal). You should fill the ChecksumUserBytesBefore as the follows.

8. Right-click on the database file in Configuration, then select Save as XML to save the configuration.