Configurable Error Generator for Controller Area Network

Trademarks

LabVIEW is a trademark of National Instruments Corporation.

C2000 and Code Compose Studio are trademarks of Texas Instruments Incorporated.

All trademarks are the property of their respective owners.

1 Introduction

The objective of this application report is to provide an easy-to-use hardware and software framework to generate and analyze different types errors in a CAN bus. Two different methods are presented:

GPIO method: A test-case that could be run on any applicable C2000 device. This provides visibility on a GPIO pin, if desired. A working C2000 target board and Code Compose Studio™ (CCS) IDE is all that is required.

LabVIEW method: This method is useful in case integration into a larger test setup (independent of a C2000 target) is desired. This needs the hardware outlined in Section 3.

For both methods, an oscilloscope with built-in CAN bus triggering/decoding is essential.

All simulated waveforms in this document were captured at the GPIO pin emulating the CAN transmit function. The effect of a CAN receiver node detecting an error and destroying the on-going frame will not be seen since the waveforms do not reflect true CAN bus activity, but only emulated CAN function. For this reason, the complete “CAN waveform” is seen in the oscilloscope captures. CAN frames shown in Table 1-1 were generated with GPIO and LabVIEW methods. These simulated frames were monitored with a CAN bus analyzer. The correct interpretation of the frames by the analyzer was validation that the frames are generated correctly and consistently.

Table 1-1 Generated CAN Frames

Frame Type		ARBID	DLC	D0	D1	D2	D3	CRC
ID	Remote Request	ARBID	DLC	D0	D1	D2	D3	CRC
Standard	No	0x45B	4	95	1A	23	45	0x5AD8
Standard	Yes	0x45B	4	n/a	n/a	n/a	n/a	0x238C
Standard	Yes	0x45B	0	n/a	n/a	n/a	n/a	0x7B43
Extended	No	0x1914A75B	4	95	1A	23	45	0x4101
Extended	Yes	0x1914A75B	4	n/a	n/a	n/a	n/a	0x4EB3
Extended	Yes	0x1914A75B	0	n/a	n/a	n/a	n/a	0x167C

2 Frame Generation – GPIO/CCS Method

This section explains how to configure error generation using the GPIO/CCS method. This should be used in conjunction with Figure 2-1.

Configure message length and bit-rate
- Configure message length in bytes (DLC)
- Configure bit-rate (in bps)

Hardware set up procedure:

CAN_GPIO_MODE

Select the GPIO that would generate the CAN bit stream.
Connect a jumper wire from the chosen GPIO to the selected CANRX pin.
Connection is direct between GPIO and CANRX pins. No transceiver involved.

CAN_DATALBCK_MODE

No external connections are needed.
CANTX data directly goes to the CANRX buffer using internal connection.

Configure CAN Data Frame
- Enter desired Arbitration ID (Message ID)
- Enter desired data to be transmitted
- Choose data frame or remote request

CCS-Use Watch Expression to monitor CAN-frame related variables

Generated 15-bit CAN CRC using polynomial 0xC599 can be monitored through the Expressions window in CCS.
The number of occurrences for stuffed bits can also be monitored in the Expressions window of CCS.

Figure 2-1 Frame Generation – GPIO/CCS Method

3 Frame Generation – LabVIEW Method

This section illustrates the various steps involved in generating CAN frames using the LabVIEW method, using ‘GenerateCANStream.vi’. It also explains the various indicators and configurable options in the Labview vi.