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.
| Frame Type | ARBID | DLC | D0 | D1 | D2 | D3 | CRC | |
|---|---|---|---|---|---|---|---|---|
| ID | Remote Request | |||||||
| 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
Method3 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.
3.1 Setup Procedure
- Obtain an arbitrary waveform generator (Agilent AG33250 used in this example; any AWG from A33xxx series should work seamlessly), LabVIEW development Software Package (2016 or later), and a USB-to-GPIB interface that would allow LabVIEW to control the arbitrary waveform generator (AWG).
- Unzip and save ‘GenerateCANStream.vi’ to a local computer running the LabVIEW Development Software.
- Connect the AWG to the computer using the USB-to-GPIB interface. Connect the output of the AWG to the CANTX side of the CAN transceiver or directly to the CANRX of the CAN module reacting to the generated errors.
3.2 Input Windows
Figure 3-1 shows the various windows in GenerateCANStream.vi. Input windows are bordered in red.
- Error Generation:
- At this point, set the Forcing Error value to ‘None’. Configure this area later when generating CAN frames with errors.
- Configure the AWG (Waveform Generator
Properties):
- Set the appropriate GPIB instrument address.
- Set the I/O level and gain to the desired levels using the I/O Level and Gain. Verify the levels with an oscilloscope to ensure that they are correct prior to connecting to the CANRX pin of the CAN module or to the CANTX pin of the transceiver.
- Configure the bit-rate.
- Configure CAN Data Frame:
- Enter desired Arbitration ID (Message ID).
- Configure message length (in bytes – DLC).
- Enter desired data to be transmitted.
- Choose data frame or remote request.
- Press the Run button on the vi Front Panel to start generating CAN frames.
