Datasheet

CAN: Controller Area Network Lab using ST STM32 Cortex-M processors. www.keil.com

Viewing the CAN Frames with the Logic Analyzer (LA):

µVision has a Logic Analyzer (LA). This feature is also available using Serial Wire Viewer (SWV) on a real processor or the

simulator. You will also get the LA working with the Discovery board. ST-LINK V2 supports SWV. V1 does not. All Keil

ULINKs and J-Link (black case V 6 and later) support SWV. This is a very powerful ARM CoreSight debugging feature.

1. Close the Trace Data window and remove all breakpoints. (Type Ctrl-B). Click on RUN.

2. You can configure the LA while the program is running or while it is stopped.

3. Can_Demo.c has two global variables val_Tx and val_Rx. Find where these are declared near line 28.

4. Right click on val_Tx and select Add val_Tx to… and select Logic Analyzer. This will also open the LA up.

5. Repeat for val_Rx. Both variables will now be visible in the LA as shown below. Adjust the LA window size.

6. Adjust the range: Click on Setup… and highlight each variable in turn and set Display Range: MAX: to 0xFF.

7. Click on Close to return to the main µVision window. Select File/Save All. (optional)

8. If the program is not running, click on RUN to start it.

9. Click on Analog sweep 0…3.3V in the Toolbox as shown here:

10. Click on Zoom All and/or IN and Out to get an appropriate screen as shown below.

11. The values of the CAN Data byte 1 are displayed as they change.

12. You can select Signal Info, Show Cycles, Amplitude and Cursor.

13. Click on Stop in Update Screen if desired. You can also stop the program if you prefer.

14. Select Signal Info, Show Cycles, Amplitude and Cursor.

15. Move your cursor over the waveform to see the effects and the information about timings provided shown below:

TIP: If you have more than one CAN

controller in your processor you can

operate these as parallel receivers. Divide

the messages up with the Acceptance

Filters. This will help capture all the

messages on a very busy bus without

losing any. Each CAN controller will

handle its share of the messages. This

effectively multiplies the number of FIFO

buffer memories which is an excellent

method of capturing all the CAN frames.