Set up Code Coverage

Prerequisites

You must have Keil MDK installed.

Code coverage can be performed on any project that runs on a suitable target. You shall use one of the standard RTX examples that runs on the supplied Cortex-M FVP.

Import and build the example project

Open the uVision IDE, and then the Pack Installer.

In the Devices tree, select ARM > ARM Cortex M3 > ARMCM3 (use search text box if necessary).

With this Device selected, click on the Examples tab, and Copy the CMSIS-RTOS2 Blinky (uVision Simulator) example.

Open the project in MDK, and build.

Set up debug with FVP

By default, this project uses the legacy simulator provided with MDK, which does not support code coverage.

To run on the FVP, open ‘Options for Target…’, navigate to Debug pane, and select Models Cortex-M Debugger from the Use: pull-down. Click Settings, and under Command, browse for one of the supplied FVPS in the ARM\FVP\ folder of your MDK installation (eg FVP_MPS2_Cortex-M3_MDK,exe).

Specify a Coverage File, and enable Load and Store of that file. Because of the way that the data is created, code coverage cannot be updated in real-time.

Click OK to save settings, then start a debug session (Ctrl+F5).

If not already open, navigate to View > Analysis Windows > Code Coverage to enable that view.

Run the application for a few seconds, going through a number of iterations of the LEDs turning on and off. Observe that the Code Coverage data is not updated (with FVP). Close the debug session, and start a new one to load the coverage data. Code coverage data is now displayed in the Code Coverage window.

Investigate the code coverage output

Observe the report, detailing the percentage of instructions that have been executed for each function. Browse for an ‘interesting’ record, for example osRtxThreadDelayTick, within rtx_thread.c. You should see less than 100% of the instructions executed, including one or more instructions not fully executed.

Click on that function (in the Code Coverage window) to put the source and disassembly views in focus on that function.

Code that has been fully executed is highlighted in green.

Code that has not been executed (such as some of the switch-cases) are not highlighted.

Code that has not been fully executed is highlighted in orange or blue. What this means is, for example, a conditional branch instruction where only one of the true and false conditions have been met, and so the other branch path of that instruction has not been tested by that run. Orange means that the branch is never taken, blue that it has always been taken.

It is also possible to output the code coverage information on the MDK command line. To show all, simply use:

    

        
        
            coverage
        
    

You can also filter the report by source file or function. In the Code Coverage view by the Module pulldown, else on the command line with, for example:

    

        
        
            coverage \blinky.c
coverage \blinky.c\main