Using Event Recorder

We saw in the last section that Keil MDK does not support semihosting.

Event Recorder can be used instead for the printf functionality. It is supported for both FVPs and real hardware.

Event recorder functionality can be further extended by the Keil MDK Component Viewer . Annotations can be made in the application code or software component libraries. These annotations are stored in an event buffer.

Manage run-time environment

Open the Manage run-time environment dialog, and enable Compiler > Event Recorder (DAP variant).

Enable Compiler > I/O > STDOUT, and set to EVR (Event recorder) mode.

Click OK to save.

Add Event Recorder to main

Add a function call to initialize the event recorder. Open main.c in the editor.

Include the header file:

    

        
        
            #include "EventRecorder.h"
        
    

Add this function call to main(), before osKernelInitialize():

    

        
        
            	EventRecorderInitialize (EventRecordAll, 1);	// initialize and start Event Recorder
        
    

Set the event buffer

The event buffer must be located in an uninitialized region of writable memory.

Edit the scatter file, creating a new execution region (after ARM_LIB_STACK):

    

        
        
            	EVENT_BUFFER 0x20060000 UNINIT 0x10000 {EventRecorder.o (+ZI)}
        
    

If you get a link-time warning:

    

        
        
            Warning: L6314W: No section matches pattern EventRecorder.o(ZI).
        
    

Verify that Link-time optimization was disabled in C/C++ (AC6) tab in the Target Options dialog.

Build and run the example

Save all files, and build (F7) the example.

Click Debug (Ctrl+F5), then Run (F5) to start the application.

The thread output is now displayed in the printf viewer:

    

        
        
            hello from thread 1
hello from thread 2
hello from thread 3
hello from thread 1
hello from thread 2
...
        
    

Event recorder view

Use the menu (View > Analysis Windows > Event Recorder) to open the viewer.

Observe that printf output is in the form of the ASCII codes of the text output.

For this view it is better to use EventRecorder Data rather than printf statements.

EventRecorder Data

Edit the threads.c file, and include the header file:

    

        
        
            #include "EventRecorder.h"
        
    

Add call in each thread to EventRecord2() with the thread number as the second parameter, for example:

    

        
        
            void __attribute__((noreturn)) thread2(void *argument){
	for(;;){
		printf("hello from thread2\n");
		osDelay(1000);
		EventRecord2 (1+EventLevelAPI, 2, 0);
	}
}
        
    

Save all files, and rebuild (F7) the example.

Click Debug (Ctrl+F5), then Run (F5) to start the application.

Observe the events in the Event Recorder viewer. Use the filter to hide STDIO events, which shall remove the printf strings.

The thread number is output as the first Value:

Component Viewer

To make these events more meaningful in the Event Recorder viewer, use the Component Viewer functionality.

Create a Component Viewer Description File (e.g. rtos.scvd) with the following:

    

        
        
            <?xml version="1.0" encoding="utf-8"?>
 
<component_viewer schemaVersion="0.1" xmlns:xs="http://www.w3.org/2001/XMLSchema-instance" xs:noNamespaceSchemaLocation="Component_Viewer.xsd">
  <component name="MyExample" version="1.0.0"/>    <!-- name and version of the component  -->
 
    <events>
      <group name="My Events Group">
         <component name="EVR_Demo" brief="RTOS_Example" no="0x00" prefix="EvrNetMM_" info="Demo"/>
      </group>  
 
      <event id="1" level="API" property="Logging" value="goodbye from thread %d[val1]" info="Example output"  />
	  </events>
 
</component_viewer>
        
    

Exit the debugger, and return to Target Options > Debug, and click Manage Component Viewer Description Files.

Click Add Component Viewer Description File, and browse for the above. Save the settings.

Click Debug (Ctrl+F5), then Run (F5) to start the application.

Observe these events in the Event Recorder viewer, optionally filtering out STDIO.

Observe RTX events in the Event Viewer

The RTX source contains many Event Recorder annotations. To see these events in the viewer, return to the IDE, and open the Manage run-time environment dialog.

Enable CMSIS > RTOS2 (API) > Keil RTX5, but now select Source variant. Click OK to save. Rebuild the application.

Click Debug (Ctrl+F5), then Run (F5) to start the application.

Observe the events in the viewer, filtering as appropriate.

If no RTOS events are visible, verify that they are enabled in Target Options > Debug > Manage Component Viewer Description Files.