# [Using Event Recorder](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/eventrecorder/) ## In this learning path - [Introduction](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/) - [Create and setup Keil MDK project](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/create/) - [Initialize the operating system](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/initialize/) - [Create RTOS threads](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/threads/) - [Build and run the application](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/build_and_run/) - [Using Event Recorder](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/eventrecorder/) - [Next Steps](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/_next-steps/) We saw in the last section that Keil MDK does not support semihosting. [CMSIS-View](https://arm-software.github.io/CMSIS_6/latest/View/index.html) provides [Event Recorder](https://arm-software.github.io/CMSIS-View/latest/evr.html) which can be used instead for the printf functionality. It’s supported for both FVPs and real hardware. ## Manage run-time environment Open the `Manage run-time environment` dialog, and enable `CMSIS-View` > `Event Recorder` (`DAP` variant). Enable `CMSIS-Compiler` > `STDOUT (API)`, and set to `Event recorder`. You’ll also need to enable `CMSIS-Compiler` > `Core`. 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: ```c #include "EventRecorder.h" ``` Add this function call to `main()`, before `osKernelInitialize()`: ```c EventRecorderInitialize(EventRecordAll, 1); // initialize and start Event Recorder ``` ## Set the Event Recorder timing source Navigate the project tree to locate `CMSIS-View` > `EventRecorderConf.h`, and open this file. Click the `Configuration Wizard` tab. Set `Event Recorder` > `Time Stamp Source` to `CMSIS-RTOS2 System Timer`, and save the file. This change will be reflected in the source code as: ```c #define EVENT_TIMESTAMP_SOURCE 2 ``` ## Define the Event Recorder buffer `EventRecorder.o` will use a buffer to store the generated data. This must be located in an uninitialized region of writable memory. Edit the scatter file, creating a new execution region (after `ARM_LIB_STACK`): ```c EVENT_BUFFER 0x20060000 UNINIT 0x10000 {EventRecorder.o (+ZI)} ``` If you get a link-time warning: ```c 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`: ```plaintext 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. Note that the RTX source contains many Event Recorder annotations. For ease of readability, click the `Filter` icon to hide these events. Ensure `STDIO` events are enabled. ![Event Viewer filter settings](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/ev_filter.png) *Event Viewer filter settings* Observe that printf output is in the form of the ASCII codes of the text output. ![Event Viewer showing ASCII output](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/ev_raw.png) *Event Viewer showing ASCII output* For this view it’s better to use [EventRecorder Data](https://www.keil.com/pack/doc/compiler/EventRecorder/html/group__EventRecorder__Data.html) rather than printf statements. ## EventRecorder Data Edit the `threads.c` file, and include the header file: ```c #include "EventRecorder.h" ``` Add a call in each thread to `EventRecord2()` with the thread number as the second parameter. For example, to output a `2` for `thread2`, use: ```c 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. Ensure `Unspecified Events` > `0x0` is enabled. The thread number is output as the first `Value`: ![Event Viewer showing thread data values](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/ev_data.png) *Event Viewer showing thread data values* ## Component Viewer To make these events more meaningful in the Event Recorder viewer, use the Component Viewer functionality. In a text editor, create a [Component Viewer Description File](https://www.keil.com/pack/doc/compiler/EventRecorder/html/SCVD_Format.html) (e.g. `rtos.scvd`) with the following: ```xml ``` 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. This file has now defined event `0x0`, and this is reflected in the filter view: ![Event Viewer filter with custom component](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/ev_component.png) *Event Viewer filter with custom component* These events are now processed into meaningful messages in the Event Recorder viewer: ![Event Viewer with Component Viewer decoded messages](https://learn.arm.com/learning-paths/embedded-and-microcontrollers/cmsis_rtx/ev_cv.png) *Event Viewer with Component Viewer decoded messages*