This section describes how the Event Recorder collects event data, generates time stamps, and transfers this information via a debug unit to a host computer.

The Event Recorder is implemented in the target application using the software component CMSIS-View:Event Recorder which adds the source file EventRecorder.c to the application. Each event is stored in a 16-byte structure that is composed of a 16-bit id, 32-bit time stamp, two 32-bit data values and consistency check values.

To store these events, a circular buffer is provided that can store a minimum of 8 events. The size of this circular buffer is configurable with the #define EVENT_RECORD_COUNT.

Event id

The Event Data Recording functions get a parameter id that is composed of level, component number, and message number as shown below:

id	bits	Description
message number	0..7	identifies the event message information of the software component
component number	8..15	identifies the software component (also used for filtering, see table below)
level	16..17	specifies the class of the message for filtering (see table below)
— (reserved)	18..31	set to 0

The level specifies the category of the event message and can be used for filtering:

level	Message relates to ...
EventLevelError = 0	Run-time error
EventLevelAPI = 1	API function call
EventLevelOp = 2	Internal operation
EventLevelDetail = 3	Additional detailed information of operations

The component number specifies the software component that the event message belongs to and can be also used for filtering:

component number	Relation to software components
0x0 .. 0x3F (0 .. 63)	software components of the user application
0x40 .. 0x7F (64 .. 127)	third party middleware components
0x80 .. 0xED (128 .. 237)	MDK-Middleware components
0xEE (238)	Fault component
0xEF (239)	Start/Stop events for Event Statistic information
0xF0 .. 0xFC (240 .. 253)	RTOS kernel
0xFD (253)	Inter-process communication layer (multiprocessor systems)
0xFE (254)	printf-style debug outputs
0xFF (255)	Event Recorder messages

The following sections describe:

Configuration : explains the set-up of the Event Recorder and the configuration of a user provided timer.
Event filtering : shows how to limit the amount of data that is displayed in the Event Recorder window.
Resource requirements : lists the technical data and explains the hardware and software requirements.

Configuration

Adding the software component CMSIS-View:Event Recorder to a project will copy the file EventRecorderConf.h into the project that is used to define the configuration parameters of the Event Recorder. It uses Configuration Wizard Annotations, so IDEs that support this can also show a graphical representation of the file:

EventRecorderConf.h in Configuration Wizard View

Following configuration parameters are defined in the EventRecorderConf.h file:

Option	#define	Description
Number of Records	`EVENT_RECORD_COUNT`	Specifies the number or records stored in the Event Record Buffer. Each record is 16 bytes.
Time Stamp Source	`EVENT_TIMESTAMP_SOURCE`	Specifies the timer that is used as time base. Refer to Time stamp source below for more information.
Time Stamp Clock Frequency [Hz]	`EVENT_TIMESTAMP_FREQ`	Specifies the initial timer clock frequency.

‍Note

Set the time stamp clock frequency to your target's core clock frequency to avoid problems in determining the correct frequency.

Time stamp source

The following time stamp sources can be selected:

Source	Description
DWT Cycle Counter	Default setting. The DWT cycle counter is part of the CoreSight debug interface. DWT is not available with Cortex-M0/M0+/M23. uVision can simulate DWT using a script.
SysTick	System tick timer is available on most Cortex-M processors. But in power-down modes it might be disabled.
CMSIS-RTOS2 System Timer	The system tick counter provided by a CMSIS-RTOS2 compliant real-time operating system.
User Timer (Normal Reset)	User-defined timer that stops by any system reset. Refer to Event Recorder - Timer for more information.
User Timer (Power-On Reset)	User-defined timer that stops only by power-on reset. Refer to Event Recorder - Timer for more information.

‍Note

When DWT Cycle Counter is selected on Cortex-M0/M0+/M23, a warning is issued at compile time:
Invalid Time Stamp Source selected in EventRecorderConf.h!

When using the CMSIS-RTOS2 System Timer, it is strongly recommended to set up the Time Stamp Clock Frequency [Hz] (see above) to the correct value to avoid display problems in the Event Recorder and System Analyzer windows.

Configure for targets without DWT Cycle Counter

Arm Cortex-M0/M0+/M23 processors do not offer the DWT Cycle Counter and require therefore alternative time-stamp sources.

SysTick

For applications that do not use the SysTick timer, you may configure EventRecorderConf.h with:

#define EVENT_TIMESTAMP_SOURCE 1 // use SysTick

#define EVENT_TIMESTAMP_FREQ 25000000U // processor core clock (input frequency to SysTick)

CMSIS-RTOS2 System Timer

For applications that use a CMSIS-RTOS2 compliant RTOS (SysTick timer used by RTOS), you may configure EventRecorderConf.h with:

#define EVENT_TIMESTAMP_SOURCE 2 // use CMSIS-RTOS2 System Timer

#define EVENT_TIMESTAMP_FREQ 25000000U // processor core clock (input frequency to SysTick)

DWT Cycle Counter with µVision simulator

The DWT Cycle Counter can be simulated with the following debug initialization file, for example Debug_Sim.ini:

MAP 0xE0001000, 0xE0001007 READ WRITE
 
signal void DWT_CYCCNT (void) {
  while (1) {
    rwatch(0xE0001004);
    _WWORD(0xE0001004, states);
  }
}
 
DWT_CYCCNT()

Resource requirements

Technical data of Event Recorder firmware

Target: Cortex-M3 using DWT cycle counter as timer

Parameter	ARMCC V6.13.1	ARMCC V6.13.1
Compiler options	-Os	-O3
ROM size	< 1.7k bytes	< 3.4k bytes
RAM size @8 records (min)	292 bytes	292 bytes
RAM size @64 records (default)	1188 bytes	1188 bytes
EventRecord2 (id+8bytes)	197 cycles	184 cycles
EventRecord4 (id+16bytes)	343 cycles	319 cycles
EventRecordData (id+8bytes)	276 cycles	252 cycles
EventRecordData (id+16bytes)	425 cycles	397 cycles
EventRecordData (id+24bytes)	554 cycles	519 cycles
EventRecordData (id+32bytes)	685 cycles	643 cycles

‍Note

ROM size is specified for image with all Event Recorder functions being used.

RAM size can be calculated as 164 + 16 * <Number of Records> (defined by EVENT_RECORD_COUNT in EventRecorderConf.h).

Timing was measured in simulator (zero cycle memory, no interrupts). Function parameter in application is not considered.

Usage of records by Event Recorder functions

Function	Number of Records used
EventRecord2	1
EventRecord4	2
EventRecordData	(event data length + 7) / 8