# vTaskStartTrace buffer size

**URL:** <https://forums.freertos.org/t/vtaskstarttrace-buffer-size/5515>\
**Category:** Kernel\
**Created:** [January 18, 2008, 4:31pm UTC](https://forums.freertos.org/t/vtaskstarttrace-buffer-size/5515 "2008-01-18T16:31:33Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\
**Post date:** [January 18, 2008, 4:31pm UTC](https://forums.freertos.org/t/vtaskstarttrace-buffer-size/5515/1 "2008-01-18T16:31:33Z")

</div>

**[natanel](https://sourceforge.net/u/natanel/)** wrote on [Friday, January 18, 2008](https://sourceforge.net/p/freertos/discussion/382005/thread/f5cb7b18/#0b75):

Hi  
first sorryfor posting it in another thread, this question should be new thread

I am using vTaskStartTrace to trace tasks switch.  
and sending the data through the usb port which then is read and plot in matlab.

code:  
#if ( configUSE\_TRACE\_FACILITY == 1 ) //debug  
if((sxUSBMessage.sValue1 & TASKS\_TRACE\_DEBUG)==TASKS\_TRACE\_DEBUG)&nbsp;&nbsp;&nbsp;  
{  
void \* pvBuffer;  
unsigned portLONG ulBufLength;

// write task list  
vTaskList( (&nbsp; (signed portCHAR \*)(&(scDebugBuff[0])) ) );&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

// length of written data  
ulBufLength=ulGetBufferLength(); //just return trace buf length in byte with out stoping trace  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  
// place of putting length of data  
pvBuffer=((void \*)(&(scDebugBuff[DEBUG\_BUF\_LENGTH-sizeof( unsigned portLONG )])));  
// putting length of data  
\*( unsigned portLONG \* ) pvBuffer = ( unsigned portLONG ) ulBufLength;  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  
// start new trace  
ulTaskEndTrace();  
pvBuffer=((void \*)(&(scDebugBuff[DELTA\_TASK\_LIST])));  
vTaskStartTrace( ((signed portCHAR \*)(pvBuffer)),DEBUG\_BUF\_LENGTH-DELTA\_TASK\_LIST-sizeof( unsigned portLONG ));  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  
// send trough USB  
Usb\_write\_endpoint\_in( (unsigned char \*)scDebugBuff, DEBUG\_BUF\_LENGTH, DEBUG\_BUF\_LENGTH, ONE\_SEC\_TIMERATE\>\>2);  
}&nbsp;&nbsp;&nbsp;  
break;  
#endif&nbsp;&nbsp;&nbsp;

from matlab size it look like that  
dummy request for debug  
pause 200 msec  
request for debug  
pause 200 msec  
request for debug  
pause 200 msec  
request for debug  
pause 200 msec  
request for debug  
pause 200 msec  
request for debug

getting 1 around sec of tasks switch trace

then looking on the data at matlab it is two 32 bit size numbers one tick time/number and second tasks num  
which is a waste of space (for up to 6 tasks switch in one msec and tracing for up to 500 msec it is 8\*6\*500=24000 byte in mcu RAM)  
task num can be 8 bit size (up to 255 tasks)  
(and time can be one 32 bit start time and then 16 bit delta times)

I tried to modify it by changing the define

/\*  
\* Macro that writes a trace of scheduler activity to a buffer.&nbsp; This trace  
\* shows which task is running when and is very useful as a debugging tool.  
\* As this macro is called each context switch it is a good idea to undefine  
\* it if not using the facility.  
\*/  
#if ( configUSE\_TRACE\_FACILITY == 1 )  
#define vWriteTraceToBuffer()&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
{&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
if( xTracing )&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
{&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
static unsigned portBASE\_TYPE uxPreviousTask = 255;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
if( uxPreviousTask != pxCurrentTCB-\>uxTCBNumber )&nbsp;&nbsp;&nbsp;   
{&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
if( ( pcTraceBuffer + tskSIZE\_OF\_EACH\_TRACE\_LINE ) \< pcTraceBufferEnd )&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
{&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
uxPreviousTask = pxCurrentTCB-\>uxTCBNumber;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
\*( unsigned portLONG \* ) pcTraceBuffer = ( unsigned portLONG ) xTickCount;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
pcTraceBuffer += sizeof( unsigned portCHAR ); /\* was portLONG \*/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
\*( unsigned portCHAR \* ) pcTraceBuffer = ( unsigned portCHAR )uxPreviousTask;&nbsp;&nbsp;&nbsp; /\* was portLONG \*/&nbsp;   
pcTraceBuffer += sizeof( unsigned portLONG );&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
else&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
{&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
xTracing = pdFALSE;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
&nbsp;&nbsp;&nbsp; }

#else

&nbsp;&nbsp;&nbsp; #define vWriteTraceToBuffer()

#endif

in task.c

but this just freeze my MCU (evk110 board-atmel 32bit U3A)

any ideas were and how to do it right

regards  
Natanel

---

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**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\
**Post date:** [January 18, 2008, 4:32pm UTC](https://forums.freertos.org/t/vtaskstarttrace-buffer-size/5515/2 "2008-01-18T16:32:55Z")

</div>

**[natanel](https://sourceforge.net/u/natanel/)** wrote on [Friday, January 18, 2008](https://sourceforge.net/p/freertos/discussion/382005/thread/f5cb7b18/#0b75/a2aa):

some how I keep see my question post as comment to another thread - sorry for the mess

---

<div class="post-metadata">

**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\
**Post date:** [January 18, 2008, 8:12pm UTC](https://forums.freertos.org/t/vtaskstarttrace-buffer-size/5515/3 "2008-01-18T20:12:33Z")

</div>

**[natanel](https://sourceforge.net/u/natanel/)** wrote on [Friday, January 18, 2008](https://sourceforge.net/p/freertos/discussion/382005/thread/f5cb7b18/#0b75/c94d):

copy past mistake  
pcTraceBuffer += sizeof( unsigned portLONG );   
is  
pcTraceBuffer += sizeof( unsigned portCHAR ); \

---

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**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\
**Post date:** [January 18, 2008, 8:37pm UTC](https://forums.freertos.org/t/vtaskstarttrace-buffer-size/5515/4 "2008-01-18T20:37:22Z")

</div>

**[sotd](https://sourceforge.net/u/sotd/)** wrote on [Friday, January 18, 2008](https://sourceforge.net/p/freertos/discussion/382005/thread/f5cb7b18/#0b75/c94d/c524):

Do you mean this fixes your problem or simple that this was just a mistake in your post and you still have a problem?

---

<div class="post-metadata">

**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\
**Post date:** [January 18, 2008, 9:03pm UTC](https://forums.freertos.org/t/vtaskstarttrace-buffer-size/5515/5 "2008-01-18T21:03:21Z")

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**[natanel](https://sourceforge.net/u/natanel/)** wrote on [Friday, January 18, 2008](https://sourceforge.net/p/freertos/discussion/382005/thread/f5cb7b18/#0b75/8fed):

mistake in my post still have a problem