I found a BUG in IAR LPC2129 PORT

Kernel
1

nobody wrote on Tuesday, March 21, 2006:

Salam,

in port.c

ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;

That’s wrong cause the clock of the peripherals (include Timer0) is NOT CPU Clock (CCLK) but it’s PCLK.

and

PCLK = CCLK / VBP Divider

At reset for LPC2129 VBP Divider = 4

So The above line must be

ulCompareMatch = (configCPU_CLOCK_HZ /4 ) / configTICK_RATE_HZ;

I found this bug when i was trying to blink a led every second using vTaskDelayUntil

Here is my working code.

static void vTaskCode(void *pvParameters)
{
    portTickType xLastWakeTime;
    const portTickType xFrequency = 1000;
    xLastWakeTime = xTaskGetTickCount();

    for (;:wink: {
         Led_Toggle();
         vTaskDelayUntil( &xLastWakeTime, xFrequency );
    }
}

Bye
Eng. Amr Ahmed
EGYPT

2

nobody wrote on Tuesday, March 21, 2006:

I forgot to mention that configTICK_RATE_HZ must be configure to 1000 in freeRTOSconfig.h to use the above task to blink the led every 1 SEC :slight_smile:

Enjoy
Amr Ahmed
EGYPT

3

nobody wrote on Tuesday, March 21, 2006:

I think, as downloaded, the line should actually be:

ulCompareMatch = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1;

cpu clock being defined to the correect value for the equation.

You change the value or use different hardware?

4

nobody wrote on Tuesday, March 21, 2006:

AS DOWNLOADED THE LINE IS

/* Calculate the match value required for our wanted tick rate. */
ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;

THAT IS NOT RIGHTTTTTTTTTTTT

5

nobody wrote on Tuesday, March 21, 2006:

AS DOWNLOADED

ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;

This is not right !!!

I use Olimex board (LPC2129)

So configCPU_CLOCK_HZ = 14745600 (crystal value)

I didn’t use the PLL.

#define configCPU_CLOCK_HZ            ( ( unsigned portLONG ) 14745600 )

BYE

6

nobody wrote on Tuesday, March 21, 2006:

It is right if you are using the same software and hardware as the demo with no modifications at all.  I know because I can time the LED’s flashing and they are exactly correct.

I think you are making an assumption as to what configCPU_CLOCK_HZ means.  This should be set to the frequency as used by the timer which may but probably will not be the same as some other clocks on the system.

7

nobody wrote on Tuesday, March 21, 2006:

That’s right man.

configCPU_CLOCK_HZ must be the clock of the Timer.

So configCPU_CLOCK_HZ must be

configCPU_CLOCK_HZ = configCPU_CLOCK_HZ / VBP Divider

Please look to the datasheet

Bye
AmR Ahmed
EGYPT