# TIMER0\_OVF and TIMER2\_OVF **URL:** \ **Category:** Kernel\ **Created:** [February 1, 2008, 2:21pm UTC](https://forums.freertos.org/t/timer0-ovf-and-timer2-ovf/2164 "2008-02-01T14:21:24Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\ **Post date:** [February 1, 2008, 2:21pm UTC](https://forums.freertos.org/t/timer0-ovf-and-timer2-ovf/2164/1 "2008-02-01T14:21:24Z")
**[brenodee](https://sourceforge.net/u/brenodee/)** wrote on [Friday, February 01, 2008](https://sourceforge.net/p/freertos/discussion/382005/thread/61a63ebf/#fa3b): Hi all, I’m tried to use the interruption from Timer2\_ovf and Timer0\_ovf an atmega128 but it doesn’t work out. The INT0 and INT1 vector work fine. I’m posting my code so that you could figure out. #include \ #include \ #include \ #ifdef GCC\_MEGA\_AVR     /\* EEPROM routines used only with the WinAVR compiler. \*/     #include \ #endif /\* Scheduler include files. \*/ #include "FreeRTOS.h" #include "task.h" #include "croutine.h" #include "semphr.h" #include \ #include \ #include \<…/…/Source/include/semphr.h\> #include \ /\* Demo file headers. \*/ #include "PollQ.h" #include "integer.h" #include "serial.h" #include "comtest.h" #include "crflash.h" #include "print.h" #include "partest.h" #include "regtest.h" #define SIGNAL    \_\_attribute\_\_ ((signal)) /\* Baud rate used by the serial port tasks. \*/ #define mainCOM\_TEST\_BAUD\_RATE            ( ( unsigned portLONG ) 38400 ) void TIMER0\_OVF(void)\_\_attribute\_\_ ((signal,naked)); void vApplicationIdleHook( void ); /\*-----------------------------------------------------------\*/ portSHORT main( void ) {     /\* Registers \*/     SREG  = 0x80;     MCUCR = 0x03;     EICRA = 0x0F;     EIMSK = 0x03;     TIMSK = 0x01;     TCCR0 = 0x03;         xSerialPortInitMinimal( mainCOM\_TEST\_BAUD\_RATE, 1 );     vParTestInitialise();         while(1);     return 0; } /\*-----------------------------------------------------------\*/ ISR(TIMER0\_OVF\_vect) // INT\_0 or INT\_1 work out!!! {     vParTestToggleLED( 1);         vParTestInitialise(); } void vApplicationIdleHook( void ) {     vCoRoutineSchedule(); } Thanks, for all!!!! ---
**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\ **Post date:** [February 1, 2008, 7:40pm UTC](https://forums.freertos.org/t/timer0-ovf-and-timer2-ovf/2164/2 "2008-02-01T19:40:10Z")
**[woops\_](https://sourceforge.net/u/woops_/)** wrote on [Friday, February 01, 2008](https://sourceforge.net/p/freertos/discussion/382005/thread/61a63ebf/#fa3b/d075): Dont know the answer but dont think it is anything todo with FreeRTOS so must just be in the register settings. Are there examples in the compiler to copy? ---
**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\ **Post date:** [February 1, 2008, 8:55pm UTC](https://forums.freertos.org/t/timer0-ovf-and-timer2-ovf/2164/3 "2008-02-01T20:55:49Z")
**[jaydmdigital](https://sourceforge.net/u/jaydmdigital/)** wrote on [Friday, February 01, 2008](https://sourceforge.net/p/freertos/discussion/382005/thread/61a63ebf/#fa3b/7eba): See my thread here [https://sourceforge.net/forum/forum.php?thread\_id=1882976&forum\_id=382005](https://sourceforge.net/forum/forum.php?thread_id=1882976&forum_id=382005) The default is for Timer1 not 0 or 2 (8-bit) or 3(second 16-bit timer) If you want to change it, you need to modify the port.c file …\FreeRTOS\Source\portable\GCC\ATMega323 #define portCOMPARE\_MATCH\_A\_INTERRUPT\_ENABLE    ( ( unsigned portCHAR ) 0x10 ) //set it to the correct interrupt mask for TIMER3 if you like /\* \* Setup timer 1 compare match A to generate a tick interrupt. \*/ static void prvSetupTimerInterrupt( void ) { unsigned portLONG ulCompareMatch; unsigned portCHAR ucHighByte, ucLowByte;     /\* Using 16bit timer 1 to generate the tick.  Correct fuses must be     selected for the configCPU\_CLOCK\_HZ clock. \*/     ulCompareMatch = configCPU\_CLOCK\_HZ / configTICK\_RATE\_HZ;     /\* We only have 16 bits so have to scale to get our required tick rate. \*/     ulCompareMatch /= portCLOCK\_PRESCALER;     /\* Adjust for correct value. \*/     ulCompareMatch -= ( unsigned portLONG ) 1;     /\* Setup compare match value for compare match A.  Interrupts are disabled     before this is called so we need not worry here. \*/     ucLowByte = ( unsigned portCHAR ) ( ulCompareMatch & ( unsigned portLONG ) 0xff );     ulCompareMatch \>\>= 8;     ucHighByte = ( unsigned portCHAR ) ( ulCompareMatch & ( unsigned portLONG ) 0xff );     OCR1AH = ucHighByte;     OCR1AL = ucLowByte; //Change to OCR3AH and AL     /\* Setup clock source and compare match behaviour. \*/     ucLowByte = portCLEAR\_COUNTER\_ON\_MATCH | portPRESCALE\_64;     TCCR1B = ucLowByte; // Make sure the correct register for TIMER3     /\* Enable the interrupt - this is okay as interrupt are currently globally     disabled. \*/     ucLowByte = TIMSK;     ucLowByte |= portCOMPARE\_MATCH\_A\_INTERRUPT\_ENABLE;     TIMSK = ucLowByte; } too bad no way to mark up my comments Jay