ARM上怎么用 gettimeofday 函数

What I usually do, is to have a timer running at 1khz, so it will generate an interrupt every millisecond, in the interrupt handler I increment a global var by one, say ms_ticks then do something like:

volatile unsigned int ms_ticks = 0;void timer_isr() { //every ms    ms_ticks++;}void delay(int ms) {    ms += ms_ticks;    while (ms > ms_ticks)        ;}
It is also possible to use this as a timestamp, so let's say I want to do something every 500ms:
last_action = ms_ticks;while (1) {  //app super loop    if (ms_ticks - last_action >= 500) {        last_action = ms_ticks;        //action code here    }    //rest of the code}
Another alternative, since ARMs are 32bits and your timer will probably be a 32bits one, is to instead of generating a 1khz interrupt, you leave it free running and simply use the counter as your ms_ticks.
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answered Aug 10 '11 at 1:01Vinicius Kamakura6,1761535

Use one of the timers in the chip...

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answered Aug 10 '11 at 3:26old_timer38.4k548101

What you need to do is create your own _gettimeofday() function to get it to link properly. This function could use the appropriate code to get the time for your processor, assuming you have a free-running system timer available.

#include <sys/time.h>int _gettimeofday( struct timeval *tv, void *tzvp ){    uint64_t t = __your_system_time_function_here__();  // get uptime in nanoseconds    tv->tv_sec = t / 1000000000;  // convert to seconds    tv->tv_usec = ( t % 1000000000 ) / 1000;  // get remaining microseconds    return 0;  // return non-zero for error} // end _gettimeofday()
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answered Jul 8 '14 at 18:43JonS14911

You could use the performance timer as shown in the accepted answer of this question...

How to measure program execution time in ARM Cortex-A8 processor?

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answered Aug 10 '11 at 0:59Skyler Saleh3,1911433

It looks like you are using the Econotag which is based on the MC13224v from Freescale.

The MACA_CLK register provides a very good timebase (assuming the radio is running). You can also use the the RTC with CRM->RTC_COUNT. The RTC may or may not be very good depending on if you have an external 32kHz crystal or not (the econotag does NOT).

e.g. with MACA_CLK:

uint32_t t;t = *MACA_CLK;while (*MACA_CLK - t > SOMETIME);
See also the timer examples in libmc1322x:
http://git.devl.org/?p=malvira/libmc1322x.git;a=blob;f=tests/tmr.c
Alternate methods are to use etimers or rtimers in Contiki (which has good support for the Econotag). (see http://www.sics.se/contiki/wiki/index.php/Timers )
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edited Aug 5 '12 at 15:17Spudley121k29163248
answered Aug 5 '12 at 2:32Mariano Alvira20613

I've done this before in one of my applications. Just use :

while(1){...}

What I usually do, is to have a timer running at 1khz, so it will generate an interrupt every millisecond, in the interrupt handler I increment a global var by one, say ms_ticks then do something like:

volatile unsigned int ms_ticks = 0;void timer_isr() { //every ms    ms_ticks++;}void delay(int ms) {    ms += ms_ticks;    while (ms > ms_ticks)        ;}
It is also possible to use this as a timestamp, so let's say I want to do something every 500ms:
last_action = ms_ticks;while (1) {  //app super loop    if (ms_ticks - last_action >= 500) {        last_action = ms_ticks;        //action code here    }    //rest of the code}
Another alternative, since ARMs are 32bits and your timer will probably be a 32bits one, is to instead of generating a 1khz interrupt, you leave it free running and simply use the counter as your ms_ticks.
shareimprove this answer
answered Aug 10 '11 at 1:01Vinicius Kamakura6,1761535

Use one of the timers in the chip...

shareimprove this answer

answered Aug 10 '11 at 3:26old_timer38.4k548101

What you need to do is create your own _gettimeofday() function to get it to link properly. This function could use the appropriate code to get the time for your processor, assuming you have a free-running system timer available.

#include <sys/time.h>int _gettimeofday( struct timeval *tv, void *tzvp ){    uint64_t t = __your_system_time_function_here__();  // get uptime in nanoseconds    tv->tv_sec = t / 1000000000;  // convert to seconds    tv->tv_usec = ( t % 1000000000 ) / 1000;  // get remaining microseconds    return 0;  // return non-zero for error} // end _gettimeofday()
shareimprove this answer
answered Jul 8 '14 at 18:43JonS14911

You could use the performance timer as shown in the accepted answer of this question...

How to measure program execution time in ARM Cortex-A8 processor?

shareimprove this answer

answered Aug 10 '11 at 0:59Skyler Saleh3,1911433

It looks like you are using the Econotag which is based on the MC13224v from Freescale.

The MACA_CLK register provides a very good timebase (assuming the radio is running). You can also use the the RTC with CRM->RTC_COUNT. The RTC may or may not be very good depending on if you have an external 32kHz crystal or not (the econotag does NOT).

e.g. with MACA_CLK:

uint32_t t;t = *MACA_CLK;while (*MACA_CLK - t > SOMETIME);
See also the timer examples in libmc1322x:
http://git.devl.org/?p=malvira/libmc1322x.git;a=blob;f=tests/tmr.c
Alternate methods are to use etimers or rtimers in Contiki (which has good support for the Econotag). (see http://www.sics.se/contiki/wiki/index.php/Timers )
shareimprove this answer
edited Aug 5 '12 at 15:17Spudley121k29163248
answered Aug 5 '12 at 2:32Mariano Alvira20613

I've done this before in one of my applications. Just use :

while(1){...}