2009-05-30 12:36:10     How to make a high precision timer in linux

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2009-05-30 12:36:10     How to make a high precision timer in linux

yacobi chen (CHINA)

Message: 74821   

 

I want to get a 10kHz PWM in one of BF527 GPIOs.

 

All the 8 timers in BF527 are configured to other usage. So I have to use the general timer supported by linux kernel.

 

The timer precision is decided by system tick, which is up to 1/1000 second.

 

So, how can I get a high precision timer? I don't want to change the parameter HZ in system.

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2009-05-30 13:02:27     Re: How to make a high precision timer in linux

Robin Getz (UNITED STATES)

Message: 74822   

 

Yacobi:

 

I'm not sure it is practical - is 10kHz the slowest thing you are using all the timers for?

 

-Robin

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2009-05-30 23:44:17     Re: How to make a high precision timer in linux

yacobi chen (CHINA)

Message: 74829   

 

Thank you Robin.

 

The requisite frequence can be reduced to 500Hz. So kernel timer can fit this work, I think.

 

By the way, It is no way to get a high precision timer without the 8 timers supported by BF527. Is that right?

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2009-05-31 02:31:10     Re: How to make a high precision timer in linux

Sonic Zhang (CHINA)

Message: 74831   

 

Yes, unless you adapt an external timer device to the system bus or GPIO.

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2009-05-31 04:26:37     Re: How to make a high precision timer in linux

yacobi chen (CHINA)

Message: 74873   

 

I am wondering about the timers in blackfin(BF527).

 

If I configure a GPIO to other usages rather than timer, can I use the corresponding timer to count ticks?

 

For example, I configure PG11 to HOST_WR, can I use timer7 to count?

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2009-05-31 07:38:43     Re: How to make a high precision timer in linux

Robin Getz (UNITED STATES)

Message: 74875   

 

Yacobi:

 

Yes - but you will need to write a custom GPIO handler - if you want to use the existing things - the lactency of the entire system would make it too slow.

 

-Robin

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