Global Triggered timer.

Posted on June 27, 2012 at 13:30

What frequency will this clock have?

You could calibrate it against the master clock using a TIMer, but you're not in a good position to adjust the clock.

If it is data related you could use SPI or Synchronous serial.

You could use the HSE input (OSC_IN) to provide all boards with a common clock.

If you have Ethernet consider if IEEE1588 helps you.

Posted on June 27, 2012 at 14:48

Hi thanks again  for your reply.

fine, i am using all of my board with STM32F107VC 

its not data related just i want to send Ack to all board to start task. This task should start at exact same time of all board.  

if any one board have different frequency then master should reset it at equal interval.

or all board can work with some one reference frequency or clock.

as i use same type of MUC there will be really difference in this clock or freq?... or may be slight change?

Posted on June 27, 2012 at 17:21

You could send the start signal with a pin.

All independent clocks will drift away from each other over time. How fast they drift, and how quickly the bias accumulates will depend on the quality, age, temperature, etc of the source.

Clock stability is often specified in ppm (parts per million) or ppb (parts per billion).

CAN specifies 0.5% accuracy, the internal RC source is not good for this, or USB applications.

For time-of-day time applications you could periodical discipline the assorted boards. There is not a huge opportunity for you to calibrate and correct the external sources, for the LSI and LSE you can tune the prescaler, but that might be a bit too course.

Keeping thing synchronized with software should be achievable in the sub-millisecond range.

The only way to assure they are all in lock step here is to supply a common clock source.

Posted on June 27, 2012 at 19:00

This task should start at exact same time of all board

 

sounds like bad design

the easy way to keep processors in synch clockwise would be to use an external oscillator, but you would still, while the clock would be synchronous, very likely have execution glitch.

Erik

Posted on June 28, 2012 at 15:06

Hi,

i look in to IEEE 1588 so i plan to do some thing like that but all the board should be controlled with master board.

so what type of communication or which will be better to use?

as you people said before can you give me more detail for common oscillator.. how it can be achieved? 

which type will support real time? or better for real time?

thanks..

Posted on June 29, 2012 at 23:13

Do any one have some idea?...

 

What clock/timebase are we talking about, and how accurately do they need to be synchronized.

For a RTC, you could presumably generate a 1PPS and lock slave boards to that.

You could also measure your local clocks wrt to another reference.

http://www.google.com/search?q=time+transfer