Reading timer counter & prescaler on the fly - STM32F205RBT6

[aamirali641989]

Posted on July 19, 2014 at 13:47

I am using STM32F205RBT6.

I have to start a timer when a particular event happens. This I have done in programming.

After that interrupts comes on three other pins. Now I have to measure the time between:

1. Start & interrupt on pin 1 

2. Start & interrupt on pin 2

3. Start & interrupt on pin 3

1. Can I read the value of counter & timer on the fly so that I can measure time?

2. If answer is yes, then I think there is some error in it. Like when interrupt happens on pin then control will first go to external pin ISR, where I will read timer values. In this error may come ? Can I reduce this error?

3. Is there any better method to do this?

[Tesla DeLorean]

Posted on July 19, 2014 at 14:51

You can read TIMx->CNT, or have the pin transition latch the event in TIMx->CCRx

[aamirali641989]

Posted on July 29, 2014 at 18:42

Thanks clive for your reply.

But I have 3-10 such stop pulses come.

But CCRx register has only one or ttwo pins with it. then what would be best way to do that

[Tesla DeLorean]

Posted on July 29, 2014 at 18:50

Most timers have 4 channels, and can latch events on four pins.

If the counter is free running

Input Capture is the equivalent of

  TIMx->CCRx = TIMx->CNT; // At the event

You can back out the interrupt latency by reading TIMx->CNT in the handler. ie current value, vs value latched at the edge.

For PWM Input mode, or resetting the timer, then you'll likely need one timer per input signal.