push button S2

I would recommend you start with

• msp430g2xx3_P1_04.c                        P1 Interrupt from LPM4 with Internal Pull-up

from the mentioned code-examples. This shows how to use the interrupt on an input pin. Then look at

• msp430g2xx3_ta_03.c                        Timer_A, Toggle P1.0, Overflow ISR, DCO SMCLK

which uses the timer's overflow interrupt in continuous mode. You can also use that.

Dennis

You want to detect the press on the button to start the timer, that means you want to detect the signal on the pin from high to low level. Then you want to detect the release of the button again, so you want to detect the change from low to high level. That is why you have to change the edge sensitivity for the interrupt.

Look into the user's guide

Page 327 - Digital I/O

Dennis

If lowest possible power consumption is not required, then polling approach is much more easy to implement and understand:

1. Enable P1.3 for input wit pull-up enabled

2. Set periodic timer interrupts, for example WDT in periodic interupt mode, WDT_MDLY_32.

3. In WDT ISR check pin state and count ISR calls measuring for how long pin input is low, such way you will know time of button press:

volatile unsigned int s2counter = 0, flag_s2pressed = 0;

#pragma vector=WDT_VECTOR
__interrupt void watchdog_timer(void)
{
  if (!(P1IN & BIT3)) {
    if (s2counter < 65535)
      if ( ++s2counter > 8 ) // debounce (1/4 sec in case of 32ms tics)
        flag_s2pressed = 1;
  } else {
    s2counter = 0;
    flag_s2pressed = 0;
  }
}

This will allow you to count button press time up-to 2097 seconds.

[disclaimer] Code is not checked, use at your own risk

The timer is 16 bits, so it can count to a maximum of 65535 and then "rolls over" to 0 again. This roll-over can generate an interrupt where you can increment a variable that counts these roll-overs for you. For a long button press the timer might roll over many times. Something must keep track on this. You could also set an easier to calculate value for the timer. If you clock the timer with 1MHz, for example and configure the timer to generate an interrupt every 50,000 clock cycles, then this would mean every 50ms.

Let's say you had 20 interrupts during your button press and the roll-over-variable therefore holds the value 20. Furthermore TAR is 30,000 now. Then your time would be

20 * 50ms = 1s
+
(1 / 1,000,000 Hz) * 30,000 = 30ms
=
1s and 30ms

Dennis

Thanks both of you 

It kinda worked but it still has timer issues which i hope the previous post will solve

thanks for your help once again