Stopping Timer A on MSP430

Coding a microcontroller like MSP430 is a lot more difficult (at least for me) than Arduino but since I have a few around, I really want to learn. An important aspect of working with these are interrupts. I looked over the examples and they are all great but I wanted to do something a little bit more yet still simple. The idea: start a timer when the interrupt on a button fires, then stop it after a few seconds, if the button is not pushed again; if it is, restart the timer so it always stops the same time after the last button push. Pretty simple in theory; well, in practice as well after I figured it out. The most difficult task was to restart the timer with each button push. I tried to find info on the web and by reading the MSP430x2xx Family User's Guide but couldn't get anywhere: no matter what I tried the timer was stopping after what seemed like random times (after a lot of debugging I realized it wasn't random, the timer was always stopping after the right time measured since the first button push).

I tried several things but mainly:

set TACCR0=0 - I hoped this will reset the counter to 0 which is not true, and this was spelled out in the doc I mentioned

set TACTL = MC_0 - I hoped that stopping the timer means resetting the counter but it seems that the timer just stopped and when I re-enabled it it continued counting from where it left off.

In the end, re-reading the user's guide for the nth time, I noticed a paragraph in which it says that the register holding the current count (TAR) is writable (I was sure until then that is read only) and this was the key: when I want to reset the counter, I just write 0 in this register; just to make sure all is well, I also reset TACTL just to make sure the timer restarts - this may not be needed but it works so I left the code in there. Another thing is stopping the timer in the timer ISR by doing TACTL = MC_0 because I want the timer to shut down after the given time, and not keep counting - this makes the mcu go back to sleep mode.

The final version I ended up with is here: I am sure it can be improved but again, it works now and exactly the way I wanted it so I'll keep it this way.

Next thing: play with external interrupts.

[Edit] Now that I figured out how to reset the timer, I changed the code to use a variable to handle the restart and stop of the timer: reset it to 0 when the button interrupt fires, increment it in the timer ISR and stop the timer after a few iterations. This is much more flexible because a) I can stop the timer at the exact time I want (not being dependent on the timer counter and the clock frequency and dividers) and b) I can reuse the timer for other things, changing the behavior based on the TAIV vector. Next step in developing my little app will use this approach.