S12 / MagniV MicrocontrollersのトピックRe: to use periodic interrupt timer(PIT)

to use periodic interrupt timer(PIT)

navaneeth_ankam — Sun, 24 Feb 2013 13:58:10 GMT

hi,

i am working on MC9S12XDP512 microcontroller.and i have interfaced with proximity sensor. i have given 5v power supply and i was getting 5v when the obstacle was not present and 0v for when the obstacle was there. my objective is ,,,,,,when the obstacle is present for 2 seconds afterwards the LED should glow. or when there is no obstacle for 2 seconds afterwards also the LED should glow.

so...i have used normal timer programing ...but i am not getting.so is better to use periodic interrupt timer(PIT).

Re: to use periodic interrupt timer(PIT)

navaneeth_ankam — Sun, 24 Feb 2013 14:20:12 GMT

hi,

so...i have used normal timer programing ...but i am not getting.so is better to use periodic interrupt timer(PIT).

Re: to use periodic interrupt timer(PIT)

RadekS — Mon, 25 Feb 2013 16:01:57 GMT

PIT is suited for output compare function only (generate period). I think that it will be difficult to use PIT for measuring of pulse with.

If I understood correctly, your problem with normal timer (ECT) is 2s interval = too long for TCNT timer. Correct?

In attachment you can find simple example code for measuring of pulse width by ECT module. This example code uses overflow interrupt for measuring longer pulses (longer than TCNT period). I suppose that you can simply modify this code for measuring both (0V and 5V) pulses.

You can also simply testing overflow variable for 2s limit in overflow interrupt routine.

Note: There is necessary take into account error of one TCNT period. If you want get better accuracy (of 2s limit), you should calculate with last value of TCx timer/resets TCx timer value….

Re: to use periodic interrupt timer(PIT)

navaneeth_ankam — Tue, 26 Feb 2013 15:32:59 GMT

thank u...radek

i will try with this....and get back you