msp430g2553 Timer 1 vs Timer 2 for frequency input

You're right, on the 20 pin package, not all of the possible output and input signals are available. TA1CLK is one of them, and so is P3. You can't have a low pin count and many signals together.

However, using TA1CLK isn't the only way to count pulses. Depending on pulse frequency, you may set up TA1CCR1 (or even TA0CCR1) for triggering an interrupt on a pulse. And count in software. Then you can use TimerA1 for it main purpose: timing. E.g. for checking the number of pulses during a certain interval (gives the frequency).
Whole P1 and P2 are also capable of triggering an interrupt on an incoming edge.

My highest frequency is about 20KHz which should be fine using interrupts I think.  But I didn't think I could have 2 simultaneous interrupts in software, which is what would happen if  I sent the same signal to two pins (which will often happen).  I'll try the method you described and see how it works.  Any other thoughts, please let me know.  Thanks.

Eugene

Hey it works!  Here's a bit of my code.  I have two pwm outputs and when I send the same pwm output into P1.0 and P1.3 I get two identical increasing counts on the display.  I thought one interrupt would prevent a second interrupt that happens at the same time.  I did read a section in the manual that describes how the chip stores up interrupts and takes care of them next chance it gets.  Makes me wonder how many interrupt it can handle at the same time.  8 maybe?  That would be I could have 8 independent count inputs, which would be fantastic.  Although 4 count inputs would be more that enough.  I've been learning from this e2e blog for a few months now.  It's fun to finally be at a point where I can actually ask an intelligent (so I think) question and maybe even contribute something.  Thanks a bunch for your help.  I'll have to test this further to see what the limitations are, but so far so good.

void main(void)
{
BCSCTL1 = CALBC1_1MHZ;
DCOCTL = CALDCO_1MHZ;
n1=0;
n2=0;
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

InitializeLcm();

ClearLcmScreen();

// ---------------2 pwm section--------
P2DIR |= BIT1; // Set P2.1 to output direction
P2SEL |= BIT1; // P2.1 to TA1.1
P2DIR |= BIT4; // Set P2.4 to output direction
P2SEL |= BIT4; // P2.4 to TA1.2

TA1CCR0 = 4850-1; // PWM Period
TA1CCTL1 = OUTMOD_7; // CCR1 reset/set
TA1CCTL2 = OUTMOD_7; // CCR2 reset/set
TA1CCR1 = 40; // CCR1 PWM duty cycle
TA1CCR2 = 50;
TA1CTL = TASSEL_2 + MC_1; // SMCLK, up mode

P1IE |= BIT0; // P1.3 interrupt enabled
P1IES |= BIT0; // P1.3 Hi/lo edge
P1IFG &= ~BIT0; // P1.3 IFG cleared

P1IE |= BIT3; // P1.3 interrupt enabled
P1IES |= BIT3; // P1.3 Hi/lo edge
P1IFG &= ~BIT3; // P1.3 IFG cleared

_BIS_SR(GIE); // general interrupt enable
// ------------------------------------------
}

void printstuff()
{
itoa(n1,num1,20000);
SendByte(0x80 | 0, FALSE);
PrintStr("Channel 1");
SendByte(0x80 | 0x40, FALSE);
PrintStr("Channel 2");
}

// Port 1 interrupt service routine
#pragma vector=PORT1_VECTOR
__interrupt void Port_1(void)
{
if ( (P1IFG & BIT0) == BIT0 )
{
P1IFG &= ~BIT0; // P1.3 IFG cleared
printstuff();
n1++;
itoa(n1,num1,20000);
SendByte(0x80 | 0x0B, FALSE);
PrintStr(" ");
PrintStr(num1);
}
if ( (P1IFG & BIT3) == BIT3 )
{
P1IFG &= ~BIT3;
printstuff();
n2++;
itoa(n2,num1,20000);
SendByte(0x80 | 0x4B, FALSE);
PrintStr(" ");
PrintStr(num1);
}
}

Looks like I've got some homework to do!  My previous code is sending data to display after each interrupt which is causing incorrect pulse count.  I'm testing at about 200Hz, but counts on the display are increasing at a rate much slower that 200Hz.  So I made a code change to only display counts when counts reach 200.  Now I'm seeing: 200, 1 second later, 400, 1 second later, 800, etc.  Which is 200Hz.  But again, I need to better understand your interrupt explanation to do things right.  Thanks for the advice and the link to priority encoder info.  I'll click the yes-this-answered-my-question button when I see it again.

Eugene

Eugene said:

Looks like I've got some homework to do!  My previous code is sending data to display after each interrupt which is causing incorrect pulse count.  I'm testing at about 200Hz, but counts on the display are increasing at a rate much slower that 200Hz.  So I made a code change to only display counts when counts reach 200.  Now I'm

 Hi, Hint from Jean are the first step, to avoid pulse missing or averaging or some other must be done on foreground loop so:

 On interrupt read the pulse value do some small calculation then store to a queue

 On main loop retrieve the values from queue, do presentation calculations then send to display at a low data rate, human can read few value a second so 200 readings to seconds are too fast  to be presented to eye and just some fraction of them can be appreciated.

Hi Roberto,

Thanks for the good advice.  I was just realizing I need to keep code in the interrupt routine as small as possible.  Then, as you said, I'll display the incrementing value on the display at a reasonable rate to view.  No need to post every increment.  I'll post my results when I get it working.

Thanks,

Eugene

 Hi Again, I edited the previous text to add two missed word and some missing letters.

 TO help time keep write a timing service or add on pwm regular timer interrupt a count down you can use to do action on main loop. Enter LPM on main and exit LPM when timer is fired.

EXAMPLE:

-------------------------------------

volatile int mytimer0=0;

------------ usage on some part of code ----------------

// init timer to value and usage (not on loop that test it !!!)

mytimer=xxx;

if(!timer)

  action@timeout

------------------------------------------------

---- on loop where you need ----

 if( !mytimer)

{

// your code to be executed when timer expire

 mytimer=xxx; // reinit timer if regular service needed

}

enter LPM if needed

---- end loop -----

--------- On interrupt service ------

if(mytimer) mytimer--;

exit LPM if used...

------------------------------------------------------------------------

 This way you can save a lot of time and also enter low power with precise timing.