Measure Pulsewidth Input capture QG8

abicash — Thu, 19 Sep 2013 10:00:31 GMT

Hello

I am trying this seemingly effortless task, but am not able to get there.

I am measuring a pulse time of an input pulse on TPM Channel-1. Frequency is 50Hz.

Please see attached code snippets where i initialise the timer.

#define BusFrequency 8MHz

#define TIMER_START 0x4F // bus clk,divide by 128

#define TIMER_OVERFLOW 0xFFFF //maximum

interrupt 6 void Timer1_Capture (void)

{

TPMC1SC = 0; //Clear interrupt , ack interrupt

inputCycleTime[p] = TPMC1V; //get value of TPMC1V at this edge

p++; // increment count for next edge capture

if(p >= 1)

{

inputWidth = inputCycleTime[1]-inputCycleTime[0]; //determine duration

p=0;

TPMC1V =0;

}

TPMC1SC = 0x44; // rising edge initiate

}

void Timer1_init(void)

{

// Timer1 period

TPMMOD = TIMER_OVERFLOW;

TPMC1SC = 0x44; //i/p capture rising edge captures

//0x0c =both edges, 0x08 = falling edges

}

Now i run in all sorts of troubles with above code.I should be able to read 20ms of time = 1250 counts between both rising edges

but i get a varied value unaccounted for.

Can someone throw some light?

Thnks and Regards

Re: Measure Pulsewidth Input capture QG8

abicash — Fri, 20 Sep 2013 08:22:34 GMT

I rectified the mistake.

Problem solved.

Shouldn't have stopped and restarted the channel in ISR