Hello.
I want to measure input pulse duty using timer capture mode on MSP430FR5849.
Max Frequency will be 1MHz and pin assign is P1.2
When I tested the function, I could get a steady value to 500 KHz. However, in the case of 1MHz, I could not get a steady value.
Below is my source code. Please let me know how can I measure 1MHz input frequency.
Thank you.
===============================================================================================
/*
* main.c
*/
#include "main.h"
unsigned int gap_buf[50];
unsigned char index = 0;
unsigned int new_tmr = 0;
unsigned int old_tmr = 0;
unsigned int new_tmr1[50];
unsigned int old_tmr1[50];
void Init_Timer0_A0(void);
int main(void)
{
WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer
PJOUT = 0;
PJSEL0 = BIT4 | BIT5; // For XT1
PJDIR = 0xFFFF;
PM5CTL0 &= ~LOCKLPM5; //GPIO Wake up
// Configure one FRAM waitstate as required by the device datasheet for MCLK
// operation beyond 8MHz _before_ configuring the clock system.
FRCTL0 = FRCTLPW | NWAITS_1;
// Clock System Setup
CSCTL0_H = CSKEY >> 8; // Unlock CS registers
CSCTL1 = DCORSEL | DCOFSEL_4;
CSCTL2 = SELA__VLOCLK | SELS__DCOCLK | SELM__DCOCLK; // Set SMCLK = MCLK = DCO,
// ACLK = VLOCLK
CSCTL3 = DIVA__1 | DIVS__1 | DIVM__1;
CSCTL0_H = 0; // Lock CS registers
P1SEL0 |= BIT2;
P1SEL1 &= ~BIT2;
Init_Timer0_A0();
__bis_SR_register(GIE);
while(1)
{
}
return 0;
}
void Init_Timer0_A0(void)
{
TA1CTL = TASSEL__SMCLK + MC__CONTINUOUS; // SMCLK, contmode
TA1CCTL1 =CM_1+CCIS_0+CAP+CCIE+SCS;
TA1CTL &=~TAIFG;
return;
}
#pragma vector = TIMER1_A1_VECTOR
__interrupt void Timer1_A1_ISR(void)
{
if(TA1CCTL1 & CCI)
{
new_tmr = TA1CCR1;
gap_buf[index] = new_tmr - old_tmr;
index++;
if(index >= 50)
{
_no_operation();
index = 0;
}
old_tmr = new_tmr;
TA1CCTL1 &= ~CCIFG;
TA1CCR1 = 0;
}
}
