Subject:
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wits end with PWM measurement
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 22 Apr 2000 12:53:03 GMT
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Original-From:
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David Young <djyoung@voyager.co.nzSPAMCAKE>
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Viewed:
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1140 times
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Dear All
I'm at my wits end on this one. It's a little routine to measure on PA0 a pulse
width of a PWM signal generated on PA7. The two pins are linked with a jumper.
I've looked through all the books and and handyboard archive, but all I get is
values that just don't seem to make sense.
Can anyone tell me where I'm going wrong.
TIA David young
void main()
{
int period=1500; /* High period for PWM signal on PA7 */
int TIC3 = 0x1014; /* TIC3 at $1014 and $1015 (connected to PA0) */
int TCTL2 = 0x1021; /* TCTL2 (input capture register) at $1021 */
int TFLG1 = 0x1023; /* TFLG1 (input capture flag register) at $1023 */
int rising_edge;
int falling_edge;
servo (period); /* PWM signal on PA7 - connected to PA0 by jumper */
servo_on ();
/* Detect a signal at PA0 on its rising edge -> set bit #0 to 1 and #1 to 0 */
bit_set(TCTL2,0);
bit_clear(TCTL2,1);
bit_set(TFLG1,0); /* Clear TFLG1 */
while (peek(TFLG1) & 0x01 != 0x01){} /* Loop until the capture flag for PA0 is
set*/
/* Get rising edge time in TIC3 */
rising_edge = peekword(TIC3);
/* Detect a signal at PA0 on its falling edge -> set bit #0 to 1 and #1 to 1 */
bit_clear(TCTL2,0);
bit_set(TCTL2,1);
bit_set(TFLG1,0); /* Clear TFLG1 */
while (peek(TFLG1) & 0x01 != 0x01) {} /* Loop until the capture flag for PA0 is
set*/
/* Get falling edge time in TIC3 */
falling_edge = peekword(TIC3);
printf("Pulse range = %d", rising_edge);
printf(" %d\n", falling_edge);
servo_off();
}
--
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