CCP Tacho

[umka]

i want to be able determine the speed of a motor and have been reading old tacho post.

is the CCP in capture the best/easiest way to do this?

when using the CCP in CCP_CAPTURE_RE mode, will out put the number of clock cycles between its last rising edge and the current one?

does one need to reset the timer when the code has been into the isr

is this all the code needed where rise is the number of clock cycles?

[PCM programmer]

Study this thread while looking at the PIC data sheet and see how
the code works.
http://www.ccsinfo.com/forum/viewtopic.php?t=29963

[gjs_rsdi]

sorry just now, the bellow works.
setup_timer_3(T1_INTERNAL|T1_DIV_BY_8);
setup_ccp1(CCP_CAPTURE_FE);//used for RPM monitoring
can be also RE.
the controller runs at 32MHz (18F252)
//RPM.h is the rpm reading header
//to capture the rpm, timer1 with prescaller 1:8 is used, to get 1us
// resolution.
//with ccp1 capture unit
//timer1 increment is 1us
//timer1 overflow is 65.536ms
//1,000ms/65.536=15.259 RPS
//15.259*60=915.5 RPM minimum (two stroke engine will not run lower
//than 1500 RPM
//example:
//(1,000,000us/6,000)*60=10,000 RPM
//if CCP_1<6,000, rpmtime=6,000
//the rpm calculations for hold and report are made in rpm_isr under main
#int_TIMER3
void TIMER3_isr(void)
{
rpmtime=0;//RPM<915.5, no rpm/engine not running
}
#int_CCP1
void CCP1_isr(void)
{
set_timer3(0);
clear_interrupt(INT_CCP1);
rpmtime=CCP_1;
CCP_1=0;
}
under main
while(1)//warning "Condition always TRUE" /the program will
//run in "while" if no interrupt occured
{
restart_wdt();
enable_interrupts(GLOBAL);
rpm_isr();
}
if something not clear, email [email protected]
joseph