PIC16F84A Tachometer LED routine

[Acetronics2]

Hi, Santa ( de bois )

1) Just the usual gag with PORTA.4 ...

Did you place an external pullup resistor or something to drive the pin to HIGH state ???


2) I note 10 Mhz need a HS Osc ... ( but generally works with XT !!! )


3)

MAIN1:
        PULSIN PORTA.4,0,W1            ' Measure pulse-width in 4µS resolution
        GOTO MAIN

you'd better try

MAIN1:
        RCTIME PORTA.4,0,W1            ' Measure pulse-width in 4µS resolution
        GOTO MAIN

4) your Mathematics are really bad for INTEGERS using ...

W1 = W1 * 4 ' Convert µS to mS
W1 = (60000 / W1) ' Revs in 60 mS
W1 = W1 * 1000 ' Revs in 60 sec

you'd much better use DIV32 ...



That's the first hits ...

Alain

[ThaSanta]

Sorry for letting the problem out (I was kinda tired).

The attached image views the first digit of 4. As if the algorithm doesn't calculate the RPM correct.

1) - I have not yet build the circuit, as I don't have a programmer.
2) - I don't think the Simulator cares about HS or XT :-)

3) I wrote RCTIME instead of PULSIN, but it didn't chance anything.

Actually, after reading the manual to PBP, i don't know how to use DIV32.
I've tried examples, but I still can't figure it out.


- Thanks again guys. :-)