Incoming Pulse Monitoring code - comments and suggestions welcome

[Darrel Taylor]

Hi jamie,

It's nice to see more examples with Instant Interrupts popping up.

I think using the CCP to generate an interrupt on every transition of the Input is slowing things down.

If you handle the "Input to Inverted Output" in the main loop, It should go alot faster than 2khz.
Then the interrupts can just handle the timer overflows.

Here's a possibility ...

'------------------------------------------------
'  	Pulse Monitor
'  	PIC16F628A @ 4mhz
'
'
'	Input Signal Port B.3
'	Output Signal Port B.5
'------------------------------------------------


INCLUDE "DT_INTS-14.bas"        ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"        ' Include if using PBP interrupts


CMCON = 7                       ' set portA to digital
TRISA = %00100000               ' Port A all output but MCLR
TRISB = %00001000               ' Port B all output but 3 (CCP)
T1CON = %00110000               ' Set Timer 1, Off and 1/8 prescale (fire every 520ms)
T2CON = %00000011               ' Set Timer 2, Off and 1/16 prescae (fire every 4ms)
T1count     VAR BYTE            ' Timer 1 count (1 count = 0.52 sec)
i           VAR BYTE            ' i is the incrementer for the pulse generator

InPIN       VAR PORTB.3         ' Input Pin
OutPIN      VAR PORTB.5         ' Output Pin
TMR1ON      VAR T1CON.0
TMR2ON      VAR T2CON.2
LastState   VAR BIT

ASM
INT_LIST  macro     ; IntSource,      Label,   Type, ResetFlag?
        INT_Handler    TMR1_INT,   _nospeed,    PBP,    yes
        INT_Handler    TMR2_INT,  _generate,   	PBP,    yes
    endm
    INT_CREATE                  ; Creates the interrupt processor

    INT_ENABLE   TMR1_INT       ; enable timer1 interrupts (CCP timer)
    INT_ENABLE   TMR2_INT       ; enable timer2 interrupts (pulse generator)
ENDASM


Low OutPIN                      ' start with Output LOW
T1count = 0                     ' set variable	
TMR1H   = 0                     ' Clear high byte of TMR1 counter
TMR1L   = 0                     ' Clear low byte
i       = 0                     ' set variable
TMR1ON  = 1                     ' Turn TMR1 on here

   
'=======================================================================================
'---[MainLoop handles the Inverted transfer From InPIN to OutPIN] ----------------------
MainLoop:
    if InPIN <> LastState then  ' If Input State Changed 
        LastState = InPIN
        TMR2ON = 0              ' Stop Timer 2
        OutPIN = LastState ^ 1  ' Output = inverted state of Input
        TMR1H = 0               ' Clear high byte of TMR1 counter
        TMR1L = 0               ' Clear low byte
        T1count = 0
    endif
GOTO MainLoop
    
'=======================================================================================
'---[TMR1 - interrupt handler - Called when Timer1 Overflows @ 520ms] ------------------
nospeed:
    T1count = T1count + 1       ' increment every 520ms

    If T1count >= 3 then        ' no pulses for 1560ms, start generating them
        TMR2ON = 1              ' Set Timer 2 on
        T1count = 0             ' reset the TMR1 count
    endif
@ INT_RETURN

'==========================================================================================
'---[TMR2 - interrupt handler - This will fire every 4.103ms]------------------------------
' send a 20ms pulse every  (12 * 4ms) 48ms, gives a frequency of ~ 15hz
generate:
    i = i + 1                   ' increment tmr2 count

    if i < 12 then              ' Pin is low for 1-11
        OUTPIN = 0
    else
        OutPin = 1              ' Pin is high for 5 ints  (20ms)
    endif
    If i = 17 then i = 0        ' restart cycle, total = 69.751ms = 14.3hz 
@ INT_RETURN