Hi,
Using 16F627A with 4MHz resonator.
I am having lots of issues here I don't know where to start...

Ok I am driving an ultrasonic Transducer from RB3 and RA3
RB3 is sending HWPM to one pin of the Tx and also feeding RA0 (the input of the chip's comparator. The inverted output (RA3) is connected to the other pin of the Tx.

The Rx is on a different circuit, amplified and going through an external comparator and the final output fed into RB0.

Mesurments on the scope is as expected, see bellow:
CH1 is the 40KHz burst lasting 169uS
CH2 is the signal from the Rx showing my sealing at about 6 feet high.
The time scale is 2.5mS
Name: USScope.jpg Views: 445 Size: 36.8 KB

and this is my code:
Code:
@ __config _XT_OSC & _WDT_OFF & _MCLRE_ON & _LVP_OFF & _CP_OFF

DEFINE OSC 4
FLAGS = 0
TRISA = %10111
TRISB = %00000001  
CMCON = %110
;T1CON.0=1               ; Start timer1
;INTCON = %10011000
TMR1H = 0:TMR1L = 0

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

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    INT_INT,  _SignalDetect,   PBP,  yes
        INT_Handler   TMR1_INT,  _SignalTimeOut,   PBP,  yes

    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

;@   INT_ENABLE   INT_INT     ; enable external (INT) interrupts
;@   INT_ENABLE  TMR1_INT     ; Enable Timer 1 Interrupts 


;-------------------temp lcd display ----------------------------
LCD_DB4     VAR PORTB.4      ; Set port for 4 bits bus
LCD_DB5     VAR PORTB.5
LCD_DB6     VAR PORTB.6
LCD_DB7     VAR PORTB.7
LCD_RS      VAR PORTB.2      ; Set RS bit port
LCD_E       VAR PORTB.1      ; Set Enable bit port
LCD_Lines     CON 2          ; # of Lines on LCD,  1 or 2 (Note: use 2 for 4 lines)
LCD_DATAUS    CON 50         ; Data delay time in us 
LCD_COMMANDUS CON 2000       ; Command delay time in us 
INCLUDE "LCD_AnyPin.pbp"     ; Must go after LCD initialization 
Pause 500: LCDOUT $FE,1: pause 250   
LCDOUT $FE,$80,"Display test OK"
;------------------------lcd-------------------------------------- 

Goto main 

Main:
    hpwm 1, 127,40000       ;   Send burst, Ch1, D.Cycle50%, Freq 40Khz
    pauseus 169             ;   length of burst.
    CCP1CON = 0             ;   Stop sending HPWM
    pauseus 950             ;   To prevent Rx from picking up local burst 
    pause 60
goto main

'---[INT - interrupt handler]-------Got Signal within 60mS
SignalDetect:
@ INT_DISABLE INT_INT
@ INT_DISABLE TMR1_INT
    LCDOUT $FE,$C0,dec TMR1H,"    "
    pause 500
@ INT_ENABLE INT_INT
@ INT_ENABLE TMR1_INT
@ INT_RETURN

'---[TMR1 - interrupt handler]------TMR1 Overflow, got no signal
SignalTimeOut:
@ INT_DISABLE INT_INT
@ INT_DISABLE TMR1_INT
    LCDOUT $FE,$C0,"No Signal"
    pause 500
    LCDOUT $FE,$C0,"         "    
@ INT_ENABLE INT_INT
@ INT_ENABLE TMR1_INT
@ INT_RETURN

end
If I REM-out INT_INT or TMR1_INT I endup getting either nothing on the scope orthe HPWM burst is nonstop. For one thing I know I have to somehow define the 60mS timeout for TMR1 but I can't figure it out.

To make a long story short, I would like to accomplish 2 things:
1 - Use INT_INT to pick up the signal from the Rx at RB0 and calculate the distance based on TMR1.
2 - If I get no signal after 60mS I would like to use TMR1_INT to display a different mesage.

I think my code looks simple but obviously too good to be true.

Hopefully someone can help.

Thanks

Mike