PBP projects for R/C models

[ScaleRobotics]

For pulse width measurement, I ran across an interesting page.

http://www.mcmanis.com/chuck/robotic...e_measure.html

I borrowed a little bit of the code, and then added it to some DT_Interrupts. I am just measuring a servo pulse width, and sending raw tmr1 result to the serial port here, but you can change it to make it do other things. This was done with a PIC18f2520 in a LAB-X2. But the above gentleman used a PIC16F628, so it should be pretty flexible if you chose the corresponding DT_INTS include file. I would like to see more examples of pulse width measurement as well as pulse generation using interrupts, so if you have some, please share!

DEFINE OSC 20
DEFINE LOADER_USED 1         
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_CLROERR 1 ' Clear overflow automatically
DEFINE HSER_SPBRG 42  ' 115200 Baud @ 20MHz, 0.94%
SPBRGH = 0
BAUDCON.3 = 1         ' Enable 16 bit baudrate generator

LED0 VAR portb.0
LED1 VAR portb.1
LED2 VAR portb.2

adcon1=15        ;sets all to digital
TRISA=%00000000                         ' Set PORTA  
TRISB=%01110000                         ' Set PortB
TRISC=%10000100                         ' Set PortC bit.2 for input (ccp) and bit.7 for ser input

INCLUDE "DT_INTS-18.bas"  ; Base Interrupt System
INCLUDE "sub16.inc"       ; subtract 16 bit macro
                   
LED0=0
LED2=0

risetime VAR WORD
falltime VAR WORD
falltime_l VAR falltime.Byte0
falltime_h VAR falltime.Byte1
risetime_l VAR risetime.Byte0
risetime_h VAR risetime.Byte1

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR0_INT,   ToggleLED0,   ASM,  yes
        INT_Handler    CCP1_INT,   PulseWidth,   ASM,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

T0CON = %10000100
T1CON = %00000001
T2CON = %00111101
CCP1CON = %00000101
@   INT_ENABLE  TMR0_INT      ; Enable Timer 0 Interrupts 
@   INT_ENABLE  CCP1_INT      ; Enable Capture Compare for pulse width measurement

Main:
    PAUSE 1000
    HSEROUT [DEC falltime,10]
GOTO Main

ASM
ToggleLED0
    btg  _LED0        ;blinky light
    INT_RETURN
ENDASM


ASM
PulseWidth
    BTFSS   CCP1CON, CCP1M0 ; Check for falling edge watch
    GOTO    FALL_EDGE       ; Go pick up the falling edge
    MOVF    CCPR1L,W        ; else store leading edge value
    MOVWF   _risetime_l         ; into 16 bit word risetime
    MOVF    CCPR1H,W
    MOVWF   _risetime_h
    BCF     CCP1CON, CCP1M0 ; Now capture the trailing edge
    GOTO    ISR_2           ; Exit the interrupt service routine
        
FALL_EDGE:
    BSF     CCP1CON, CCP1M0 ; Re-set for trailing edge capture
    MOVF    CCPR1L,W        ; Store the captured value into
    MOVWF   _falltime_l         ; falltime_l and ...
    MOVF    CCPR1H,W
    MOVWF   _falltime_h       ;             ... falltime_h
    ;
    ; 16 bit subtract 
    ;     falltime = falltime - risetime
    ;
    SUB16   _falltime, _risetime          ;this subroutine performs 16 bit subtraction
ISR_2
    INT_RETURN
ENDASM