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

[Kenjones1935]

You all posted code specifically for the 12F675. My PIC is a 16F887.

I am at a loss to translate from one PIC to the other. My PBP compiler (set up for 16F887) has no idea what to do with GPIO.x references. When I set it for 12F675 it is happy, but the resulting code is useless to my PICkit2.

Is it my job to read about the 12F675 and try to figure out which register in my 16F887 is equivalent? That would be an excellent homework assignment.

Ken

[tenaja]

Is it my job to read about the 12F675 and try to figure out which register in my 16F887 is equivalent? That would be an excellent homework assignment.

Well, yes... but it will take a whole lot longer to open the file than it will to hit ctrl-f and search for gpio.

[Kenjones1935]

I do not have all the necessary includes. Judging from the code snip offered by scalerobotics I need the base interrupt system for the 16 bit machines.

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

I have a PICkit 2 with a 16F887.
Does a DT_INTS-16.BAS exist? Where?

ken

[ScaleRobotics]

I do not have all the necessary includes. Judging from the code snip offered by scalerobotics I need the base interrupt system for the 16 bit machines.

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

I have a PICkit 2 with a 16F887.
Does a DT_INTS-16.BAS exist? Where?

ken

Hello Ken,

The DT_INTS-14.bas covers the PIC16 devices. The newest version 1.00 can be found here (at botom left). http://darreltaylor.com/DT_INTS-14/intro2.html The code should be able to be modified for your chip, but there are PIC chips with more timers, and more ccp pins out there.

It might be best to try out some of the ready made samples that Darrel gives, just to get the hang of using his interrupts, and making sure your includes, and configs are working.


I am working on a DT_INTS based RC servo passthrough (servo pulse measurement and pulse generation, but it is a little jittery right now, so I have try to trouble shoot that.

[Kenjones1935]

Mr or Ms scalerobotics,

My original idea for an RC car that could toggle between RC control and autonomous control was to have DPDT relays switching between the RC receiver PWM outputs and the PIC PWM outputs. Please see:

http://www.ziplink.net/users/kjones/...color_copy.jpg

I discounted the idea of routing the RC commands through the PIC as that route might be slow and/or noisy. It sounds like that is exactly what you are designing. Please keep me in touch with your progress.
I think that design would force me to choose another PIC as it would require three inputs from the radio receiver and two outputs to the electronic speed control and the steering servo. -- all interrupt driven I would think.

I am sort of stuck with the PICkit 2 since I have purchased three of them. They are also not toooo big. If I could get more confidence prototyping I might consider building my own PIC carrier, but just getting the prototyping bits, parts and pieces entails an hour's drive to a store with which I am not familiar.

Ken

[ScaleRobotics]

Hey Ken, OK, now I understand your project, and the use of the PicKit's!

Well, I was able to correct my servo jitter, an error on my part of course.

Here is some code for a single servo channel pass through, using DT_INTS. Next I will try adding the other CCP pin.

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
halftime_bit var bit
adcon1=15               ;sets all to digital
TRISA=%00000000         ' Set PORTA  
TRISB=%01110000         ' Set PortB switch inputs (not used)
TRISC=%10000100         ' Set PortC.2 to input for ccp1
                        ' set portC.7 to input for serial port

INCLUDE "DT_INTS-18.bas"  ; Base Interrupt System
include "sub16.inc"       ; subtract 16 bit macro

LED1=1                    ; Set to Output Low
LED0=0
led2=1
portb.3 = 0
servo_out var portb.3

risetime var word      ;used for pulse width measure start of pw
falltime var word      ;time at end of pulse width
timer0 var word        ;used to load tmr0l and h bytes
falltime_l var falltime.byte0
falltime_h var falltime.byte1
risetime_l var risetime.byte0
risetime_h var risetime.byte1


pause 1000
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        ;INT_Handler   TMR1_INT,   ToggleLED1,   ASM,  yes
        INT_Handler   TMR0_INT,     _PWMout,      ASM,  yes
        INT_Handler   CCP1_INT,      PWMeasure,   ASM,  yes
        INT_Handler   TMR2_INT,      _twentyMs,   ASM,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM
T0CON = %00000001
T1CON = %00000001
T2CON = %01011111
CCP1CON = %00000101
;@   INT_ENABLE  TMR1_INT     ; Enable Timer 1 Interrupts 
@   INT_ENABLE  TMR0_INT 
@   INT_ENABLE  CCP1_INT
@   INT_ENABLE  TMR2_INT

Main:
    NOP
    
GOTO Main

twentyMs:  ;really 10ms, but only acted on half the time
    toggle halftime_bit 
    if halftime_bit  = 1 then ;only perform this every other time this is called  
        timer0 = falltime/4   ;measured pulse length, send to 
        ;hserout [dec timer0,",",dec falltime,10,13]
        tmr0h = 255 - timer0.byte1
        tmr0l = 255 - timer0.byte0
        T0CON.7 = 1    ;start t0
        servo_out = 1     ;set servopin high        
    endif   
    @ INT_RETURN
    
PWMout:
    T0CON.7 = 0 
    servo_out = 0         ;at completion of timer set servo pin low
    @ NOP
    @ INT_RETURN

asm
PWMeasure

    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
ISR_2
    INT_RETURN

endasm

Walter

[Kenjones1935]

Scalerobotics,

The code you sent me has some incompatibilities with my system. I can fix some. Others....

You include DT_INTS-18.bas. I have DT_INTS-14.bas a la Derral Taylor. I changed the code.

You use "BAUDCON.3 = 1 ' Enable 16 bit baudrate generator". My compiler kicks that out. I do not know how to find out whether I have the equivalent. I do not even know how to start.

You use T0CON.7. My system has no such thing. Again I have no idea how to find out what is my equivalent.

Nuts! Ken