PBP projects for R/C models

[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

[Kenjones1935]

I searched all the .inc files in the microchip/MPASM suite directory for the string BAUDCON. I got many hits. None were from the PIC16F8xx set of microprocessors.
The hits mostly said "BAUDCON EQU h'019f'" in BANK 3.

There are no such entrees in the PIC16F8xx .inc files.

How do I find out what BAUDCON means in its context so that I can translate to my PICkit 2 context?

[Archangel]

There are no such entrees in the PIC16F8xx .inc files.

How do I find out what BAUDCON means in its context so that I can translate to my PICkit 2 context?

Hi Ken,
He is using an 18F part, look in the data sheet for the chip he is using.
For your code just comment that line out and try it. I think I would try different settings in the defines which control the Baud Rate of the hardware serial port as he set up for 19200, but you could use that.
Ok, 18F4520 has EUSART which uses BAUDCON and reconfigures pin as both input/output on the fly . . .
You got snow, we got rain . . .

[ScaleRobotics]

Hey Ken, you can either take the serial out, or change it a bit. Here is one to use a slower baudrate, without using the baudcon.3 setting.

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 64 ' 19200 Baud @ 20MHz, 0.16%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically

I use a program from Mister E, called Mister E PIC Multi-Calc that spits all these above settings out after you pic a baud rate. Pretty cool! http://www.picbasic.co.uk/forum/show...9&postcount=38

Sometimes PIC chips can be a pain because the newer chips will move things around on us. So when we try to learn a different chip, or upgrade to a different part, things do not work without a bit of leg work.

I was using a PIC18F2520, which had a register called T0CON for adjusting the Timer0 or TMR0. That sounds like it makes sense. However, on the PIC16F887 that you are using, the same Timer0 TMR0 is adjusted by using .... the Option Register. Not quite making as much sense, is it.

Anyway.... HOW do I know this? Answer: I do not. I have to look up both data sheets for each of those pic chips, and compare them. Not all 375 pages, but just whatever portions I think are giving me trouble. In this case, the Timer0. Then I have to see that everything that is set in the PIC18F2520 for the timer, is set for the PIC16F887. Then I will probably have to do the same thing for the other timers. AND, it will probably not work when I first try it, because I will probably miss something.

So, looking at page 77 of your data sheet, and page 125 of my data sheet, lets see what we can screw up, I mean "test".

Well I had it set to:

TMR0ON - off
T08Bit - configured as a 16 bit timer (this could be a problem)
T0CS - Internal instruction cycle clock
T0SE - increment on low to high transition of clock pin
PSA - use prescaler selection bits
T0PS - 1:4 prescaler selection bits

Now lets see what we have for the Option register...
Well, looking at the data sheet, your chip's T0 is only 8 bit, but if we are lucky, we will just have lower resolution. Timer0 is the time base for creating a servo pulse out from 1 to 2 ms.

Option_Reg
RBPU - Port B pull ups (nothing to do with timer) probably leave off - 1
INTEDG - Nothing to do with timer
T0CS - keep at 0 like above
T0SE - keep at 0 like above
PSA - keep at 0 like above
PS - we can start at 001 like above, but we might have to change things up since this
is not a 16 bit timer.....If I was smarter about how these worked, I could mathematically figure this out.....

Now, how do we start this timer0, because it looks like bit 7 is NOT going to do this for us...

To be continued .....

[boroko]

Scalerobotics,

Bravo! very well laid out explanation (well at least part one). That is the kind of stuff that drives newbees nuts and makes them give up in frustration. There is no easy place to learn it if you don't have a mentor. Patient, concise, and relevant. Nice job.

Bo

[Kenjones1935]

I awoke this morning looking out my window onto eight new inches of wind packed snow. Plenty of time to think.

What scalerobotics said makes sense to me. In 1957 I was programming the AN/FSQ-7 SAGE Air Defense computer. We worked in machine language. It took us years to develop and distribute a symbol and subroutine library sufficient to allow us to focus on the radar data reading, intercept calculating algorithms needed to accomplish air defense. Building this subroutine library was a big task. The architecture of the machine did not change.

This morning I said to myself, "Back to basics." It may have been a mistake for me to purchase PICbasic PRO. Without being able to tap into the developments of others on the 16F88x structure, I may be better off in ASM. That way I will be forced back to basics.

This world of microprocessors reopens the academic importance of old fashioned "computer science". I was afraid that we had become too product oriented to care what is a "register".

I have two PIC books:
PIC PROJECTS by Parchizadeh and Vuksanovic
and
RUNNING SMALL MOTORS WITH PIC MICROCONTROLLERS by Sandhu

Seems like I should cease dreaming of getting a prototype to blink in sync with a PWM input signal and get back to the books. I've got plenty of time. Did I mention that we are snowed in without an all wheel drive car?

Ken