PBP projects for R/C models

[malc-c]

Hi,

Following on from a suggestion on the main PBP forum, it is hoped to get people to post up code snippets for anything RC model related. I'll start the ball rolling by posting code that makes an LED pulse like a beacon and is controllable from a transmitter. - This was a result of my own bit of code and suggestions from guys on this forum on how to use pulsein command to detect the signal from the receiver.

'****************************************************************
'*  Name    : RC Input - 12F675                                 *
'*  Author  :                                                   *
'*  Notice  : Copyright (c) 2009                                *
'*          : All Rights Reserved                               *
'*  Date    : 27/10/2009                                        *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*          :                                                   *
'****************************************************************

' set up PIC config

@ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON

 __CONFIG
 _INTRC_OSC_NOCLKOUT
 _WDT_ON
 _PWRTE_ON
 _MCLRE_OFF
 _BODEN_ON

OPTION_REG = %10000000                      ' Pull-ups = off, GPIO.2 = I/O, prescaler to Timer1
GPIO = %00000000                            ' All outputs = 0 on boot
TRISIO = %00001000                          ' GPIO.3 input, GPIO.0,2,3,4,5 output
ANSEL = 0	                                ' Set all digital
WPU = 0                                     ' Internal pull-ups = off
ADCON0 = 0                                  ' A/D off

;set varibles

signal VAR GPIO.3                           'GPIO.3 is used to the receiver
pulse  VAR BYTE                             'pulse is used to store the result
led var GPIO.0                              'GPIO.0 is the output we want to flash
i var byte                                  'i is used for the for next loop to generate width of pulses
getout var bit                              'used to check switch routines

'-------------------------------------------------------------------------------

main:
PulsIn signal, 1, pulse                     ' reads signal from receiver
IF (pulse >= 100) AND (pulse <= 160) Then   ' threshold for activation
Low GPIO.0                                  ' turns LED off
Else
goto flash                                  'if pulse is ouside range goto flash
EndIF
GoTo main                                   ' do it all again

flash:
for i = 1 to 254                            ' for next loop                                             
Pwm GPIO.0,i,1                              ' send pulse to GPIO.0 for lenght i increasing brightness
pause 1
if i=253 then                               ' test to see value of i
i=1                                         ' if test is true then set 1 to 1 and getout to 1
GetOut=1 
if Getout=1 then goto down                  ' if getout is q then jump to down routine
endif
next i

down:                                       ' same as flash but decreases brightness
for i = 254 to 1 step -1                                              
Pwm GPIO.0,i,1
pause 1
if i=2 then                                 ' test of value i, if i =1  then
i=1                                         ' set i to 1 and getout to 0
GetOut=0  
if Getout=0 then goto main                  ' test value of getout - if 0 go to start of program
endif
next i

[Kenjones1935]

Please, if you are interested, take a look at the
"How do I give a radio control car autonomous control"
Thread. I have a PICkit 2 and PICbasic programming package.

Attached is a sketch of what i need to do. I think. Any suggestions would be greatly appreciated. The forum does not let me attach the same file twice.

http://www.picbasic.co.uk/forum/atta...1&d=1263008711


Ken Jones

[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

[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?

[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

[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]

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".
Ken

Ken, I hope I did not discourage, for it was my intent to encourage. But back to basics is always a good idea, no matter what path you choose. For PIC devices, it can be a difficult task to transfer a program from one type of device to another.

A better place to start on the learning curve, might be to use Darrel Taylors interrupt code examples, and try to get the interrupt blinking led going on your device. Then try to modify it in some way that is closer to the end product you want. In that way, it forces you to learn about different registers, but only a few at a time. Here is Darrels blinky example. http://darreltaylor.com/DT_INTS-14/blinky.html

Joe had some great advice. In trouble shooting, it is always helpful to figure out what parts of the code DO work. I always like using the serial port to help tell me what is happening in the device, and to check register values, etc.

Let us know how we can help you.

Walter

[Kenjones1935]

I got Darrel Taylor's blinky to work on my PICkit 2 16F887. I had to change the output pin to the LED to match the printed circuit on the 44 pin demo board.

Now I would like to get blinky to interrupt on the rising edge and the falling edge of a signal coming in CCP1 which is RC2.

Darrel Taylor's blinky contains this line

@ INT_ENABLE TMR1_INT ; enable Timer 1 interrupts

Where do I look for the definition of INT_ENABLE? I used SEARCH. I had no luck at all.

Ken

[ScaleRobotics]

That's a great start Ken!

INT_ENABLE is a Darrel Taylor command for his DT_INTS. This is the same as enabling, or disabling a certain interrupt. To set up CCP interrupts, you first add a line like my code had:

INT_Handler   CCP1_INT,      PWMeasure,   ASM,  yes

Then enable it:
@ INT_ENABLE CCP1_INT

But you will also have to configure it. Make portc.2 an input. And configure your CCP1
CCP1CON = %00000101 ;capture every rising edge

Now I used Chuck's code to do the capture. It needs the sub16.inc include file to be included, and we will need some variables like

risetime var word      ;used for pulse width measure start of pw
falltime var word      ;time at end of pulse width
falltime_l var falltime.byte0
falltime_h var falltime.byte1
risetime_l var risetime.byte0
risetime_h var risetime.byte1

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

Now, if you read the data sheet, you see in 11.1 Table 11-1 that capture mode uses timer1. So you will have to set this. Looks like it may be same settings as I have in T1CON. This will also start the timer. It runs continuously, and we don't care about interrupts on T1. We just want to read the timer at interrupt high edge of CCP1, and read timer on low edge of pulse. Then we should have a value present at falltime, representing the length of the pulse.

[Kenjones1935]

I did not expect this project to be so discombobulating.

Thanks to this forum's help, I think I will get it.

ken

[ScaleRobotics]

Yes, you have picked a very challenging project.

The servo part broken down into basic steps of what is going on here. (Other interrupt sources, and different timers could be substituted, but this is what I am using).
__________________________________________________ _________________________________________________
Pulse Sensing:
Using CCP interrupt and calculate (pulse_width = falltime - risetime) with CCP capture low byte CCPR1L and capture high byte CCPR1H (these use Timer1). To do this, bits must be changed from capture on rise, to capture on fall.

Pulse Width Generation:
Need to create interrupt from about 1ms to 2ms in length. To do this, we load a timer with pulse width value, bring servo pin high, start timer, when interrupt occurs, bring servo pin low. I used Timer0.

Pulse Period Generation:
Need to generate 20ms time frame for sending servo signals. I used Timer2. Servo out pins need to pulse every 20 ms.
__________________________________________________ _________________________________________________

On a side note:
Now just to discombobulate things a little bit (more!), cheating can sometimes work. Problem is, that you want to run one of your outputs through a motor controller, and these don't like cheaters. They like very reliable 20ms time (Pulse Period) frames for the servo pulses. So, where you might have gotten away with using PBP's pulsin and pulsout commands for sensing and controlling servo's, you will not get away with using the pulsout command for controlling your motor controller.

One place you could get away with a little cheating, is to use Pulsin command to sense your receiver's servo pulses. Then you would not have to worry about the servo Pulse Width sensing. I have used this with an RC autopilot project, and it was smooth enough to fly. But, since you are doing all this work learning about interrupts, and timers, you might as well do it the right way, and measure the pulse with an interrupt.

[Kenjones1935]

Scalerobotics.

I have not been successful getting the RC knowledgeable folks to come clean with the exact signal pulse width specs. The hobby RC folks at our local RC Excitement racetracks and store

http://www.rcexcitement.com/

say that neutral (braking) is 130ms. This makes sense if the max pulse size is 256ms (2 to the 8th for convenient digital counting). How often that pulse is expected I am not sure. I think I read that the shortest pulse is about 50ms and the longest about 200ms. But I have no idea where or how I got that impression.

It would be nice if I could implement a program on my PICkit such that my eyes could detect this variation by observing the glow of an LED.

I neither own an oscilloscope nor have easy access to one. I do have some contacts at the Fitchburg State College Computer Science Department. I could call them and take over my car for a definitive answer.

Enough talk. I'm supposed to be thinking and tinkering.
Ken

[ScaleRobotics]

Most of the RC stuff out there uses something like this, but there are exceptions:

And it is done 50 times per second, or every 20ms.

The hobby RC folks at our local RC Excitement racetracks and store say that neutral (braking) is 130ms.

I think the guys at your RC Excitement might be off by a decimal point or two if they are telling you neutral is 130ms.


If that was neutral, it would take about 1 second to make any corrections to steering or throttle. In my mind that is a little slower than you need for a fast car like the one I saw in your other thread.

Most RC receivers send out a pulse, one at a time, to each servo. So with the longest (2ms) pulse, an eight channel receiver can still fit all 8 x 2ms pulses in the 20ms bandwidth given by the cyclic 50 times per second update rate.

[Kenjones1935]

These RC Excitement guys just said 150 and 125 and 175. They never said the units. I just surmised milliseconds.

Last week you sent me two short programs. You also suggested that I go to Darrel Taylor's page and grab some code. I got his "blinky" to compile and work with the minor adjustments of changing the output to an LED register and the DT_INT-14.bas fix. I never got either of yours to compile and run.

On page 125 of your 18F2520 spec I found T0CON containing TMR0ON, T08BIT, T0CS, T0SE, PSA, T0PS2 AND T0PS1. I could not relate any of this to the contents of pages near 77 of my 16F887 spec. I also could not find in any code you posted where you set these bits.

Scalerobotics thought I might be able to measure the PWM radio receiver outputs if I converted it to a serial stream. Good idea, but I don't know what to do with a serial signal.

I would feel successful if I could see on a flashing LED that my radio receiver is working and that the PIC can read it. (I know it is working because the car wheels turn.) This is the intent of the first code (RC-Input - 12F675) Scalerobotics sent me. It originate with Malcolm from Hertfordshire, UK.

I'd like to get that working.

Time out. Gotta check the TV for results of the Massachusetts special US Senatorial election.

Ken

[Kenjones1935]

You guys keep suggesting the serial signal. Could it be that you have a method of debugging/trouble shooting your microprocessor code on line?

I just looked up USB on wikipedia. It is a "Universal Serial Buss" OH! I did not know that. So NOW I look at the "view" pull down menu on my MicroCode Studio GUI and discover "Serial Communicator" and "Easy HID USB Wizard".

There is clearly a lot for me to learn in C:\PBP\USB. Is that where I should start? I just opened MPLAB IDE for which I could see no purpose. I am beginning to understand but I am not sure where to start.

Ken

[ScaleRobotics]

Last week you sent me two short programs. You also suggested that I go to Darrel Taylor's page and grab some code. I got his "blinky" to compile and work with the minor adjustments of changing the output to an LED register and the DT_INT-14.bas fix. I never got either of yours to compile and run.

Mine will only compile properly for a PIC18F device, for sure with a PIC18F2520. It will need some work to translate for PIC16F devices.

On page 125 of your 18F2520 spec I found T0CON containing TMR0ON, T08BIT, T0CS, T0SE, PSA, T0PS2 AND T0PS1. I could not relate any of this to the contents of pages near 77 of my 16F887 spec. I also could not find in any code you posted where you set these bits.

Sorry, it is page 75 in the datasheet, and page 77 on Acrobat. Look for the page that has:
REGISTER 5-1: OPTION_REG: OPTION REGISTER on it. Where I set these registers is here:

T0CON = %00000001
T1CON = %00000001
T2CON = %01011111
CCP1CON = %00000101

Scalerobotics thought I might be able to measure the PWM radio receiver outputs if I converted it to a serial stream. Good idea, but I don't know what to do with a serial signal.

You mean you don't have any computers laying around with a serial port? Yeah, I guess it is like that in my house too! Your PicKit2 comes with a great resource (in my opinion). It has a serial port built in, and you can use it to see what your program is doing. Or in this case, figure out what your Pulse Width Measurement is doing. With the Pickit2 software, go to tools, then choose the Uart tool. Make sure you are sending your serial data to the right pin. In this case, you will have to use the serout commands, as the pickit pins will not be connected the the hardware serial port. Follow the serout as defined in the PBP manual.

I would feel successful if I could see on a flashing LED that my radio receiver is working and that the PIC can read it. (I know it is working because the car wheels turn.) This is the intent of the first code (RC-Input - 12F675) Scalerobotics sent me. It originate with Malcolm from Hertfordshire, UK.

LED's can be a good trouble shooting tool. However, we do not even know if the timebase is going to be similar in your chip, or what crystal you are running, etc. The serial port will be able to tell you so much more about what is going on. I think you will feel even more satisfied seeing actual results.

I'd like to get that working.

Me too!

One thing I learned about was MicroCode Studio's ICD (in circuit debugger). It is a great tool to see what your code is doing. It lets you step through, or view it, while allowing you to view registers, etc. I used it a lot in the beginning, then I started a few projects that were very time dependent, so I could not use the ICD in them, so I have not used it in a long time.

And about that USB HID ... what about the back to basics part?

-Walter

[mackrackit]

Ken,

Get a USB to serial converter. You do not want to mess with USB from the PIC at this time. Keep it simple.

The use the serial terminal in MCS.

[Kenjones1935]

I have discovered the Analyzer Tool in the PICkit Tool Logic Tool package.

It looks like this tool will provide me a picture of the output of my radio receiver if I can get Scalerobotics' program to work. I have both MPLAB IDE and PICbasic PRO packages. They have some duplications. I have a book "PIC PROJECTS" which pontificates the advantages of MPLAB. I have an impressive PICkit Tool HELP menu.

My impression is that the PICkit package is what I should focus upon. Does that make sense?

Ken

[Kenjones1935]

I succeeded in getting scalerobotics second code sample to compile.

This is the one that samples PWM incoming and puts it out the serial port. It created an .asm file that would not build. The list of errors is too large to publish here. (Besides that it does not word wrap well.)

I am completely missing something. I do not understand PICBASIC PRO.The multiple hundred page microchip DATA SHEETS blow my mind. I try to read a section (16F887 Page 74 on SOFTWARE PROGRAMMABLE PRESCALER) and I can not put it in context.

I am not sure where the basics are that I am meant to go back to. I have a couple of paperback books. Maybe I should read page by page.

Ken

[rmteo]

A good understanding of PIC's as well as a some idea of how BASIC works will be a great help to your success in getting this project going. Here are 2 free books that will give you a good start.

PIC Microcontrollers
Programming PIC MCUs in BASIC

[Kenjones1935]

Scalerobotics,

How did you know of the contents of:

http://darreltaylor.com/DT_INTS-14/asm_ints.html

and

http://www.picbasic.co.uk/forum/show...39postcount=38

Is there a centralized resource?

Ken

[Acetronics2]

Hi, Rmteo

If your first reference is useful to understand the Pics themselves, the second is TOTALLY unadapted to help a PbP Beginner for Basic, as the two " basics" are much, much, much differents one from the other ...

let's say ... Pbp looks like the old GWBasic - or very close to Parallax Basic ... But Mikroelektronika Basic ( did I say " Basiç " ??? ) looks very, very, very close to " C " ...

Do not tell me " false " ... as I use those 3 Compilers !!!

Sooooo, the best Basic course for PbP you can find is PARALLAX ... here:

http://www.parallax.com/tabid/535/Default.aspx

here ... you'll find a progressive and comprehensive learning curve, with level adapted examples, and OVERALL ...
What you've learnt is directly re-usable ...

last, but not least !

Alain

[Kenjones1935]

The computer architecture part of

http://www.mikroe.com/en/books/picmcubook/ch0/

reminded me of the lectures I received in 1957 when I was hired as a computer programmer by Lincoln Labs to work on the SAGE Air Defense computer. If you want to read what preceeded the picmcubook (above) look at:

http://history.sandiego.edu/GEN/20th/sage.html

I started my career coding for SAGE. I graduated from CISCO Systems as a Senior Software Engineer in 2003. Since that time my mind has not been focused on technology.

I feel that my problem with PBP and the 16F887 is lack of access to the 'common knowledge'. How did scalerobotics know about darreltaylor?

[mackrackit]

How did scalerobotics know about darreltaylor?

Darrel is one of the moderators of this forum and one of the largest contributors.
Hands down he is the one with all of the "interesting" stuff.

Hang around and you will meet him.

Ken,
You are doing fine for starting work on a new system. We talk about "basics". Just work on things one piece at a time, not the whole project. When all of the pieces work then put it all together.

I get a laugh from the "Object Oriented" folks from other languages. And I even hear about "extreme programming".

Us working with MCUs have been doing the above sort of thing for.... ever.
Write your code in pieces, make sure each piece works, then combine the pieces.

So in your case, reading the PWM is one part, get that working.
Move on to running a motor with PWM, a separate little project and code.
Work on the sensors, another separate project.
And so on...

Pretty soon you will have the whole thing finished and understand it all.

Architecture... Princeton or Harvard?

[rmteo]

You can get a lot of "common knowledge" here Microchip Technology User Forums as well as quite a few other places.

[Bruce]

Just curious .. rmteo ... do you use PBP?

[Kenjones1935]

The PICBASIC PRO compiler book that comes (for $250) with MIcroEngineering Labs product does not mention built in routines. I found a chapter in a MikroElektrnonika "Programming PIC MCUs in BASIC"on line book devoted to these. I assume they work with my system. True? I don't think so.....sigh

http://www.mikroe.com/en/books/picbasicbook/05.htm


The above book says,

-------start snip---------------
Prototype sub procedure EEprom_Write(dim Address as byte, dim Data as byte)
Description

Function writes byte to [Address]. [Address] is of byte type, which means it can address only 256 locations. For PIC18 MCU models with more EEPROM data locations, it is programmer's responsibility to set SFR EEADRH register appropriately.

All interrupts will be disabled during execution of EEPROM_Write routine (GIE bit of INTCON register will be cleared). Routine will set this bit on exit

Ensure minimum 20ms delay between successive use of routines EEPROM_Write and EEPROM_Read. Although EEPROM will write the correct value, EEPROM_Read might return undefined result.
Example

for i = 0 to 20
EEPROM_Write(i, i + 6)
next i
-------------------end snip----------------

I tried the following bit in my PBP compiler.

i VAR BYTE
for i = 0 to 20
EEPROM_Write (i, i + 6)
next i

It complained that the EEPROM line has a syntax error.

What am I just not grasping.....??? I assume the two BASIC packages differ. The question is where do I find the built in routines that come with MY PBP?

Ken

[Bruce]

Ken,

If you're working with PBP, you need to forget about anything you read for the Mikroe BASIC compiler. These are two totally different compilers.

Everything you need to know about PBP is in the PBP manual. What you don't understand, just ask about here.

[mackrackit]

Ken,

Have you been to this page?
http://www.melabs.com/resources/samples.htm

As for routines. I would say that just about every "command" listed in the PBP manual is a routine. ADCIN for example. The routine for reading the chip's ADC is built into that command.

Keep asking questions

[Kenjones1935]

This PWM exercise is designed just for what I have done.

http://www.melabs.com/resources/samples/pbp/hardpwm.bas

After loading the .hex into the RC car (carrying my PICkit2), hooking up another battery and connecting CCP1 to the electronic speed control, The wheels spin!!

Ain't technology grande!

Ken

[mackrackit]

COOL!!!
Another piece down!

Did you get Walter's PWM reading code to work?
If so then maybe now you can combine the two.

If incoming PWM is X then wheels turn sort of thing?