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Pic16f818

uaefame said:
Wow amazing took me sometime to understand but I am willing to learn :)

Thanks eric

Here is the codes

Code: 
	[COLOR="Red"]banksel	PORTA
	banksel	TRISB[/COLOR]
	movlw	0		;set PORTB as all outputs
	movwf	TRISB
	banksel	PORTB

	movf	CCP1CON,W	;set CCP1 as PWM
	andlw	0xF0
	iorlw	0x0C
	movwf	CCP1CON

Again why Banksel PortA do u think its not needed?
Click to expand...

You're only showing part of the complete code, so it's out of context - but I would imagine that before it enters the code section you've shown it was set to bank 1, so the first instruction is to return to bank 0 (the place you normally want to be). In this particular case, the next line sets bank 1 again, so it's likely that BOTH lines could be left out if required.

It's also highly like that the different code segments were 'cut and pasted' together, which is probably why it occurred - but it does no harm.
 
I am doing fine, Thanks again for your concern blueroomelectronics. Thanks everyone for replying

movlw .126 ;set highest PWM value
banksel PR2 ;over this (127) is permanently on
movwf PR2
Click to expand...

Can someone explain these lines? Why .126 not .128??

I don't know why I became interested in PIC so suddenly. Maybe because of the mystery that it covers.
 
Last edited:
hi Hesham,

Do you have a copy of the 16F818 datasheet.?

Study the attached image.
Its important that you understand the Bank selection.

I would suggest 'learners' of assembly language, use the STATUS register bits RP1 amd RP0 for Bank selection.

Once they understand the Bank selection process then start using the Banksel directive.


EDIT:
Can someone explain these lines? Why .126 not .128??
Click to expand...

The 126 [7Eh], as explained in the program comments, at 127 [ 7Fh] 0111,1111 the motor is running forward, permanently ON.

For the value 7Fh is 0111,1111.
the next increment would be 128 [80h] 1000,0000, which in the comments is explained as a motor reversal.[ at the slowest speed].

255 [FFh] 1111,111 is top speed in reverse.

OK.?
 

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Last edited:
The 126 [7Eh], as explained in the program comments, at 127 [ 7Fh] 0111,1111 the motor is running forward, permanently ON.
Click to expand...

We set 126? why 127 is still motor running forward?

Another question what is the different between postscaler and prescaler?

Can someone show me a flow diagram how to set the period to (1/280hz) & duty cycle to 22%? any idea? using PIC16F818.



Thanks in advance
 
uaefame said:
We set 126? why 127 is still motor running forward?
Because with 126 there is a very short 'space' in the 'mark/space' in the PWM signal.
With 127 [7Fh, 01111111] there is no 'space' at all

Another question what is the different between postscaler and prescaler?
This is described in the datasheet, there is a block diagram showing how the
postscaler and prescaler are interconnected with the Timer.

Can someone show me a flow diagram how to set the period to (1/280hz) & duty cycle to 22%? any idea? using PIC16F818.
Please post the program you have written for this servo motor.

Thanks in advance
Click to expand...

Hi Hesham,
Most of the questions you are asking are explained in the PIC 16F818 datasheet, if you dont have one, goto Microchip Technology Inc. - a Leading Provider of Microcontroller and Analog Semiconductors and download a copy.
 
Last edited:
Let rephrase my question:

Anyone know a good tutorial about Pwm REALLY basic tutorial!!!!

I somehow get lost reading the manual! But I will try my best :)

I didn't know that everything is explained in the manual? Then why there is tutorial over the internet.

As mentioned, some times the manual get abit hard, therefore I am really interested in easy tutorial easy easy easy like one that eric keep explaining !!

Hehe If I recommend a writer! ErIC :)

yOU like explaining in a nice way :)

Thanks
 
Last edited:
Are you sure you want a PWM tutorial not a SERVO tutorial? PWM is similar but not the same as Servo.
PWM is for speed control on DC motors, lights etc...
Servo is a pulse no greater than 2ms at 20ms intervals.
I've used the hardware PWM channel for a servo but it's very course.
 
hi Hesham,
As Bill points out, you are looking for Servo information not PWM for motor control.

I will have a look thru my database, see if I can find anything useful.:)

I know I keep asking but have you built the 555 test rig,?
With an oscilloscope you could study the servo's characteristics.

It would be a useful tool if you plan to do lots of servo projects.
 
Here are the codes written for driving a servo motor.

Code: 
; 16F818 PWM example code  
; 
; Device 16F818  
	
	list	p=16F818	; list directive to define processor
	#include <p16F818.inc>	; processor specific variable definitions
	errorlevel -302, -207

	__config H'3F10'

	 
	cblock	0x20		;start of general purpose registers
	count			;used in delay routine
	count1			;used in delay routine
	counta			;used in delay routine
	countb			;used in delay routine
	temp			;temp storage
	;rate			;adc value
	endc



Fwd1	equ	0x00		;pin for left motor reverse
Rev1	equ	0x01		;pin for left motor forward

;pins 1 and 2 are the 1 PWM channel  

	org	0x0000
	nop			;for bootloader compatibility
	nop
	nop
	goto	START
	org	0x0010

START	call	Initialise

MainLoop: 
	
    movlw d'64'
	call Speed
    call Long_Delay

	movlw d'192'
	call Speed
    call Long_Delay

	movlw d'10'
	call Speed
    call Long_Delay

	movlw d'228'
	call Speed
    call Long_Delay

	goto MainLoop


Initialise: 

	banksel OSCCON
	movlw	b'01100000' ;uae1
	movwf	OSCCON 
	
	banksel	ADCON1		;turn off A2D
	movlw	0x0E; AN0 analog, rest digital, left justified [255]
	movwf	ADCON1

	banksel	PORTA
	banksel	TRISB
	movlw	0		;set PORTB as all outputs
	movwf	TRISB
	banksel	PORTB

	movf	CCP1CON,W	;set CCP1 as PWM
	andlw	0xF0
	iorlw	0x0C
	movwf	CCP1CON

	movlw	.126		;set highest PWM value
	banksel	PR2		;over this (127) is permanently on
	movwf	PR2
	banksel	TMR2

	movf	T2CON,W		;set prescaler to 4;;;16
	andlw	0xF8		;PWM at 2500HZ
	iorlw	0x01;;;2
	movwf	T2CON

	movf	T2CON,W		;set postscaler to 1
	andlw	0x07
	iorlw	0x00
	movwf	T2CON

	clrf	CCPR1L		;set PWM to zero

	bsf	T2CON,TMR2ON	;and start the timer running
	return

Speed:					;use value in W to set speed (0-127) 
	movwf	temp
	btfsc	temp,7		;if more than 128 set speed in reverse
	call	ReverseMtr	;so '1' is very slow forward
	btfss	temp,7		;and '129' is very slow reverse
	call	ForwardMtr
	andlw	0x7F
	movwf	CCPR1L
	return


ReverseMtr: 
	bsf	PORTB,Rev1	;set pins for reverse
	bcf	PORTB,Fwd1
	return

ForwardMtr: 
	bcf	PORTB,Rev1	;set pins for forward
	bsf	PORTB,Fwd1
	return


;Delay routines  

Long_Delay 
	return

	movlw	.50		;delay 5 seconds
	call	Delay100W
	return

Delay100W movwf	count		;delay W x 100mS
d2	call	Delay100	;maximum delay 25.5 seconds
	decfsz	count	,f
	goto	d2
	return

Delay255 movlw	0xff		;delay 255 mS
	goto	d0
Delay100 movlw	.100		;delay 100mS
	goto	d0
Delay50	movlw	.50		;delay 50mS
	goto	d0
Delay20	movlw	.20		;delay 20mS
	goto	d0
Delay10	movlw	.10		;delay 10mS
	goto	d0
Delay1	movlw	.1		;delay 1mS
	goto	d0
Delay5	movlw	0x05		;delay 5.000 ms (4 MHz clock)
d0	movwf	count1
d1	movlw	0xE7
	movwf	counta
	movlw	0x04
	movwf	countb
Delay_0	decfsz	counta, f
	goto	$+2
	decfsz	countb, f
	goto	Delay_0

	decfsz	count1	,f
	goto	d1
	return

;end of Delay routines  

	end
Btw, The servo motor didn't rotate?
I am actually still confuse how to set the period and the off and on time of the square wave.

Thanks in advance
 
Last edited:
You have almost no chance of building a line following 18 servo spider robot before the December deadline. My advice is to stop worrying about it and concentrate on learning C and PIC basics and enter the contest next year. You're in way over your head IMO.
 
uaefame said:
Here are the codes written for driving a servo motor.

Btw, The servo motor didn't rotate?
I am actually still confuse how to set the period and the off and on time of the square wave.
Click to expand...

That code is from my PWM tutorial, and doesn't feed a servo motor, it's for feeding two DC motors via H-bridges, so your servo isn't going to move (they don't 'rotate').

I agree with Bill, you don't have a prayer of meeting your deadline - you've been asking questions for ages, and still haven't even started.
 
uaefame said:
Here are the codes written for driving a servo motor.
Btw, The servo motor didn't rotate?
I am actually still confuse how to set the period and the off and on time of the square wave.

Thanks in advance
Click to expand...

hi Hesham,
That program is not for driving a servo.!

Also a servo motor does not 'rotate' [ limited to about 180deg]

Did you build the 555 servo tester.?

You must get a grasp of the Basics otherwise you will be posting for weeks and miss the deadline.

I would like to help, but you are not following our advice...:)

EDIT: I think there is an echo in here.:D
 
Last edited:
As I stated two weeks ago, clicky. I like helping people but Uaefame is either too stupid or too lazy to learn anything. When he starts asking questions that can't be answered in 30 seconds with a quick google I may be less critical.

Mike.
 
I took these codes from Pommie post the one he posted in page 2.

Code: 
;*******************************************************************
;                           16F877 PWM Program
;*******************************************************************

		include	"p16f877.inc"

		errorlevel	-302
		radix	dec

	__CONFIG _CP_OFF & _DEBUG_ON & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _HS_OSC & _WRT_OFF & _LVP_OFF & _CPD_OFF

		cblock	20h
OnTime:2
OffTime:2
		endc

		cblock	71h
int_work
int_status 
int_pclath
		endc

		org     0h
		nop
		goto    start
		nop
		nop

interupt	movwf	int_work
		swapf	STATUS,W
		movwf	int_status
		bcf	STATUS,RP0
		bcf	STATUS,RP1
		movfw	PCLATH
		movwf	int_pclath
		clrf	PCLATH

		btfsc	PORTB,0
		goto	TurnOff
; turn on the output and write the on time
		nop;		delay to make both path identical
		bsf	PORTB,0;<<<<<<<<<< Break Point
		movfw	OnTime+1
		movwf	CCPR1H
		movfw	OnTime
		movwf	CCPR1L
		goto	DonePWM

TurnOff		bcf	PORTB,0;<<<<<<<<<< Break Point
		movfw	OffTime+1
		movwf	CCPR1H
		movfw	OffTime
		movwf	CCPR1L
DonePWM
		bcf	PIR1,CCP1IF;	reset special event trigger interupt

		movfw	int_pclath
		movwf	PCLATH
		swapf	int_status,W
		movwf	STATUS
		swapf	int_work,F;	swap to file
		swapf	int_work,W;	swap to work
		retfie


start		bsf	STATUS,RP0
		bcf	STATUS,RP1
		bsf	STATUS,IRP;	all indirest access is to 100h - 1ffh
		 movlw	(0<<NOT_RBPU|0<<INTEDG|0<<T0CS|0<<T0SE|0<<PSA|B'000'<<PS0)
		movwf	OPTION_REG
		movlw	b'11111110'
		movwf	TRISB
		bcf	STATUS,RP0
		movlw	(b'01'<<T1CKPS0|0<<T1OSCEN|0<<NOT_T1SYNC|0<<TMR1CS|1<<TMR1ON)
		movwf	T1CON;		enable timer 1
		movlw	low(45000)
		movwf	CCPR1L
		movwf	OnTime
		movlw	high(45000)
		movwf	CCPR1H
		movwf	OnTime+1
		movlw	low(5000)
		movwf	OffTime
		movlw	high(5000)
		movwf	OffTime+1
		movlw	(0<<CCP1X|0<<CCP1Y|b'1011'<<CCP1M0);	enable special event trigger on CCP1
		movwf	CCP1CON;	
		bsf	STATUS,RP0
		bsf	PIE1,CCP1IE;	enable CCP1 interupt
		bcf	STATUS,RP0

		movlw	(1<<GIE|1<<PEIE|0<<T0IE|0<<INTE|0<<RBIE|0<<T0IF|0<<INTF|0<<RBIF)
		movwf	INTCON;		enable Peripheral interupts

Loop		
		goto	Loop


		END

The codes is written for p16F876A
I changed the include file "p16F877.inc" and the title to 16F877 when I run this it give me error still.

What you think is wrong? BTW these code is written for PIC16F876A and it appear that the manual of both of them is same. Therefore, I assume the codes must be similar.

My interested is to assemble these codes in my PIC16F877 if you have any idea what wrong while changing the codes from 16F876A till PIc 16F877 please tell me.

Thanks again for the ace forum :)
 
The 877 is virtually the same as the 877A
The CMCON is not there so just ignore it
It uses a different programming algorithm (not applicable)

What error are you getting?
 
Error[113] C:\MPLAB\16F877 SERVO MOTOR\SENSOR.ASM 10 : Symbol not previously defined (_WRT_OFF)
Click to expand...

This one? Strange do you think i need to remove it?
 
When I am so close to experiement something out, something goes wrong.

Strange how the odds work against you.

The PIC16F877 is so big that it doesn't easily fit or can't even fit to the breadboard.

Any ideas? Do you think i need another way to do it?
 
Last edited:
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