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kbruin79
Joined: 02 Aug 2010
Posts: 30
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| Hardware PWM "Pin RB3" |
 Posted: Tue Jan 17, 2012 11:45 am |
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Hello,
I am using CCS version 4.106 and I would like to set a PWM output at pin RB3 on PIC16F727. After I followed the instruction to setup the pwm on The PIC datasheet under section 15.3.8 then setup the APFCON register to steer the pwm to pin RB3 I wasn't able to see any pwm on that pin.
The same code worked for RC2 (PWM1)
Any help will be appreciated. Here is the code:
| Code: |
//---------------------------------------------------
//function prototypes:
//---------------------------------------------------
void make_portb_pins_digital(void);
void init_pwm2(void);
void pwm2(int16 a2d);
//---------------------------------------------------
// Main
//---------------------------------------------------
void main()
{
//MAKE RB3 DIGITAL OUTPUT
make_portb_pins_digital();
//INITIALISE PWM2
init_pwm2();
//SEND PWM ON RB3
pwm2(50);
while(1)
{
//DO NOTHING
}
}
void make_portb_pins_digital(void)
{
//GET THE BYTE ADDRESS OF PORTA AND B
#byte ANSELB = getenv("SFR:ANSELB")
#bit ANSELB_3=ANSELB.3
//make selected pins on port B digital
//------------------------------------
//MAKE PIN RB3 DIGITAL :PWM OUTPUT
ANSELB_3=0;
}
void init_pwm2(void)
{
//Assign pwm2 to RB3
//Disable the PWM pin (CCPx) output driver(s) by
//setting the associated TRIS bit(s).
TRISIOB_3=1;
//Load the PR2 register with the PWM period value.
PR2=40; // 3000hz
//Configure the CCP module for the PWM mode
//by loading the CCPxCON register with the
//appropriate values.
CCP2CON=0b00001100; // Set CCP2 PWM active high
//Load the CCPRxL register and the DCxBx bits of
//the CCPxCON register, with the PWM duty cycle
//value.
duty = 0; // set duty cycle to 0
CCP2CON_4 = duty_0; // Store duty to registers as
CCP2CON_5 = duty_1; // a 10-bit word
//store the eight MSbs in CCPR1L.
CCPR2L = duty >> 2; // store the remaining low byte
//clear the TMR21F interrupt flag bit of PIR1 register
PIR1_1=0;
//Configure the T2CKPS bits of the T2CON
//register with the Timer2 prescale value.
//and
//Enable Timer2 by setting the TMR2ON bit of
//the T2CON register.
T2CON=0b00000111;
//Wait until Timer2 overflows, TMR2IF bit of the
//PIR1 register is set.
wait_for_TMR2IF:
if (PIR1_1 == 0)
{
goto wait_for_TMR2IF;
}
//enable PWM by setting pin to output
TRISIOB_3=0;
//Assign pwm2 to RB3
APFCON_0=1;
}
void pwm2(int16 a2d)
{
duty=a2d;
CCP2CON_4 = duty_0; // Store duty to registers as
CCP2CON_5 = duty_1; // a 10-bit word
CCPR2L = duty >> 2; // store the remaining low byte}
}
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Last edited by kbruin79 on Tue Jan 17, 2012 12:15 pm; edited 2 times in total |
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temtronic
Joined: 01 Jul 2010
Posts: 9202
Location: Greensville,Ontario
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| Posted: Tue Jan 17, 2012 12:01 pm |
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Well you could make your life and anyone trying to read your program a LOT easier by using the CCS builtin functions !!
I got 'lost' about 1/3 down and gave up. Too much reading for such a simple program. |
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kbruin79
Joined: 02 Aug 2010
Posts: 30
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| Posted: Tue Jan 17, 2012 12:19 pm |
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| temtronic wrote: | Well you could make your life and anyone trying to read your program a LOT easier by using the CCS built-in functions !!
I got 'lost' about 1/3 down and gave up. Too much reading for such a simple program. |
I Simplified as much as possible, assume all constants, variables are defined. I will eventually use the built-in function but I would like to know why the code isn't working. |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Tue Jan 17, 2012 5:16 pm |
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you SAY you are using CCS but you are not-- it looks more like the structure of one of the crummy register oriented C's like HT or S-boost or Mikro...
for example, this mess for init of pwm2 mode and duty cycle :
//Assign pwm2 to RB3
APFCON_0=1;
COULD be WAY better handled by a #FUSE STATEMENT for the part in question --
----
then this approximate reduction
| Code: |
void init_pwm2(void) {
// do the proper setup_timer2(...); FIRST
set_pwm2_duty(0); // i do this BEFORE the setup enable
setup_ccp2(ccp_PWM);
// DONE
}
THEN THIS!!!
void pwm2(int16 a2d)
is really the same as the CCS function
set_pwm2_duty();
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this looks like falling back on assembler in HiTECH C - or one of the other really poor C for PIC compilers - this register defined - manipulation is NOT the CCS way at all, IHMO.
why not use the powerful C constructs CCS offers ??
perhaps you will get results if you READ the CCS manual
and try it their way next   |
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