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jjacob
Joined: 08 Mar 2008
Posts: 54
Location: PORTUGAL (PORTO)
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| PWM, Timer0, Timer2 in 12F615 |
 Posted: Sat Jul 18, 2009 9:59 am |
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Hello.
I'm using :
Compiler Version : 4.057
PIC12F615
5V power supply
Internal Oscillator ...
I need to count the frequency of the input signal... 0 ... 50Hz ... and make it in a 0 ... 5V signal.
I've tested this software in 18F452 and it worked ... but it's a big PIC ... so I want to put this working in a 12F615...
This the code :
| Code: |
#include <12F615.H>
#fuses INTRC_IO,NOWDT,NOPROTECT,NOMCLR,NOBROWNOUT
#use delay(clock=4000000)
#define in PIN_A3
int sec, N1;
int16 pwm, count;
//http://www.ccsinfo.com/forum/viewtopic.php?p=118216
#int_RTCC
void RTCC_isr(void) {
sec++;
if(sec>=2){
// Instead of calculate pwm to 1023, i limit to 1000... for easier math...
// Max. freq. is 50Hz
// 0Hz - 0V. For 50Hz - 5V.
// pwm=(N*1000)/50, where N is the frequency value...
// As i sample every 2 seconds, freq=count/2;
pwm=((((count)/(int16)2)*(int16)1000)/((int16)50));
count=0;
sec=0;
N1=1;
}
}
// I do software 'debouncing', because the input of the pic, comes from a
// LM311 and sometimes is has some 'garbage' ... so i complete with software...
void wait_for_low() {
int count=0;
while(count<100 && !N1){ /* debouncing... */
if(!input(in)) count++;
delay_us(100);
}
}
void wait_for_high() {
int count=0;
while(count<100 && !N1){ /* debouncing... */
if(input(in)) count++;
delay_us(100);
}
}
// ************************************
// RTCC is the same as TIMER0 !!!!!
// ************************************
void main(){
setup_adc_ports(ADC_OFF);
delay_us(10); // A small delay is necessary
setup_timer_2(T2_DIV_BY_4, 255, 1);
setup_ccp1(CCP_PWM); // Configure CCP1 as a PWM
// I get an interrupt each 2 seconds ...
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_16);
enable_interrupts(INT_RTCC);
enable_interrupts(GLOBAL);
count=0;
sec=0;
N1=0;
set_pwm1_duty(512);
while(1){
wait_for_low();
wait_for_high();
count++;
if (N1){
set_pwm1_duty(pwm);
//printf("\n\r count = %Lu pwm = %Lu", count, pwm);
N1=0;
}
}
}
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For test the 12F615, I made a simple software : ReadADC put in PWM.
It worked fine, if I varied the input voltage in the ADC the PWM changed in the same way.
With the above code, I made some debug, commenting lines and I always had the same PWM (50%) because of the line before the 'while(1)' in the end of my code.
When I uncomment the line :
| Code: | | enable_interrupts(GLOBAL); |
The PWM goes to zero and nothing change on the PWM output, even with a 50Hz input !!!
Any idea ?? PWM works with Timer2 ... my interrupts are with Timer0 ... any problem with this ? I'm using the internal oscillator. Is this a problem ?
Thank you for your attention
Jacob |
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jjacob
Joined: 08 Mar 2008
Posts: 54
Location: PORTUGAL (PORTO)
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| Posted: Sat Jul 18, 2009 12:35 pm |
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Hi all 
I found the problem ...
Timer0 in 18F452 is a 8/16 bit (i was using as a 16bits...).
Timer0 in 12F615 is a 8 bit !! So the migration was not direct !!!
I change the code and use timer1 to do the 2 seconds 'tick'... I think that the calculations are correct. I have an interrupt ... near every 2 seconds ...
To see that i use a 'led' 
Still, i haven't understand why i have to put 'sec>=8' instead of 'sec>=4' for the 2 seconds pwm refresh value ??!!!
Here is the code :
| Code: |
#include <12F615.H>
#fuses INTRC_IO,NOWDT,NOPROTECT,NOMCLR,NOBROWNOUT
#use delay(clock=4000000)
#define in PIN_A3
#define led PIN_A4
int sec, N1;
int16 pwm, count;
//http://www.ccsinfo.com/forum/viewtopic.php?p=118216
// Timer1 interrupt is called every 0.524288 segundos
// 'timer1' é de 4MHz/4 = 1MHz = 1us
// 1us*2^16*8 = 0.524288 seconds ???????? why 'sec>=8'
// With this math, it would be 'sec>=4' ???????
#int_timer1
void timer1_isr(void) {
sec++;
if(sec>=8){
// Instead of calculate pwm to 1023, i limit to 1000... for easier math...
// Max. freq. is 50Hz
// 0Hz - 0V. For 50Hz - 5V.
// pwm=(N*1000)/50, where N is the frequency value...
// As i sample every 2 seconds, freq=count/2;
pwm=((((count)/(int16)2)*(int16)1000)/((int16)50));
output_toggle(led);
//printf("count : %Lu pwm = %Lu\n\r", count, pwm);
count=0;
sec=0;
N1=1;
}
}
// I do software 'debouncing', because the input of the pic, comes from a
// LM311 and sometimes is has some 'garbage' ... so i complete with software...
void wait_for_low() {
int count=0;
while(count<100 && !N1){ /* debouncing... */
if(!input(in)) count++;
delay_us(100);
}
}
void wait_for_high() {
int count=0;
while(count<100 && !N1){ /* debouncing... */
if(input(in)) count++;
delay_us(100);
}
}
// ************************************
// RTCC is the same as TIMER0 !!!!!
// ************************************
void main(){
setup_adc_ports(ADC_OFF);
delay_us(10); // A small delay is necessary
setup_timer_2(T2_DIV_BY_4, 255, 1);
setup_ccp1(CCP_PWM); // Configure CCP1 as a PWM
setup_timer_1(T1_INTERNAL|T1_DIV_BY_8);
enable_interrupts(INT_TIMER1);
enable_interrupts(GLOBAL);
count=0;
sec=0;
N1=0;
set_pwm1_duty(512);
output_low(led);
while(1){
wait_for_low();
wait_for_high();
count++;
if (N1){
set_pwm1_duty(pwm);
//printf("\n\r count = %Lu pwm = %Lu", count, pwm);
N1=0;
}
}
}
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Now i have a PWM refresh rate of about 2 seconds ...
But i would like to do the EXACT math ... i've looked into 12F615 datasheet 'TIMER1 BLOCK DIAGRAM' but cant' figure out if the clock source is FOsc or FOsc/4. For my code i would say that is FOsc ... but i can't understand ...
Can anyone help me ??
Thank you
Jacob |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Jul 18, 2009 3:21 pm |
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| Quote: |
setup_timer_1(T1_INTERNAL | T1_DIV_BY_8);
but can't figure out if the clock source is FOsc or FOsc/4.
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The PIC data sheet says this:
| Quote: |
REGISTER 6-1: T1CON: TIMER1 CONTROL REGISTER
bit 1 TMR1CS: Timer1 Clock Source Select bit
1 = External clock from pin RC0/T1OSO/T1CKI (on the rising edge)
0 = Internal clock (FOSC/4) |
You have configured the Timer for T1_INTERNAL, therefore the clock
is Fosc/4. |
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jjacob
Joined: 08 Mar 2008
Posts: 54
Location: PORTUGAL (PORTO)
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| Posted: Sat Jul 18, 2009 4:24 pm |
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Thank you PCM programmer for your simple explanation 
In the datasheet that i've download it is writen :
bit 1 TMR1CS: Timer1 Clock Source Select bit
1 = External clock from T1CKI pin (on the rising edge)
0 = Internal clock (FOSC/4) or system clock (FOSC)(3)
(3) is a note :
3: See T1ACS bit in CMCON1 register.
In CMCON1 :
bit 4 T1ACS: Timer1 Alternate Clock Select bit
1 = Timer 1 Clock Source is System Clock (FOSC)
0 = Timer 1 Clock Source is Instruction Clock (FOSC\4)
CCS is a 'high level' language, how can i know what is the state of bit 4 in T1ACS ?
Thank you for your attention
Jacob |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Jul 18, 2009 4:32 pm |
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I'm not at my regular computer so I didn't have access to the 12F615
data sheet. I used the 16F877 data sheet.
To see what the compiler is loading into the Timer1 registers:
Go to the Project / Build Options menu in your IDE, and set the List file
format to Symbolic. Then re-compile and look at the .LST file. Find the
line for setup_timer_1(), and you'll see the register settings in ASM code. |
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jjacob
Joined: 08 Mar 2008
Posts: 54
Location: PORTUGAL (PORTO)
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| Posted: Sat Jul 18, 2009 5:10 pm |
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No problem
Here is part of my .lst :
| Code: |
.................... setup_ccp1(CCP_PWM); // Configure CCP1 as a PWM
00EA: BCF 05.2
00EB: BCF 03.5
00EC: BCF 05.2
00ED: MOVLW 0C
00EE: MOVWF 15
00EF: CLRF 16
.................... setup_timer_1(T1_INTERNAL|T1_DIV_BY_8);
00F0: MOVLW B5
00F1: MOVWF 10
.................... enable_interrupts(INT_TIMER1);
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It's been a long long time that I don't program in ASM ... and really don't understand what is what 
If you would be so kind and patient to explain me ... I would appreciate.
Thank you for you help
Jacob |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Jul 18, 2009 5:28 pm |
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You didn't put it in Symbolic List file format. It's still in normal CCS format.
But, it doesn't matter. Here's the explanation:
| Quote: | ...... setup_timer_1(T1_INTERNAL|T1_DIV_BY_8);
00F0: MOVLW B5
00F1: MOVWF 10 // T1CON |
It's moving 0xB5 into the T1CON register. Converting 0xB5 to binary
gives: 1011 0101
Look in the Timer1 section of the 12F615 data sheet. It has a section
that describes the functions controlled by each bit in the T1CON register.
Look the binary value above (Bit 7 is on the left, and bit 0 is on the right)
and see what the settings mean.
It's easier if you print that page in the data sheet, and write in the bit
values below the register diagram: 10110101
Then study the explanations below them. |
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jjacob
Joined: 08 Mar 2008
Posts: 54
Location: PORTUGAL (PORTO)
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| Posted: Sat Jul 18, 2009 5:46 pm |
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OK ...
I have in my .lst :
This means that register '1C' (CMCON1 register) is cleared. So :
| Code: |
bit 4 T1ACS: Timer1 Alternate Clock Select bit
1 = Timer 1 Clock Source is System Clock (FOSC)
0 = Timer 1 Clock Source is Instruction Clock (FOSC\4)
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I have bit4 cleared, so, as you said, i have FOSC\4 for timer1 ...
UFFF ... it was 'hard' to understand ... if what i've said is write, i think that i've learned VERY MUCH with this post
Thank you very much ... but please tell me if i'm wrong ...
Jacob |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Jul 18, 2009 6:56 pm |
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| Yes, that's correct. It uses Fosc/4. |
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