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alyeomans
Joined: 26 Feb 2014
Posts: 24
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| PIC184620 Enabling INT_TIMER3 stops CCP2 PWM output |
 Posted: Tue Aug 26, 2014 11:46 pm |
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Hi All
I am using the the CCP2 pin as a PWM output. The PWM signal disappears as soon as enable_interrupts(INT_TIMER3) is called.
The output of CCP2 has been changed from RC1 to RB3 with fuse CCP2B3.
The datasheet says that TMR2 is used.
Any clues would be welcome.
Thanks in advance.
Alex
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Aug 27, 2014 11:15 am |
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The program below produces PWM output on Pin B3. Enabling
#int_timer3 interrupts doesn't affect it at all. It works.
Last night, you briefly posted that it failed if #int_rb was enabled. I tested
that, and it also works in that case.
If you want help, you need to post a test program that shows the failure.
You also need to post your CCS compiler version. Also tell us how you
know the PWM fails. ie., are you looking at Pin B3 with an oscilloscope ?
I'm testing it in hardware with a scope and with compiler vs. 5.026.
Test program:
| Code: |
#include <18F4620.h>
#fuses INTRC_IO,NOWDT,PUT,BROWNOUT,CCP2B3
#use delay(clock=4M)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#int_timer3
void timer3_isr(void)
{
static int8 count = 0;
count++; // Increment a variable on each interrupt
}
//=================================
void main()
{
// Setup for 3.9 KHz pwm frequency with 4 MHz oscillator.
setup_timer_2(T2_DIV_BY_1, 255, 1);
setup_ccp2(CCP_PWM);
set_pwm2_duty(128); // 50 % duty cycle
clear_interrupt(INT_TIMER3);
enable_interrupts(INT_TIMER3);
enable_interrupts(GLOBAL);
while(1);
} |
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alyeomans
Joined: 26 Feb 2014
Posts: 24
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| Posted: Thu Aug 28, 2014 1:10 am |
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Hi PCM programmer, Yes, that first post was a mistake. I became lost in testing and enabled some commands which led me down the wrong path.
I can confirm that the timer3 works okay in the reduced test program. When I introduce the code into the TMR3 ISR which is used for button polling and debounce that is where the problem resides.
| Code: | #INT_TIMER3
void timer3_isr(void) {
//poll key change and debounce
if(kb_scan_count>=2){
byte changedKeys;
newKeys=input_b() & 0b01110000; //read current keys B4,5,6 with input mask
changedKeys=oldKeys ^ newKeys; //XOR with oldKeys to identify changed keys
//Test for the changed key no longer being set
//SW1
if (bit_test(changedKeys,4) && !bit_test(newKeys,4)) {
keyPressed=1;
}
//SW2
if (bit_test(changedKeys,5) && !bit_test(newKeys,5)) {
keyPressed=2;
}
//SW3
if (bit_test(changedKeys,6) && !bit_test(newKeys,6)) {
keyPressed=3;
}
oldKeys=newKeys; //load current keys to old keys
kb_scan_count=0; //reset count
}
//inc counters
kb_scan_count++;
} |
If I comment out the line with | Code: | | newKeys=input_b() & 0b01110000; |
All works
_________________
I type therefore I press buttons |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Aug 28, 2014 9:11 am |
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input_b() changes the TRIS to be all input pins on PortB. This is the
source of your problem. Pin B3 (PWM output) must be kept as an
output pin.
The 184620 data sheet says:
| Quote: |
15.4 PWM Mode
In Pulse-Width Modulation (PWM) mode, the CCPx pin
produces up to a 10-bit resolution PWM output. Since
the CCP2 pin is multiplexed with a PORTB or PORTC
data latch, the appropriate TRIS bit must be cleared to
make the CCP2 pin an output.
|
and
| Quote: | 15.1.2 CCP2 PIN ASSIGNMENT
Changing the pin assignment of CCP2 does not
automatically change any requirements for configuring
the port pin. Users must always verify that the appropriate
TRIS register is configured correctly for CCP2
operation, regardless of where it is located. |
Solution:
Add the input_state_b() function (shown below) to your program and put
it above main(). Then call it in your #int_timer3 routine, instead of the
input_b() function:
| Code: |
// This function reads Port B without changing the TRIS.
int8 input_state_b(void)
{
#byte PortB = getenv("SFR:PORTB")
return(PortB);
} |
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alyeomans
Joined: 26 Feb 2014
Posts: 24
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| Posted: Thu Aug 28, 2014 7:43 pm |
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Thank you PCM programmer Program works perfectly.
Your help has been valuable and high appreciated. Thank you again.
Alex
_________________
I type therefore I press buttons |
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