Updating HPWM frequently, safe?

[Samoele]

Hello,

I would have two different frequency on CCP1 and CCP2 pin the first is 100HZ and second is 20Khz-40KHz. I use 1MHz quartz for clock and HPWM10 command from D.T. I use PIC16F876.
I have on both CCP pin HPWM10 command with frequency 100hz and different duty. This working ok. When changed frequency on CCP1 to 1KHz then is frequency on both pin unchanged and very unstable
When change one HPWM10 command to normal 8 bit HPWM then stay result unchanged.
what I did wrong?

here is first part of my program:




INCLUDE "ALLDIGITAL.pbp"

Cifra var byte
Cifra1 var byte
Maska1 var byte
Maska2 var byte
W var byte
i var byte
time var byte
PR var byte
VU var word
VD var word
Duty VAR word
Duty1 VAR word
FREQUENCY var word
FREQUENCY1 var word

LED var PORTC.4
LEDDis1 var PORTA.0
LEDDis2 var PORTA.1
tipka1 var porta.2
tipka2 var porta.3
tipka3 var porta.4
BUZ var porta.5
enable1 var portc.0
b0 var byte
b1 var byte
b2 var byte
b3 var byte
impulz var WORD
minuta var byte
key var byte
pavza var word

bp var byte

TRISA=%11111100
TRISB=%00000000
TRISC=%00000000


clear
include "HPWM10.pbp"
LOW PORTC.1
LOW PORTC.2
PWM_ON CON %00001100
PWM_OFF CON 0
time=6
FREQUENCY=93 '
FREQUENCY1=1000
low led
gosub zvok
eeprom 0,[31]
eeprom 2,[55]
high enable1
high led
pause 100
low led




INTCON = %00100000
OPTION_REG = %10001000

On Interrupt Goto ISR
INTCON = %10100000
w=0


Main:

gosub tipka
gosub timing
read 0,b2
gosub tpwm
@ HPWM10 2,_IMPULZ,_FREQUENCY
read 2,b0
gosub ppwm
@ HPWM10 1,_duty,_FREQUENCY1
Gosub Priprava
goto Main

ppwm: b1=b0-50
lookup2 b1,[100,200,300,400,500,600,700,800,900,1000],duty
return

tpwm: b3=b2-30
lookup b3,[0,31,16,6,21,46],duty1
return

[Darrel Taylor]

With 16F876's, both CCP modules use the same Timer in PWM mode (TMR2).
If you change the frequency of one, the other one changes too.

With a 4 Mhz crystal, the minimum HPWM frequency is 245 Hz.
Since you are using a 1 Mhz crystal, you can get down to 62 Hz, but you have to specify the frequency as if it were running at 4 Mhz.

If you want 100 Hz, then specify 400 Hz in the HPWM10 command.
93 is way below the minimum.
<br>

[Samoele]

Frequency of 100 Hz is not a problem. In the case that I use PIC16F886 asking whether the command HPWM10 set timer TMR1 and TMR2 for each channel?
Can you write the registry settings for the PIC16F886?

tnx
Samo

[Darrel Taylor]

Even on a PIC16F887, the CCP modules can only use Timer2 in PWM mode.
So both PWM channels will operate at the same frequency.

So I guess the answer to your question is ...
HPWM10 only changes Timer2, not Timer1.
<br>

[jamie_s]

Darrel,

Whats required to have 'glitch free' operation but with 8 bit PWM, can the include file be easily modified for 8 bit, or should i just multiply my desired 8 bit dutycycle by 4?

[jamie_s]

Also, just testing on 16F887, at 4mhz,

@ HPWM10 1,_OUTDUTY,300 results in a PWM frequency of 10khz according to my o'scope ???
I see the duty cycle changing, but the freq is around 9-10khz?

[Darrel Taylor]

The frequency must be a variable.
You can't pass a constant as the parameter.

And just shift left 2 (<<2) to use 8-bit values.

hth,