Updating HPWM frequently, safe?

[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.
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[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.
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[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,

[Christopher4187]

Old thread but very relevant to my issue.

Can I use HPWM10:

1. On an 18F87J50?
2. And have it glitch free?
3. To make a pulse train that's 140mS long and have varying duty cycles within the pulse train?

In other words: 300uS on, 200uS off, 300uS on on, 200uS off, 130uS on, 370 uS off, 300uS on, 200uS off, 130uS on, 370uS off, 170uS on, 330uS off, 130uS on, 370uS off, etc.

Each bit is 500uS and I don't need to modify anything while the packet is being sent; I can modify right before the next one is sent.