16 bit PWM using CCP1

[Acetronics2]

Hi, Talatsahim

First have a look to how PBP shares its variables with asm ...

Alain

[Archangel]

Hi, Talatsahim

First have a look to how PBP shares its variables with asm ...

Alain

_WhatsThat ?

[Dave]

For starters, There is NO 16 bit compare register for PWM use. The upper byte is shared with a few other bits of config. There is ONLY 10 bit's available for PWM use in hardware. Read the data sheet for the processor you are using.

[talatsahim]

Thanx Dave,

I use 10 bit hardware PWM. But I need more resulation. I such a little trick

Talat

[Dave]

What Acetronics2 is trying to say is, when accessing PBP variables inside of an ASM routine you need to prefix an underscore before the variable name such as "movf _PWM_VAL,W ; lb"
As far as getting more resolution from the PIC processor, Your out of luck. You can always build your own digital pwm circuit with hardware if you are so inclined.

[talatsahim]

Hi Dave,
This is just copy-paste error..
What's interesting is that, these codes do not work to as 8-bit (10 bit too)
Thanx

[HenrikOlsson]

Hi,

As far as getting more resolution from the PIC processor, Your out of luck.

So, Microchip themselves and previous posters in the this thread (Darrel, Bruce, Norm) are wrong then, what am I missing?

When using the CCP module in PWM mode it's limited to 10bits resolution. But if you use it in compare mode, the way that the application note describes you can get 16bit resolution but:
1) You won't be able to get 100% dutycycle
2) The maximum output frequency will be limited to ~122Hz @32MHz.
3) You'll get some CPU load from the interrupt processing.
4) You need to deal with assembly code in the ISR (or deal with more "CPU load" if using DT-Ints)

/Henrik.

[EarlyBird2]

What Acetronics2 is trying to say is, when accessing PBP variables inside of an ASM routine you need to prefix an underscore before the variable name such as "movf _PWM_VAL,W ; lb"
As far as getting more resolution from the PIC processor, Your out of luck. You can always build your own digital pwm circuit with hardware if you are so inclined.

But Darrel did not do this in his code, prefix with "_". Also as Talat has said he is following Darel's example for "16 bit PWM using CCP1" which obviously worked for Darrel, Bruce and Norm.

So Talat 16 bit PWM is possible. I have read the whole thread and the datasheets for the 18F452 and the chip you are using 16F1827.

The first possible issue Darell said his code was for 18F's only in post 3 does anyone know why not 16F's? The 16F has CCPx compare mode.
With regard to the 16F1827 I think CCP4 has the required features needed and CCP1 does not but I need more time to re-read the datasheet but in the meantime it would be helpful if some one could confirm which CCPx should be used.

[EarlyBird2]

The first possible issue Darell said his code was for 18F's only in post 3 does anyone know why not 16F's? The 16F has CCPx compare mode.
With regard to the 16F1827 I think CCP4 has the required features needed and CCP1 does not but I need more time to re-read the datasheet but in the meantime it would be helpful if some one could confirm which CCPx should be used.

Having dealt with the "_", wild goose chase, which had nothing to do with the problem any ideas?

[talatsahim]

Hi, Acetronics2

This is part of code. Variable sharing, what is wrong?

Thanx