Pls HELP!!! PWM using AVR

[simontheng]

Hey people,

i do need help badly. I'm a AVR idiot, i have been looking for pwm guides for 6 hrs but to no avail.

This is the problem: i'm using Atmega48, i want to generate a pwm wave but i want to have 2 different frequencies at the same time.

can it be done?

many thanks,
may god bless you

 

[simontheng]

pwm using atmega48

Can i use atmega 48 to generate 2 frequencies in a PWM wave?

thank you many thanks

appreciate it

 

[Ian Rogers]

The Datasheet has a pwm function on each timer... So I would expect so...

If you want it in the same wave you'll have to do an external add with an opamp

 

[simontheng]

How do i do it???

 

[Ian Rogers]

For what purpose..

 

[bryan]

Have you looked at the tutorial section in the forums at AVRFreaks. Here is one tutorial https://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=76406

 

[simontheng]

For what purpose..

for frequency shift key purpose, after i generate pwm wave i will output to CB station.

so first step, i may need to generate 2 frequencies of pwm using atmega48

 

[Ian Rogers]

Are you bringing then to one signal? or two separate inputs to the CB?

 

[wkrug]

To generate 2 different frequencies you have to use 2 Timers of an AVR Controller.
The Output is an rectangular signal that will have many harmonic frequencies.
For an DTMF code i would never use such one, ore you spend a Filter after the Output of the PWM Source.
I think the better way is to use an DTMF Chip that will be steered from the AVR.
Probably such one like the MT8880 from MITEL.

 

[simontheng]

Are you bringing then to one signal? or two separate inputs to the CB?

nope, is 1 signal with 2 frequencies

 

[srikanthsamaga]

you can't use a timer instead of PWM?
IMO the above approach will be easy.