external oscillation

[mister_e]

Yup PWM is the way to go. You can use the PBP HPWM or setting the PIC register as Sayzer said.

mister_e, pls correct me if I am wrong

I got the same results

[lerameur]

I got it going with a 4Mhz oscillator. Here is the program.
I wanetd to use the 20Mhz oscillator. and it do not work. I change the 4 to a 20 in the program and changes the crystal and the capacitor to 22pF and it is not oscillating, anybody knows why. is there a command I nee to do ?


Define LOADER_USED 1
DEFINE OSC 4 'Using 4MHz oscillator
TRISB = 0

loop: FREQOUT PORTB.1,10000,20000 ' Turn on PORTB for 1- sec at20Khz
Pause 100 ' Delay for .5 seconds

Goto loop ' Go back to loop and blink LED forever

[lerameur]

ok added this line :

@ DEVICE HS_OSC

and now it works

[lerameur]

I am trying ot get a sin wave at the output. From the manuals of picbasic pro, they say to add a low pass filter, I did this, it dos remove the extra noise, but it does not make it a sinwave. Anybody know how to make it a sin wave ?

ken

[sayzer]

Did you check this post?

http://www.picbasic.co.uk/forum/showthread.php?t=718



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[mister_e]

If it's for a single frequency with a 50% duty cycle you could still use a pair of integrator made with Op-Amp.

[lerameur]

I need 6 frequencies.
maybe using an analog circuit using amplifiers to make the oscillation and the pic to control + / - a few kilohertz to get lets say between 20 to 30 khz ??
The goal of this is to create an ultrasonic bird repeller, maybe the square waves (although noisy) can scare them off.

k