Low frequency generator

[Acetronics2]

Why not easily generate 1000 - 25000 Hz ( straight with PBP ...) and use a , say, CD 4518 or 74LS390 as a 100 divider on the output ...

as duty cycle is supposed to always be 50% ... no problem then !

Alain

[mark_s]

If you can't make your pic16f88 work. The pic18f2431 with a 4mhz clock can output a pwm about 2hz using the power control pwm module. I know you said simple, but simple isn't always easy.

[lerameur]

I need to control frequency and Duty cycle (I mentioned earlier 50% Dutycycle cause I can easily get any Dutycycle the problem is frequency, but variable dutycycle is better) . I also want to output the frequency and dutycycle on a LCD.I had this thin g going out high and low pins.... but obviously LCDout played a destructive role in the timing. ...
I will check out all the possibilities and the power control pwm module with the F2431

[Demon]

Going out on a limb with this.

PIC 1 outputs signal on a pin, PIC 2 reads signal and displays on LCD, interrupt on 4 input pins on PIC 1 adjust duty and frequency. This way the LCDOUT doesn't interfere with the pwm.

Can we even read PWM signals with PICs (never even got close to doing this)?

Robert

[lerameur]

HUmm.. two pics.. well
I thought about going to a waveform chip like the ICL8038.. but I wanted a more 'modern' solution going with a single Pic,
I am going try tonight what Henrik mentioned above.

K

[lerameur]

I tried different value of PR2, (had tried it before..)
Still am getting 60Hz at PR2 255 and at 200 I get 77hz at 100 I get a steady 5v out...
Here is the link of the program I use for mytest: http://www.warburtech.com/products/compilers/picbasic.pro.compiler/sample.code/hardpwm.pbp/

[lerameur]

I was playing around with internal frequency, just to let you know that it do not work. Decreasing the int freq to 500Khz decreases the min freq to 30Hz but also the max freq at 130Hz !!

K

[rmteo]

I tried different value of PR2, (had tried it before..)
Still am getting 60Hz at PR2 255 and at 200 I get 77hz at 100 I get a steady 5v out...
Here is the link of the program I use for mytest: http://www.warburtech.com/products/compilers/picbasic.pro.compiler/sample.code/hardpwm.pbp/

That is not your only issue. Because you are dealing with reciprocal values, granularity (resolution) is going to be very poor throughout. At high PR2 values, you will see very little change in frequency - eg. reducing PR2 from 255 to 254 you may not be able to detect any change in frequency. However, at the other end of scale, incrementing PR2 will result in a huge change in frequency.