need help for frequency acceleration and deceleration

The basic idea is to use a counter. Load it with zeros. Let it count up until it rolls over - set your output signal to '1'. Repeat the load and count process, and when it rolls over this time, set your output signal to "0". You've just generated one clock period.

Now load your counter with "1", and repeat the above process - you'll generate another clock period, but it will be one count shorter than the first.

Now load the counter with "2", generate another clock period, and keep incrementing the counter load value until you get up to your highest value of 150KHz.

You may need more than one level of counter to get the frequencies you want, depending on your clock speed, and the resolution you want, etc.

Or, you can do the same thing but load the counter with a large value and count backwards to zero, and set the output signal when the counter hits zero. Same thing.

There is a good application note on PWM at the Microchip web site, if you do a little searching for it.

Let's think about what you are asking.

1. You will have to interrupt early frequencies, since your maximum sweep time is 500 ms. (You will no be able to do a complete 1 Hz cycle in 500 msec. ; you will never complete a 0 Hz period).

2. Is it a sinewave or a square wave you are interested in sweeping?

3. If you think interrupting is NOT ok, then you have to do a series calculation for best fit sequence of periods.

I need more information on restraints to be of more help. Hopefully, you wil re-think the problem to get better specification.