5 Replies Latest reply on Jun 12, 2013 4:34 PM by dakn_263916

[PWM] - Changing the Clock Frequency during code execution

userc_43432 Jun 12, 2013 4:34 PM

Hello fellows, I'm here to ask about some special issue that I'm having with the PWM16 Block of PSOC 1. In my application, I have to change the clock frequency of the PWM during the code execution. This is the only thing that I can do in order to reach lower levels of the "Output Frequency". In order words, with a Sysclk freq = 24 MHz the minimum value of the output frequency that I can get is 400 Hz. In my application, I need to sweep the frequency between 100 Hz and 10000 Hz. Do you guys know to do this without changing the Sysclk freq? Thanks a lot for the info!

1. Re: [PWM] - Changing the Clock Frequency during code execution

dakn_263916 Jun 12, 2013 11:32 AM (in response to userc_43432)

Yes, look at the API's int he datasheet, there is one for the period. There are

side effects related to when actual update occurs, read those comments as well.



Regards, Dana.
Like Show 0 Likes(0)

Actions
2. Re: [PWM] - Changing the Clock Frequency during code execution

userc_43432 Jun 12, 2013 11:57 AM (in response to userc_43432)

This kind of API adjusts only the Period Value of the PWM. What I need to set is the Clock Frequency of the PWM, not the Output Clock Frequency. I have tried to find a way to configure the PWM config. Registers to set another Clock Source, but I could not find anything.
Like Show 0 Likes(0)

Actions
3. Re: [PWM] - Changing the Clock Frequency during code execution

JoMe_264151 Jun 12, 2013 2:08 PM (in response to userc_43432)

You may always use a counter as a pre-scaler on a neighboured block. The output of the prescaler can be used as clock input to the PWM. Lowest Count will be divide by two, so you get 12MHz as input to your PWM. Higest count you get with a 16bit prescaler.

Bob
1 of 1 people found this helpful
Like Show 0 Likes(0)

Actions
4. Re: [PWM] - Changing the Clock Frequency during code execution

userc_43432 Jun 12, 2013 2:53 PM (in response to userc_43432)

Thanks a lot for information Bob! I'll try it.
Like Show 0 Likes(0)

Actions
5. Re: [PWM] - Changing the Clock Frequency during code execution

dakn_263916 Jun 12, 2013 4:34 PM (in response to userc_43432)

You can use a timer or a counter, clock it at 48 Mhz (as long as clock not derived

from interal global buss route), and use a period divsior of 0 to n-1. At 0 input

clk is output / 1, and just shifted.



Regards, Dana.
Like Show 0 Likes(0)

Actions

Go to original post