LeafLabs Garden

A place to share, learn, and grow...

1. 

   dapoup
   Member

   Dear all,

   Please find herebelow a bunch of Noob-baked questions, from a newcomer that want everything to be cristal clear before going on.

   I want to do 16bits PWM audio output, using the Timer #1 to do so. First, I set the pin 6 as a PWM output. That's for the sketch setup.

   Then, concerning the Timer Setup:

   1 - Prescaler : This is the division ratio applied to the timer tick clock, right?

   ==> What I inderstand : timer.setPrescaleFactor(1) sets the Timer counting clock to 72Mhz? Or maybe the cristal 8Mhz?

   2 - Overflow : This is the value at the one you overflow, or the salue that the counter is set to when it overflows?

   ==> What I understand : timer.setOverflow(65535) sets the counting to its full range, allowing the PWM to be operated in its full scale?

   3 - Compare : is it this buffer, in PWM mode, that stores the value to be compared to for PWM output?

   ==> What I understand : timer.setChannel1Mode(TIMER_PWM)and timer.setCompare(TIMER_CH1, 32768) should generate a square wave at the output of pin 6 of the board?

   Thanks in advance for your kind highlights on those foggy points (at least, to me...).

   dapoup

   Posted 3 years ago #
2. 

   mbolivar
   LeafLabs

   Note that the clock tree on the Maple is highly configurable. These answers apply only to the Maple's default clock tree configuration (which most people don't mess with).

   1 - Prescaler : This is the division ratio applied to the timer tick clock, right?

   Yes, that's right. So a prescaler of 1 counts at the clock speed, 2 means two clock ticks per timer counter change, etc. A prescaler of 1 counts at the max rate of 72 MHz.

   2 - Overflow : This is the value at the one you overflow, or the salue that the counter is set to when it overflows?

   It's the counter value that causes an overflow. The Maple default is for the counter to reset to zero after it overflows.

   ==> What I understand : timer.setOverflow(65535) sets the counting to its full range, allowing the PWM to be operated in its full scale?

   Not sure what you mean by "full scale". But yes, setting the overflow to that value means you can set the compare to any value between 0 and 65535. 65535 (=2^16-1) is the greatest legal overflow value.

   3 - Compare : is it this buffer, in PWM mode, that stores the value to be compared to for PWM output?

   Yes. The compare value determines the duty cycle. Specifically, the duty cycle is the ratio of the compare value to the overflow value.

   Posted 3 years ago #
3. 

   dapoup
   Member

   Thanks a lot for this clear answer.

   Posted 3 years ago #

RSS feed for this topic

Reply

You must log in to post.