Could anyone told me How to make the timer work on the PWM mode?

LeafLabs Garden » Support » Maple Hardware Support

Could anyone told me How to make the timer work on the PWM mode?

(7 posts) (3 voices)

Started 4 years ago by gulu2065
Latest reply from gulu2065

gulu2065
Member

I want the timer work at the PWM mode and produce a 1.6Mhz frequency.

This is the code I write.
However, it do not work correctly and only produce a 549.5 Hz frequency.
which is the initial PWM frequency, I guess. The timer do not work.
Could anyone told me how to fix it?

#include <timer.h>
HardwareTimer timer(4);
void setup() {
pinMode(0, PWM);
pinMode(24, PWM);
pinMode(28, PWM);
Timer4.pause();
Timer4.setPrescaleFactor(1);
Timer4.setOverflow(45);
Timer4.setChannel4Mode(TIMER_PWM);
Timer4.resume();
Timer4.refresh();
}

void loop() {

}

Posted 4 years ago #
gulu2065
Member

Anybody can help?
Thanks!

Posted 4 years ago #
robodude666
Member

I would recommend looking at the PWM documentation, and more specifically the pwmWrite function.

The pwmWrite function is similar to analogWrite, except that it uses the STM32's full 12-bit capability. The duty cycle is based on a value from 0 to 65535. Setting it to 32767 will give you a roughly 50% duty cycle. If you desire a different frequency, the documentation describes how it can be changed as well.

Posted 4 years ago #
gulu2065
Member

robodude666, Thanks.
Do you mean the timer.setPeriod(). But with this I could only reach a low frequency, maybe at most 1Mhz.
Do you know how to configure the timer directly on the PWM mode and produce higher frequency I want?
Thanks

Posted 4 years ago #
poslathian
LeafLabs
gulu, you should be able to use the setPeriod function to get very high output frequencies. Something like 1.6MHz should be doable. First, find out what timer the PWM pin you are using is attached to. For example, for Maple, this table is here: http://leaflabs.com/docs/hardware/maple.html#maple-timer-map

If you were using Pin 6 as your output, you can see from the table that this is attached to Timer1, channel 1.

To get the timer running *really* fast, use the "setPrescaleFactor" function:
Timer1.setPrescaleFactor(1);

That should get the timer going at 72MHz.

Now, lets say you wanted a 50% square wave at 1.6MHz, 72MHz/1.6MHz = 45, conveniently an even number! So set your overflow to 45

Timer1.setOverflow(45);

Notice that since we overflow at 45, your max PWM value will be 45, not 255 or 65535! Assuming you set pin 6 in pwmOutput mode, you should be able to just do pwmWrite(22) to get your 50% wave at 1.6MHz. To manually set this up, you could do:
```
Timer1.setMode(TIMER_PWM);
Timer1.setCompare(1,22);
```
Let me know if this works as I didnt actually run this!
Posted 4 years ago #
gulu2065
Member

poslathian
I have got 1.6Mhz signal with your code.
Thanks a lot.
Here is the code. I hope could help others!

Posted 4 years ago #
gulu2065
Member

HardwareTimer timer(1);
void setup() {
pinMode (6, PWM);
Timer1.setPrescaleFactor(1);
Timer1.setOverflow(44);
Timer1.setMode(TIMER_CH1,TIMER_PWM);
Timer1.setCompare(1,22);
}
void loop() {
}

Posted 4 years ago #

RSS feed for this topic

Reply

You must log in to post.