My first foray into PWM

[Amoque]

You might, if you have one laying around, use a clock divider chip... or a counter... Here's a link that explains my thinking better than I can.

[richard]

You might be able to achieve something using compare mode and the external clock pin for timer1. if you have enough spare pins and if you were really clever
use the hpwm output to drive tmr1ck then you could change the flash rate on the fly

[Demon]

Euh, I think I'll just get back to finishing my Charlie-plexing work for now. LOL

Thanks though, I will have to jump into PWM one day, hopefully next summer.

Robert

[HenrikOlsson]

Hi Robert,
In your first post you say LED ON for 500uS, OFF for 500uS but then you say you want a period of 1s - that's a difference of $03E8 times.
I know you didn't want to do it with an normal interrupts but I'm going to suggest a simple timer interrupt anyway.... At such low frequencies (even though you're probably not going to get 500ms interrupt period in "on go") the interrupt processing will have very little impact on the overall performance.

/Henrik.

[gadelhas]

Hi Robert;

An HeartBeat Led should be do it with a timer interrupt like Henrik sujested....
If you cannot achieve tht time that you want, you do for instance, a 100ms interrupt and with a counter you can achieve the time that you want counting in 100ms spaces.
You can count 5 x 100ms and then toogle the led.

[Demon]

Hi Robert,
In your first post you say LED ON for 500uS, OFF for 500uS but then you say you want a period of 1s - that's a difference of $03E8 times.
...

(without considering oscillator speed and PWM range limitations)

Then there's something about PWM that I didn't understand. HIGH/LOW using PAUSE for 500uS is not the same as a 1000uS period with 50% duty cycle?


Ooop, uS, not Us.

Robert

[gadelhas]

(without considering oscillator speed and PWM range limitations)

Then there's something about PWM that I didn't understand. HIGH/LOW using PAUSE for 500uS is not the same as a 1000uS period with 50% duty cycle?

Attachment 7531
Ooop, uS, not Us.

Robert

Yes, from that point of view, it is the same thing! (without considering oscillator speed and PWM range limitations)

[HenrikOlsson]

Then there's something about PWM that I didn't understand. HIGH/LOW using PAUSE for 500uS is not the same as a 1000uS period with 50% duty cycle?

Yes of course, 500us ON and 500us OFF is 50% dutycyle. But the period is 500us+500us = 1000us = 1ms = 0.001s - NOT 1s which you later wrote.

In your first post you indicated you wanted a PWM period of 1000us (a frequency of 1000Hz). In your second post you said you wanted a period of 1s (a frequency of 1Hz). It doesn't add up - that's all I was trying to say.

/Henrik.