SIMPLE timer trouble

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paulofelora
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Posted by paulofelora: Mon. Feb 27, 2017 - 03:10 AM
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Hi - I'm just trying to get a PWM waveform going.  I have a ATMega328P (on an Arduino Nano) running at 16MHz.  I've set OCR0A to various values to no avail - output PD6 just stays low, looking with an o'scope.  See anything obviously stupid here?

void Timer_Setup(){	
	DDRD = PORTD6;						// set PD6 as timer output
	TCCR0A |= ((1<<WGM00) | (1<<WGM01) | (1<<COM0A1));	// Fast PWM mode
	TCCR0B |= ((1<<CS00) | (1<<WGM02));			// no prescaler
}

thanks! paul

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AVR Microcontrollers, megaAVR and tinyAVR
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paulofelora
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Posted by paulofelora: Mon. Feb 27, 2017 - 03:14 AM
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oops I did change the port direction to DDRD = (1<<PORTD6) - still no joy

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jgmdesign
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Posted by jgmdesign: Mon. Feb 27, 2017 - 04:09 AM
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Try this:

 

DDRD = 0x40;  //set portD,6 to output
// Timer/Counter 0 initialization
// Clock source: System Clock
// Clock value: 62.500 kHz
// Mode: Fast PWM top=OCR0A
// OC0A output: Non-Inverted PWM
// OC0B output: Disconnected
// Timer Period: 2.512 ms
// Output Pulse(s):
// OC0A Period: 2.512 ms Width: 2.512 ms
TCCR0A=(1<<COM0A1) | (0<<COM0A0) | (0<<COM0B1) | (0<<COM0B0) | (1<<WGM01) | (1<<WGM00);
TCCR0B=(1<<WGM02) | (1<<CS02) | (0<<CS01) | (0<<CS00);
TCNT0=0x00;
OCR0A=0x9C;
OCR0B=0x00;

Untested

 

Jim

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Bronze Marktheusch
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Posted by theusch: Mon. Feb 27, 2017 - 02:06 PM
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Is this part of an Arduino sketch?  Arduino does default setup of timers.  All of your |= just adds on to how the timer is already set, and indeed you may not get what you expect.

 

 

You can put lipstick on a pig, but it is still a pig.

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paulofelora
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Posted by paulofelora: Mon. Feb 27, 2017 - 03:25 PM
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Ahh thanks gentlemen, I will try Jim's setup tonight.  No, this is straight C - the hardware is Arduino clone, tho... paul

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Bronze Marktheusch
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Posted by theusch: Mon. Feb 27, 2017 - 03:36 PM
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I don't think you want mode 7, do you?  If you do mode 7 with OCR0A as TOP, then OCOA output may well be uninteresting.  You could set up for PWM on the second channel, using OCR0B as the duty cycle for the PWM on OC0B.

 

Perhaps start with mode 3.  (fixed TOP of 0xff)  And indeed get rid of the |= to make us respondents happier, especially when only showing a fragment.

 

 

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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paulofelora
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Posted by paulofelora: Mon. Feb 27, 2017 - 03:55 PM (Reply to #6)
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Theusch - good point, will try it tonight - paul

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paulofelora
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Posted by paulofelora: Tue. Feb 28, 2017 - 01:02 AM
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Major Deuippe here - I wasn;t running my Timer_Setup code!!  Thanks all for your help, paul

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