What timer were you using in the simulator? I'm
using T0 in the 168 and I can load it & introduce an interrupt. The
interrupt is cleared but there is no vector to the ISR.
Dennis
----- Original Message -----From: Loren BoyleSent: Wednesday, November 09, 2005 5:56 PMSubject: Re: [AVR-Chat] Phase and Frequency Correct PWM on a Mega 8
Hi Martin.
I played with PWM on the Mega 8 for hours on the simulator trying to find what I was doing wrong. I finally found somewhere that the PWM does not work for the Mega 8 (or even the 168) with the simulator(studio 4). I finally did what I thought must be right and stuck it in the chip and it worked correctly.
Good luck
Loren
Dave Hylands
Sent by: AVR-Chat@yahoogroups.comNov 09, 2005 03:35 PM Please respond to
To
AVR-Chat@yahoogroups.com
AVR-Chat@yahoogroups.com cc Subject Re: [AVR-Chat] Phase and Frequency Correct PWM on a Mega 8
Hi Martin,
> I'm having what I can only classify as annoying. I implemented a simple servo controller with a tiny 15 ( two position ) and it worked perfectly. I've also done some simple PWM stuff with Timer 2 on the Mega 8. Now, however I need to use the 16 bit timer to generate PWM. I need a bare minimum of 12 bits precision but more would be better ( 256 servo positions, 60 Hz update rate ). To that end I've tried to get 16 bit phase and frequency correct PWM working and I've had no luck. In the simulator the timer counts up to TOP (in my case 0xFFFE ) and promptly overflows to zero. Now it's my understanding that it is supposed to count up then down ( certainly that's how it works in 8 bit mode ). It wouldn't bug me so much, it overflowing, if I was able to get something useful out of it. However because it is overflowing the output pin is only getting set or cleared ( depending on the setting of the COM1nX pins ). Following is the code I use to initialize it.
I wrote some code for the ATMega128 which uses Timer3, but it should
work on Timer1 with a minor tweak (changing the SERVO_1 and SERVO_2
definitions to be 1A and 1B rather than 3A and 3B).. It uses the Fast
PWM mode runs the timer at 2MHz, which means it will overflow every
32.7 msec (or 30.5 times per second).
The sample code can be found here:
You'll be prompted for a username and password, use the word gumstix for both.
To get the complete example to build, you'll need the Common
directory, the Simple-Servo directory, and the Rules.mk file.
--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/
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