Mega 8515 pwm

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I am working on a custtom multi-meter and the a/d chip needs 32khz as a clock. I have 8mhz on the 8515 and figured the pwm could easily give me the 32khz. Does anyone have anything in assembler I could play with?

I am hoping it can run without an interrupt service

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

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Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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You dont need PWM, because you don´t want to change the duty cycle.
You don´t need an ISR either. Just set up a timer and the rest will be done by hardware.

Set up the timer for CTC mode, and "toggle" the output OCn.
The frequency should be set up with an appropriate timer and the TOP value of the timer.

Klaus
********************************
Look at: www.megausb.de (German)
********************************

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Ok, I shall look at that

Thanks

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Mr. Mega..........

Damn that works great!!!

Thanks :lol:

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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small problem with the solution

I noticed that the counter running in CTC mode increments the counter twice per clock cycle.

Is this normal?

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Quote:

I noticed that the counter running in CTC mode increments the counter twice per clock cycle.

I don't think so, Tim. How have you noticed this?

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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Mind you i notice this in avrStudio during simulation.

When the application runs realtime I noticed that the toggle is half the calculation.....let me explain

I am running a mega8515 at 3.686mhz. I want 32.768khz on the ocr0 output. there is no prescaler. I calculated that 3.686mhz divided by 32.768khz is 112.4(112 rounded). When I placed 112 in the ocr register, and ran the code realtime, the ocr output is 16khz. when I halfed 112 to 56, I get the frequency I am looking for.

Very strange

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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That would be correct. Remember that you are looking for a >>frequency>>. If you want a symmetrical waveform with frequency of 100Hz, you have to toggle the pin 200 times per second.

Side note: In CTC, both 0 and TOP are counted. So you normally calculate the number of clocks and then need to subtract 1 to get the OCR value. In your case you were close to half so it didn't matter.

An alternate method would be to set up a PWM with TOP at 112, and an OCR value of 56.

[A tool that I use all the time as a calculation aid is "avrcalc". Do a site search on that. Others have also developed and posted similar tools.]

Lee

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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Hint: RTFM.

here are all the formulas to calculate the frequency.
CTC mode "toggle": page 107. Here you can see the "2x" and the "1+".

Klaus
********************************
Look at: www.megausb.de (German)
********************************

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ok, Thanks guys

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user