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STM32: DMA and .. timers ???

Hi all,

I am learning about the stm32f1xx devices, trying out some example-codes on using DMA with the ADC and DAC.

However, when reading the information in the reference-manual about DMA, it mentions DMA in combination with Timers!

Now, I am a bit confused. As far as I understand it, the DMA is there to transfer data between devices (ADC, DAC, USART, SPI, I2c) to memory without using the CPU.

But where do do the timers fit in? I understand that timers are needed to generate events (e.g. to trigger the start of a ADC or DAC process), but that does not involve any RAM, no?

Or do I have a to-simple view of timers?

Cheerio! Kr. Bonne.

Reply to
kristoff
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Hi

You can use for example byte or long DMA transfers to set the timer reload or compare capture values without CPU interaction.

A couple of years ago I did a digital power supply in which the error signa l from the error amplifier controlled the peripheral PWM duty cycle via DMA . That way I saved an external PWM controller and added the possibility to control the PWM for special functions also

You could sample with the ADC and control timer frequency the same way with no CPU load

Cheers

Klaus

Reply to
Klaus Kragelund

Klaus,

(Now reply in the group insyead of via direct email).

2nd try! :-)

On 20-11-15 00:18, Klaus Kragelund wrote: > You can use for example byte or long DMA transfers to set the timer reload or compare capture values without CPU interaction. > A couple of years ago I did a digital power supply in which the error signal from the error amplifier controlled the peripheral PWM duty cycle via DMA.. That way I saved an external PWM controller and added the possibility to control the PWM for special functions also > You could sample with the ADC and control timer frequency the same way with no CPU load

Nice!

Looks I still have a lot to learn about microcontrollers!

Cheerio! Kr. Bonne.

Reply to
kristoff

The ST parts are pretty fancy.

I'm fairly sure that you could also use the DMA with a timers capture feature -- each time an event happens on a capture input, the time would be recorded into memory for later perusal.

But -- you'd have to check and see.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com
Reply to
Tim Wescott

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