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Re: Tiny AVR
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The application needs to monitor sensor pulses that can come in at any
time.  I don't think we can afford the sleep/wake delay.



Re: Tiny AVR

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The application needs to monitor sensor pulses that can come in at any
time.  I don't think we can afford the sleep/wake delay.

Easy... put the TINY in sleep mode (1uA) and wake it up on the pulses using
PCINT
(Pin Change Interrupt, pos or neg edge, or both). Do your processing ASAP
then go back to sleep. Simples :)



Re: Tiny AVR
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But it could miss some pulses while waking-up.  We need to count every
pulse.

Re: Tiny AVR
linnix a crit :
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You mean your pulsed _fast_ clocked uC won't react faster that that your
wanted LF clocked permanently running at 32KHz?

How fast are those events you want to catch? How many in line, and how fast?

--
Thanks,
Fred.

Re: Tiny AVR
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Probably not.

But we can run it in idle mode (with hardware counter running) at
32KHz, perhaps with 2uA.


Re: Tiny AVR
.
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Probably not.

But we can run it in idle mode (with hardware counter running) at
32KHz, perhaps with 2uA.

But you can run at 9.6MHz in sleep @1uA and capture a 1KHz signal, do some
processing and go back to sleep and be at 2uA average... If you can capture
it at 32KHz ck, then where's the problem? Use the int RC osc and divide by 8
and you're even better off



Re: Tiny AVR
responding to http://www.electrondepot.com/embedded/tiny-avr-123061-.htm

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Atmel provides formulas for calculating the time it will take it to resume
processing based on power-down or power-save and the clock source. It's
something like 20 clocks + 4ms or 20 clocks + 64ms (if you can't trust
your power source to stabilise quickly). You get to pick 4 or 64ms delay.
Sounds like you would want 4ms. You can even further reduce that to just
20 clocks (or approx 60us, says Atmel) if you enable brown-out detection
(BOD) but that will increase power consumption in sleep mode. I don't know
how much - didn't get to play with it yet. So, it looks like you get a
choice of waking up time from 60us to 4.06ms based on power consumption
you can afford.  

You will just have to quantify the input and, really, there's no way
around it anyhow - you do need to know how fast the pulses you're counting
are arriving. What if they arriving too fast for the MCU to count anyway?
If all you're doing is incrementing a counter, you may be talking about
microseconds between interrupts. Maybe you can make it stay awake for a
millisecond to catch fast-coming bursts of inputs, then put it to sleep
when things quieted down for, say, longer than 1ms. Sort of like switch
de-bounce?

What type of sensor is this, anyhow?

-------------------------------------
 /\_/\
((@v@))
():::()
 VV-VV



Re: Tiny AVR
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It's a variable speed rotational sensor, close to 50% duty cycle.
This is the little brother watching the sensor and waking up the big
brother if necessary.  So, at long as we can keep the hardware counter
on and processor idle at 1uA or 2uA.  We should be OK.  Pulse
processing at higher clock speed might work, but not necessary better
power savings.

Re: Tiny AVR
responding to http://www.electrondepot.com/embedded/tiny-avr-123061-.htm

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Variable reluctance rotational speed sensor? What RPMs are expected?

I'm just curious: couldn't you harvest some power from its output,
trickle-charge a big cap (supercap?) and only put the MCU to sleep when
the RPMs are too low to charge the cap and don't require fast processing
anyway?

I actually don't even know if they make digital VRSes  - you were talking
about *pulses* and this might only work with an analog output one.

-------------------------------------
 /\_/\
((@v@))
():::()
 VV-VV




Re: Tiny AVR
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Variable magnetic rotational sensor.  Perhaps 100s Hz.

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Actually, we need to provide some power to the sensor.  Can't pull
much power out of the output.


Re: Tiny AVR
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maybe he is trying to digitally maintain the position information of a
device that has a A+B channel generating device on it.


  Jamie



Re: Tiny AVR
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does he sensor generate power or consume it?
is there enough innertia to switch modes during spin-up?

--
⚂⚃ 100% natural

---

Re: Tiny AVR
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We probably need two sensors.  A passive triggering sensor (very
little current) to signal the controller and to turn on the measuring
sensor (several mA).


Re: Tiny AVR
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But it could miss some pulses while waking-up.  We need to count every
pulse.

Is the pulse going at >1MHz??



Re: Tiny AVR

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It won't miss anything.

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We have failed to address the fundamental truth that endless growth is  
impossible in a finite world.
 

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