AVR + LCD + battery power

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Is it possible to create a BATTERY powered LCD clock with AVR? I need at least 4 digits with 7 or 8 segments in each one (most probably static, without multiplexing) and 25 μA max consumption.

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PS. Is it possible to use an external LCD driver with AVR? And is there such driver with 1..5 μA consumption? I do not want to switch to texas instruments...

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Quote:

PS. Is it possible to use an external LCD driver with AVR? And is there such driver with 1..5 μA consumption? I do not want to switch to texas instruments...


Aren't you jumping ahead in your assumptions?

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Is it possible to use an external LCD driver with AVR?

Why wouldn't it be possible with an AVR, if it is possible with other microcontrollers? What microcontroller features would enable or preclude use of an "external LCD driver"?

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And is there such driver with 1..5 μA consumption?

Now, you've just jumped ahead from the previous sentence...there is no room in answering your questions to address/suggest using the AVR series built for the task, with integrated LCD driver.

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I do not want to switch to texas instruments...

What does that have to do with the price of tea in China? What inferences must we make in order to grasp the intent of that statement? Is there a problem in your religion with purchasing TI products? Does it mean you are choosing between Atmel AVR and TI ??? (MSP430?) Or choosing a TI LCD driver? Or what? Is there a reason for this "threat"? Because of power consumption? Or built-in LCD driver?

Short summary is that till you get good enough to design for/measure a few nA of draw, you are going to get comparable results between TI MSP430 and Atmel AVR in the type of app that you described.

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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Quote:

I need at least 4 digits with 7 or 8 segments in each one

So you aren't going for a standard HD44780 driven module with alph character support but for a mega169 or similar and a direct drive glass? If so which glass?

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Quote:

I need at least 4 digits with 7 or 8 segments in each one (most probably static, without multiplexing)

Which brings me to another curiosity: Why "most probably static"? Is there a particular model of LCD that needs to be used? If so, then why "most likely"? If not, why the requirement?

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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(most probably static, without multiplexing)

Ah I missed that - so a plain glass and a 169 sound like they are off the menu then?!? Are you talking about bistable LCD when you talk of "static" then? Anything else DOES need regular refresh cycles. bistable also has the advantage of maintaining the display with power removed ("e-paper").

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Quote:
I need at least 4 digits with 7 or 8 segments in each one (most probably static

Most probably only m3290 and m6490.

No RSTDISBL, no fun!

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Quote:
Are you talking about bistable LCD when you talk of "static"

No, just one common wire without MUXing.

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Possibly "electronic paper" indicators may fall into the focus - these do require power only when changing the display. Shall make 25 microAmps average consumption feasible. Not sure about driving details for these, though.

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3.5/4/6 digit non-multiplexed LCDs can be readily found at regular distributors. Without multiplexing you don't need a LCD driver at all; just plenty of outputs, one for each segment and one for the backplane.

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jayjay1974 wrote:
just plenty of outputs, one for each segment and one for the backplane.

I doubt you meet 25uA requirements with that as the glass needs to be refreshed over 30 times per second (not mentioning the contrast problem). The chips with a built-in hardware LCD driver +RTC consume 25uA @ 1.8V and that seems to be the lower bound. But I have never tried bit-banged LCD and power consumption...

No RSTDISBL, no fun!

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Yes, dedicated LCD drivers are likely more optimized for power consumption; after all it's only an array of XOR ports (for static drive) while an AVR has to do a lot more to achieve the same.

I once did controlled a static LCD with 5V GALs. No contrast problems but don't even think of asking me about power consumption :)

Of course the OP could also buy a 50 cent LCD clock.

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Quote:

The chips with a built-in hardware LCD driver +RTC consume 25uA @ 1.8V and that seems to be the lower bound.

Hmmm--interesting. I've got '169-family LCD apps, but never was in search of absolute lowest power consumption on those apps. I assumed it would be power-efficient, I guess.

I've got an indoor-outdoor thermometer on my kitchen wall, with 2x 7-seg 4+ digit LCD displays. It has been going continuously for well over 10 years on the original button cell.

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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Quote:

The chips with a built-in hardware LCD driver +RTC consume 25uA @ 1.8V and that seems to be the lower bound.

I had to take a peek at the datasheet. The 25uA is active mode at 32kHz. But, let's remember that OP wants to make an LCD clock drawing that amount--32kHz for timekeeping; job done. ;)

Now, there are indeed a number of LCD refresh interrupts each second, IIRC. Why can't you go to one of the supported sleep modes between? I'd think that would cut down the consumption.

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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theusch wrote:
The 25uA is active mode at 32kHz.

You are right, this is an active mode!
I didn't find any information about how much current LCD controller draws, but:

    - We can assume the currents are additive, so - 25uA(LCD+32kHz active)-8uA(32kHz active)=17uA(only LCD), and
    - 0,6uA(RTC+power-save)+17uA(only LCD)=17,6uA(RTC+LCD+power-save).
But I am not sure if LCD can run with 1.8V power supply or what capacitances the driver charges.

Still 25uA is a challenge with a dedicated LCD driver it seems(BOD, watchdog, computations and such), cpu has to wake up every second. With a bit-banging you need to wake up CPU at least 30 times per second(this must start the clock initially as it takes some time, even with RC)..

But on the other hand you could use just any AVR_P with 33 IOs +RTC (I think you will not find many of them, as those in TQFP44 have about 32 IOs). So you must pick something with at least 35 IOs and with P at the end.. Not including push-buttons for setting the time. Any propositions?
Bit-banged ATMega169P?

No RSTDISBL, no fun!

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Quote:

Any propositions?

Proposition 1: 25uA is arbitrary. Just about any old coin cell would give 1-year+. Is OP making 1 or 1000 or 100000? At the low end, who cares (about the last few Ua).

Proposition 2: Take a Butterfly , put it in clock mode, and poke at it to get some numbers. (Remember that is probably a '169 and a PA would probably do better.) BTW: Project done after purchasing the Butterfly.

Proposition 3: The choice of static/single-common is probably as arbitrary as the 25uA.

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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You are right. It all depends on the quantities involved. And there are so many varieties of clocks and watches, I do not think this is a niche where you could place your business :(

I agree - AVR Butterfly is perfect for the start with LCD glasses, although it is not that P!

No RSTDISBL, no fun!

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This is a 15 micro-watt (static, typical) or 50 micro-watt (1Hz, typical) graphics LCD (144x168, 0.145mm pitch):
http://www.sharpmemorylcd.com/1-26-inch-memory-lcd.html
5v power, 3v or 5v inputs, SPI interface, 1Hz inversion signal.

"Dare to be naïve." - Buckminster Fuller

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What MCU do you recommend for a software lcd driver?
PS, it's just for me, not for sale...

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Quote:

What MCU do you recommend for a software lcd driver?
PS, it's just for me, not for sale...


I recommend getting an AVRButterfly. ATAVRBFLY. DigiKey has 1000 of them at $21.
http://search.digikey.com/script...

Now you will have the LCD, the AVR that drives it, schematics, lots of discussions here, and lots of code available to start with.

You can then learn to your heart's content. If, when you have mastered it, you feel you can do better then you can plan your own processor-LCD combination. [Hint: I'd predict that even if you are an experienced circuit-board person, you will face some challenges. As the LCD is such low power, just traces of stray capacitance will give you less than ideal results.]

See also
http://www.smileymicros.com/inde...
http://www.smileymicros.com/inde...
which has a section on LCD programming.

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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My first bet would also be on the Butterfly to start with.

But I wouldn't write of TI on first hand. I especially like their watch, the EZ430-chronos which is an amazing and inspiring development kit for it's $50.

http://processors.wiki.ti.com/in...

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

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But what about your requirements? You asked about 25uA current and a not muxed LCD driver IIRC. Does this kit meet your criteria? It has a 96 segment LCD so I doubt it has 97 IO pins for driving its LCD..

No RSTDISBL, no fun!