Hello I'm looking for the smallest and low power micro processor that i can program using arduino ide. I only need 1 or 2 pins to blink lights and a button push. Does anyone know a processor like that? I can do it with a attiny85 or 85 But they take a lot of power. This is for a gift I'm building for my wife and they need to take 1 or 2 coin cell batteries. Doesn't need to stay on long.
Joseph
Some comparisons
Possibly change the attiny85 to 8Mhz and sleep between any actions?
An ATTINY85 in deep sleep mode will last for months on a coin cell!
Post the sketch you prototyped and perhaps we can come up with a solution for you. 
Hello chrisknightley, Thank you i have never heard of the attiny 10,9 or 8 one before. That is new to me. I'm looking into it now.
Joseph
I didn't know there was a sleep mode fot the attiny85. I will look into that as well. Thank you.
Joseph
missdrew said that as well I'm going to look into it thank you.
Joseph
Take a look at the datasheet ..........................
As long as you use sleep mode well, most uCs can work with coin cells for months.
(Of course, Excluding other current consumption factors.)
In other words...
Perhaps you should choose according to the physical-package-size of uC you want to use.
The rest is code.
Me and datasheets got a Well lets just say not so good together hehe. But i will give it a look. Thank you
Joseph
I'm looking just for a few hours the mostly. If it last longer then that /i'm okay with that.
Joseph
Define smallest? Smallest physical size?
Yes the size of the micro processor not the amount of what it can do. Sense I’m not using lcds or sensors I’m just blinking some leds. It also doesn’t need much sketch space.
Joseph
Physical size is determined by the packaging of the die, so the same microcontroller can have different physical sizes. Several microcontrollers in the tinyAVR 0-series and tinyAVR 1-series can be bought in a 3x3mm QFN package. Is that small enough? While it's possible to find microcontrollers that are smaller, It might be difficult finding ones that are supported by the Arduino framework.
The ATtiny1606 has a 20pin 3x3mm package: https://www.microchip.com/en-us/product/ATTINY1606
Soldering is another issue though. You will not be able to solder this IC with a soldering iron.
The smallest I have used is the ATtiny84 in the VQFN package. 3mmx3mmx0.8mm 20 pin of which only 14 are connected. It is probably the same as the above 1606 package. I use a hotplate to reflow solder them.
The datasheet calls it the 20M2 package.
EDIT: For programming the 1606 is probably a better bet since it uses a single UPDI pin for programming. The 84 will need SPI (4 pins).
Willem.
The smallest size I have enough pins is up to 5 pins on each size through hole is okay but i can solder pretty much anything even if it is surface mount I can do.
Edit: the attiny10 I looked into they will do the job. Thank you all for the help. I looked into 20 different processors.
Joseph
The ATtiny4/5/9/10 in the 6ST1 (SOT23?) package is 2.8 to 3.0 mm long and 2.6 to 3.0 mm wide across the leads. You could straighten the leads or tuck them under to reduce the width a bit but it would probably still be wider than 2.0 mm.
In the 8MA4 package (pads on the bottom instead of leads) it is 2.05x2.05 or smaller. That would make it the smaller package. Not to mention that the 6ST1 is about two and a half times as tall (1.45 vs 0.6 mm).
QFN can be soldered just fine with a 1mm tip. It's not as hard is it might seem, as odd as it may sound. I haven't had all that much trouble soldering 24-pad 0.5mm pitch WQFN's.
Well what do you do with the exposed pad? It's typically part of the thermal design of the IC, so if it's not soldered I wouldn't consider it soldered properly.
That said, you might be able to get it to run code, though I wouldn't personally bother when hot air soldering is so much easier (in my opinion).
