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Comment by andmarios | Hacker News Reader

This. Or Attiny85 with external programmer and then read the microcontroller's datasheet to see how you can enable various sleep modes.

The attiny85 can get to μA while sleeping.

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There aren't enough IO pins on an Attiny85 to measure the temperature and send it to another device wirelessly, right ?

There are - two for power, two for the DHT sensor, two for RX TX, and you even have one left over (not counting reset pin)

I'm using serial from ATTiny85 to a ESP8266 as my wireless transmitter already: https://i.imgur.com/vZzGGZL.png but the ESP itself is probably the root of the power problem.

It has 6 pins you can use which should be more than enough.

Once I had two DS18B20 sensors (temp), one 1602 LCD (over I2C) and a PIR sensor to act as interrupt connected to a attiny85. One temp sensor shared the same pin with the I2C data line. I just had to make sure they weren't used at the same time.

This setup let me with two pins free, one of which I used as sink (ground) for the LCD, thus effectively being able to turn it off by pulling up the pin.

There are enough pins, the actual reason I didn't go with the Attiny85 is because of the Arduino libraries I'm using.

I think they needed an extra timer that the attiny85 didn't have.

Attiny84 wasn't exactly plug and play either, as I had to adapt the Arduino libraries code to it, but at least all the hardware was there.

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