In a recent instructable Indigod0g described a mini weather station that works pretty well, using two Arduinos. Maybe not everyone wants to sacrifice 2 Arduinos to get humidity and temperature readings and I commented that it should be possible to do a similar function with two Attiny85’s. I guess talk is easy, so I better put my money where my mouth is.
In fact, if I combine two earlier instructables I wrote:
2-Wire LCD interface for Arduino or Attiny
Receiving and sending data between Attiny85 (Arduino IDE 1.06)
then most of the work is already done. Only need to adapt the software a bit.
I chose for a two wire lcd solution with a shift register, rather than an I2C LCD because on the Attiny the shift register is easier to implement than the I2C bus. However… if you for instance want to read a BMP180 or BMP085 pressure sensor, you need I2C for that anyway so you might as well use an I2C LCD then too. TinyWireM is a good library for I2C on an Attiny (but it requires extra space).
10 k resistor
433MHz transmitter module
433 MHz receiver module
74LS164 shift register
1x1k variable resistor
an LCD display 2x16The transmitter is a very basic configuration of the Attiny85 with a pull up resistor on the reset line.
A transmitter module is attached to digital pin ‘0’ and the DHT11 data pin attaches to digital pin 4.
Attach a wire of 17.2 cm as antenna (for a much better antenna see step 5).
For more detail: Mini weather station with Attiny85