Taking arduino circuit and making it a small dedicated project

Projects General Guidance
1

I am working on a simple pulse counter for electricty monitoring in my home.

My device/circuit will/does contain the following

  • Serial Bluetooth Module - bought off www.dealextreme.com for $6.60 USD
  • Schmitt Trigger - 40106
  • Light Dependant Resister
  • Possibly a Real Time Clock - Not sure if I need it yet - may just use the PC clock when saving data.
  • Arduino Duemilanova

I want to make the hardware small (not SMD but small) - low power and self contained so I want to remove the Arduino itself and use something smaller, but something that still works with Arduino code.

So my question is how to shrink this down?

Could I look at an ATTINY85? I think this does not have a UART so my TX/RX is a problem on the Bluetooth Module - Am I correct? - I found this video

Could I look at a simple ATMega 168 or similar as seen in this video

I am currently needing 3.3v and 5v but that could be reduced to the 3.3v alone ( the schmitt trigger is a 40106 which can run at 3v - currently 5)

I need one digital input which triggers an interrupt when it changes.

If anyone has any ideas I would really appreciate them

Cheers

chris

2

The serial port on the ATTiny85 can be used as a UART but only in half-duplex mode. Any incoming received data will garble the data being transmitted, because the same register is used for both transmit and receive. If you need full duplex, then one possibility is to use the serial port to receive data, but transmit data using a software UART. Either way, you will either need to use a crystal or ceramic resonator, or you will need to calibrate the internal clock in order to achieve sufficient frequency accuracy.

What are you using the Schmitt trigger for? There may be alternative solutions that avoid it, for example using an analog input instead, or connecting the pin directly to the input (the input pins have internal Schmitt triggers with about 200mV of hysteresis).