The Nokia 3120 Keypad SMS Sender has been updated to v1.1 to use the ATtiny261 and another ULN darlington array. View the project page.
v1.1 (29 January 2012) – Download
- Uses ATtiny261 to remove the extra transistor / mosfet circuit
- Uses a ULN2003A instead of 4 transistors
- Use a spare output on a ULN2003A to turn the phone on when we want to send an SMS
therefore saving the battery until we need it
- Use the watchdog timer instead of delay_ms