This week I had two ATTiny84s talk to each other using my input and output devices.
One ATTiny84 was hooked to a led and potentiometer (and motor). The other other was hooked to a led and button.
The ATTiny84 with the pot was programmed to send the signal to port PA0, which was serially interfaced to the second ATTiny84.
The second ATTiny84 responded by blinking the LED (or changing the motor speed).
My next step is to have a button from the second ATTiny84 trigger the motor speeds on the first ATTiny84. This week was buildng on the Input Devices, Output Devices, and Interface week so it felt pretty straightforward.