RTC on the ATtiny1614

Use the built-in RTC/PIT functionality for clock/alarm functionality. Avoid external RTC chips/modules.

Background reading

• ATtiny1614 datasheet
• Technical Brief (TB) 3213
• megaTinyCore

Arduino setup

ATtiny1614 running with 20 MHz internal RC oscillator and 12.5pF 32.768Khz watch crystal, programmed using megaTinyCore:

Flashed using UPDI.

Alarm circuit (post flash)

• Baseline power consumption: 1.3uA
• Serial mode entered via DTR/RTS signal on serial monitor connect, power consumption: 1.6mA
• LED consumption at V_cc 4.5V, forward voltage 2.9V: 20mA
• Date, time and alarm programmed over serial (9600 baud)
• Pullup on R_x/T_x to prevent garbage on connect