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obvious clock is obvious

It's a simple digital clock with bright numbers and wires. It looks like a clock. What else would it look like?

douglas-henkeDouglas Henke
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This is a simple clock I threw together from parts (and software libraries) I had on hand. The design is pretty much the most obvious cliche thing you would think of if someone told you "microcontroller-based digital clock".

The only surprises, if there have to be some, are 1) the use of a rotary encoder as the the sole input device and 2) the use of 14-segment LEDs instead of 7-segment.

This is marked "ongoing project" because I have plans to add an RDA5807 FM radio module, put it in a nice case, and use it as a clock radio to get up in the morning.

On the "maybe someday" list of features: replace the ATTiny85 with an ESP8266 and have it sync to the NTP server on my local network.

This is a pretty basic microcontroller-based clock.

An ATTiny85 (on an Adafruit Trinket board) runs everything.

There is a Dallas Systems DS1307 real-time clock module that keeps track of the time. It has its own crystal and battery. It talks to the CPU over I2C.

The sole user input is the rotary controller. You can turn it left or right, or push it down. I use it to implement a simple menu system where right=next, left=previous, press=OK and long press=back/cancel. It is connected to the CPU on three input lines (two for quadrature and one for the button). Debouncing is done in software.

The display is also run over the I2C bus.

  • 1 × Adafruit Trinket 3.3V proto board based on ATTiny85
  • 1 × DS1307 RTC breakout board I2C real-time clock with local oscillator and battery
  • 1 × Adafruit 14-segment x 4 LED backpack I2C display module with nice constant-current drivers
  • 1 × PEC11-4215F-S24 rotary encoder quadrature encoder with detents and pushbutton
  • 1 × breadboard Electronic Components / Misc. Electronic Components

View all 7 components

  • Update Source Tarball Adds Missing BSD License

    Douglas Henke • 09/23/2015 at 21:30 • 0 comments

    The first source tarball I linked to had some junk files that should have been deleted, and was missing the COPYING file giving the (3-clause BSD) license. I've linked to an updated tarball, but left the old link (clearly labeled) in place.

    No functional changes, just fixing a dumb mistake. Obvious error is obvious (in hindsight).

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