Bill of Materials

• M2 bolts - 10 mm (4 quantity)
• M2 nuts (4 quantity)
• 3D printed case (2 pieces)
• 1.3” IPS TFT (generic version used here, 7789 chipset)

• Adafruit Itsy Bitsy M4 Express (https://www.adafruit.com/product/3800)
• Adafruit DS3231 breakout (https://www.adafruit.com/product/3013)
• CR1220 Battery (https://www.adafruit.com/product/380)

Wiring Instructions

The following table shows the wiring instructions for the Itsy Bitsy, the TFT display and the DS3231 real-time clock breakout.  The wiring color indicates the wire insulation color that is shown in the images.

Special notes on the software (Arduino)

Be sure to include the images.h file into your Arduino project.

The generic IPS TFT display I used has a ST7789 chip, and it required to use "SPI_MODE3" in the tft.init statement.

I control the backlight brightness by a PWM signal.  I selected a value of 8 since this is a bedside clock.  Also, you can change the minute hand to a different color.  White can be very bright at full brightness (255).

I updated the software to includes the hooks for daylight savings time using the Timezone library (https://github.com/JChristensen/Timezone).  Before compiling, update the Timezone rules for your location.

Also, I am including a short program to update the real-time clock to the current time.  Run this to update the RTC before you load the final program.  This short code allows you to update the real-time clock to UTC time by providing a few variables so you can create the correct time offsets.  

3D Printing the case

The case is relatively easy to print.  I printed the front standing upright, with support.  I printed the back piece with the back lying flat on the print bed.