Ender 3 Display Task Timer

ST7920 ENH12864Z-1 + Arduino Uno

A standalone task timer using the Creality Ender 3 display (ENH12864Z-1) wired to an Arduino Uno via the EXP3 connector.

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Photos

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Hardware

• Display: Creality ENH12864Z-1 (ST7920, 128×64 monochrome LCD)
• Microcontroller: Arduino Uno (USB 5V powered)
• Library: U8g2 (install via Arduino Library Manager)

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Display Connector Overview

The ENH12864Z-1 has three connectors on the back:

Connector	Purpose
EXP1	Parallel LCD data + encoder click + buzzer
EXP2	SPI + SD card + encoder rotation
EXP3	Combined single-cable SPI interface (used in this project)

EXP3 is used for this project — it combines all needed signals into one connector, reducing wiring from 13 wires down to 9.

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EXP3 Pinout

EXP3 is a 2×5 (10-pin) 2.54mm pitch IDC connector.

    NOTCH
  ┌───────┐
  │ 2  1  │  ← Pin 1 marked with dot/triangle on PCB
  │ 4  3  │
  │ 6  5  │
  │ 8  7  │
  │ 10  9 │
  └───────┘
  Odd  = right column
  Even = left column

Pin	Signal	Wire Color	Description
1	GND	Black	Ground
2	CS	Grey	SPI Chip Select
3	Knob Rotation 1	Yellow	Encoder channel A
4	Knob Rotation 2	Orange	Encoder channel B
5	Beeper	Red	Buzzer signal
6	—	—	Not used
7	5V	Brown	Power
8	Data (MOSI)	Blue	SPI data
9	Clock (SCK)	Green	SPI clock
10	Knob Button	Purple	Encoder push button

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Wiring — EXP3 to Arduino Uno

EXP3 Pin	Signal	Wire Color	Arduino Uno Pin
1	GND	Black	GND
2	Chip Select	Grey	D10
3	Knob Rotation 1	Yellow	D2
4	Knob Rotation 2	Orange	D3
5	Beeper	Red	D5
7	5V	Brown	5V
8	Data (MOSI)	Blue	D11
9	Clock (SCK)	Green	D13
10	Knob Button	Purple	D4

Note: Pin 6 is not connected. Only 9 of the 10 pins are used.

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Power

The Arduino Uno is powered via USB (5V). The display draws approximately:

Component	Current Draw
ST7920 LCD	~20mA
Backlight	~40mA
Buzzer (peak)	~30mA
Encoder	~5mA
Arduino Uno	~50mA
Total	~145mA

A standard USB port provides 500mA — well within limits.

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Wiring Notes

• All connectors are 2.54mm pitch (standard Dupont spacing)
• Use female-to-female Dupont jumper wires to connect individual EXP3 pins to Arduino headers
• Alternatively, use a 10-pin IDC to Dupont breakout cable for a cleaner connection
• Pin 1 on EXP3 is marked with a dot or triangle on the PCB
• The connector has a keying notch — ensure ribbon cables are inserted in the correct orientation

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Connector Identification — How to Find Pin 1

1. Look at the back of the display PCB
2. Find the small triangle (▲) or dot (•) printed next to one corner of the connector
3. That corner is Pin 1
4. Pins are numbered with odd numbers on the right and even numbers on the left, counting down from the top

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Software Setup

1. Install Arduino IDE
2. Open Library Manager (Tools → Manage Libraries)
3. Search for U8g2 and install
4. Open task_timer.ino
5. Select Board: Arduino Uno and correct COM port
6. Upload

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Timer Operation

State	Action	Input
Setting	Turn encoder to adjust time	Rotate knob (5 min increments)
Setting	Start timer	Click knob
Running	Pause timer	Click knob
Paused	Resume timer	Short click
Paused	Reset to setting	Hold knob 1 second
Done	Set new timer	Click knob

The default time is 45 minutes. The display shows a progress bar while the timer is running. The buzzer beeps 3 times when the timer reaches zero.

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Pin Summary (Arduino Uno)

Arduino Pin	Function
5V	Display power
GND	Ground (shared)
D2	Encoder A (interrupt)
D3	Encoder B (interrupt)
D4	Encoder button
D5	Buzzer
D10	SPI Chip Select
D11	SPI MOSI (data)
D13	SPI SCK (clock)

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Files

File	Description
task_timer/task_timer.ino	Arduino sketch
ender-front.jpg	Display front view
ender-back.jpg	Display back view (connectors)
README.md	This file