12864B Graphic LCD Module - 128x64 Pixels, Yellow-Green Backlight, ST7920

Specifications

• Display Format: 128 x 64 Dots (Graphic)

• Controller IC: ST7920 (or equivalent compatible)

• Backlight Color: Yellow-Green (LED)

• Pixel Color: Dark Blue/Black

• Operating Voltage (VDD): 5V DC

• Logic Voltage: 5V (3.3V compatible on some data pins, but 5V power required)

• Communication Interfaces: 8-Bit/4-Bit Parallel OR 3-Wire Serial (SPI)

• Contrast Adjustment: Required (via external 10K potentiometer on Vo pin)

• Pin Count: 20 Pins (Standard 2.54mm pitch)

• Module Dimensions: ~93mm (L) x 70mm (W) x 13mm (H)

• Viewing Area: ~72mm x 40mm

Downloads:

• Arduino Library: U8G2 by Olikraus. This is the most advanced and popular library, and it supports all graphics functions too.
• ST7920_Datasheet

Key Applications and Projects

• 3D Printer "Smart Controllers": This is the exact screen panel used in the famous "RepRap Full Graphic Smart Controller" to display temperatures and print coordinates.

• Custom Synthesizers: Building a retro MIDI interface with graphical envelope curves and waveform readouts.

• Weather Stations: Plotting a 24-hour barometric pressure history graph alongside large, bold temperature readouts.

Unlock New Capabilities (Project Evolution) The Interactive CNC Control Pendant: Stop running back to your laptop every time you need to jog your CNC router! Evolve your workshop! Mount this 12864B screen inside a handheld plastic enclosure alongside a rotary encoder knob and an emergency stop button. Wire it to your GRBL controller. Using the U8g2 library, you can program a deeply nested graphic menu system to jog axes, set work zeroes, and monitor spindle speeds directly from the palm of your hand, giving your DIY machine true industrial-level operability!

PACKAGE INCLUDED

• 1 x 12864B Graphic LCD Module (Yellow-Green)

FREQUENTLY ASKED QUESTIONS (FAQ)

1. What does "12864" mean? It refers to the screen's graphic resolution: 128 pixels wide by 64 pixels tall.

2. Can this display colors? No, this is a monochrome (single-color) LCD. It can only display dark pixels against the illuminated yellow-green background.

3. What is the ST7920 chip? It is the microprocessor built into the back of the LCD module. It receives commands from your Arduino and translates them into the electrical signals needed to turn individual pixels on and off.

4. Why is the screen completely blank when I turn it on? You must wire a 10K ohm potentiometer to pin 3 (Vo or Contrast). If the contrast is not tuned perfectly, the pixels will remain invisible, even if your code is running perfectly.

5. How do I wire the contrast potentiometer? Connect one outer leg of the 10K potentiometer to 5V, the other outer leg to Ground (GND), and the middle "wiper" leg to pin 3 (Vo) on the LCD. Turn the knob until the graphics appear clearly.

6. What is the PSB pin (Pin 15) for? PSB stands for Parallel/Serial Bus selection.

• Connect PSB to 5V (HIGH) to use 8-bit Parallel mode (requires ~10 pins).

• Connect PSB to GND (LOW) to use SPI Serial mode (requires only 3 pins).

7. How do I wire it for SPI mode on an Arduino? Wire PSB to GND. Then connect RS (Chip Select) to Arduino Pin 10, R/W (MOSI/Data) to Pin 11, and E (SCK/Clock) to Pin 13. (These pins can vary based on your specific code definition).

8. Can I use this with a 3.3V board like an ESP32? The main power (VDD) usually requires 5V to drive the LCD fluid properly. However, the ST7920 logic pins can often recognize 3.3V data signals from an ESP32 if wired in SPI mode. For ultimate reliability, use a 5V logic level converter.

9. Why are Pins 19 (BLA) and 20 (BLK) separate from VDD and GND? Pins 1 and 2 power the logic chip. Pins 19 (Backlight Anode) and 20 (Backlight Cathode) power the yellow-green LEDs. You should put a small resistor (e.g., 220 Ohm) in series with Pin 19 to prevent the LEDs from burning out, though many modern boards have a built-in current-limiting resistor on the back.

10. What Arduino library should I use? The U8g2 library by Olikraus is the absolute best library for this display. It is incredibly fast and includes hundreds of custom fonts and shape-drawing commands.

11. My text is printing backwards or mirrored. How do I fix this? Some generic ST7920 boards have their hardware origin mapped backward. In the U8g2 library, you simply change your initialization constructor (e.g., changing U8G2_R0 to U8G2_R2) to flip the screen via software.

12. Can this display standard text without a graphics library? Yes. The ST7920 has a built-in character ROM for basic Latin and Chinese fonts, but using a graphics library like U8g2 is much more flexible and preferred by most makers.

13. Does this screen suffer from "burn-in"? No, LCDs do not suffer from permanent burn-in like OLEDs do. You can leave a static image on this screen for years without damaging it.

14. What is the viewing angle like? Like most standard STN monochrome displays, the viewing angle is optimized for looking straight on or slightly from below (the 6 o'clock viewing direction). Contrast will degrade if viewed from sharp side angles.

15. How much power does it draw? The logic chip draws very little power (a few mA), but the yellow-green LED backlight can draw between 50mA to 100mA depending on brightness.

16. Can I adjust the backlight brightness? Yes. Instead of wiring Pin 19 (BLA) directly to 5V, you can wire it to a PWM-capable pin on your Arduino. By writing an analog value (0-255), you can smoothly dim the backlight.

17. What are the VEE (Pin 18) and NC (Pin 16) pins? NC stands for No Connection. Leave it empty. VEE outputs a negative voltage generated by the LCD, which was used for contrast tuning on older revisions. On most modern ST7920 boards, you can ignore VEE and tune contrast using Vo to Ground.

18. Why does the screen refresh look slow or "ghosty"? Monochrome LCD fluid has a slow response time compared to modern TFTs. Rapidly moving animations will leave a slight ghosting trail, which is an inherent physical property of this technology.

19. Are the header pins pre-soldered? Usually, this module ships with the 20-pin male header row already soldered into the bottom of the board, allowing you to plug it directly into a large breadboard.

20. Will this work as a direct replacement for my broken 3D printer screen? If your 3D printer uses the standard "RepRap Discount Full Graphic Smart Controller," this is the exact raw LCD panel inside it. However, you will need to desolder the old one from the adapter board and solder this one in its place.