RM68120 TFT Display: Setup and Configuration Guide

The RM68120 is a high-density single-chip TFT driver manufactured by Raydium Semiconductor Corporation, targeting WVGA-class portable displays in smartphones, PMPs, and other compact devices. It supports resolutions from 480 RGB × 360 up to 480 RGB × 864 dots with an internal GRAM and delivers 16.7 million colours — a significant step up from the 262K-colour controllers common in the TFT_eSPI ecosystem. The library includes driver configuration files for the RM68120, making it straightforward to attempt integration, though caution is warranted given the current testing status.

Support files for the RM68120 have been added to TFT_eSPI, but the driver is untested. Hardware verification has not been confirmed by the library maintainer. Proceed with the expectation that you may need to troubleshoot initialisation sequences or register settings before achieving a working display. Community feedback and pull requests with verified configurations are welcome.

Controller Overview

The RM68120 is a SoC driver for a-Si TFT LCD panels integrating a 1440-channel source driver, gate-control timing via level shift, 1,244,160 bytes of on-chip GRAM (for the 480 × 864 configuration), and a complete power supply circuit. It is designed around a 1.65 V I/O interface voltage with an internal voltage follower generating all required LCD drive rails. The controller’s support for SPI, parallel MCU bus, I²C, RGB video, MDDI, and MIPI DSI interfaces makes it one of the most versatile controllers in the library’s supported list, though TFT_eSPI exercises only the SPI and parallel MCU paths.

Key Specifications

Parameter	Value
Maximum resolution	480 RGB × 864 dots (with GRAM)
Bypass-GRAM resolution	480 RGB × 1024 dots
On-chip GRAM	480 × 3 × 864 = 1,244,160 bytes
Colour depth	16.7M (24-bit), 262K (18-bit), 65K (16-bit), 8-colour idle
Source driver channels	1,440
System interfaces	8/16/24-bit 80-series MCU, 16-bit SPI, I²C
Video interfaces	16/18/24-bit RGB (SYNC and DE mode)
High-speed interfaces	MDDI V1.2, MIPI DSI V1.01
I/O supply (IOVCC)	1.65 V – 3.3 V
Low-swing I/O (IOVCCL)	1.1 V – 1.3 V
Operating temperature	−30 °C to +70 °C

Supported Resolutions

The RM68120 can be configured for several display panel sizes, all sharing the 480-pixel horizontal dimension:

With GRAM
Bypass GRAM

Option	Resolution
1	480 RGB × 360
2	480 RGB × 640
3	480 RGB × 720
4	480 RGB × 800
5	480 RGB × 854
6	480 RGB × 864

Option	Resolution
1	480 RGB × 1024

Bypass-GRAM mode streams pixel data directly from the host without storing it in the on-chip frame buffer — useful for hosts with sufficient RAM and high-bandwidth interfaces.

Interface Options

Parallel MCU Bus

8-bit, 16-bit, or 24-bit 80-series (Intel) parallel interface. Highest throughput option when GPIO count permits.

SPI (16-bit)

16-bit serial peripheral interface. Lower pin count at the expense of raw fill rate.

I²C

Low-pin-count bus, typically used for configuration commands rather than pixel data.

RGB Video

16/18/24-bit RGB interface with SYNC or DE mode for framebuffer-driven SoCs.

TFT_eSPI targets the parallel MCU bus and SPI paths. The RGB, MDDI, and MIPI DSI interfaces are outside the library’s scope.

Configuration

Select the RM68120 driver

Open User_Setup.h and enable the RM68120 driver. Disable all other driver definitions:

#define RM68120_DRIVER

Set display dimensions

Choose the vertical resolution to match your specific panel. The most common WVGA variant is 480 × 800:

#define TFT_WIDTH  480
#define TFT_HEIGHT 800   // Adjust to match your panel: 360, 640, 720, 800, 854, or 864

Define pin assignments (SPI example, ESP32)

#define TFT_MOSI 23
#define TFT_SCLK 18
#define TFT_CS   15
#define TFT_DC    2
#define TFT_RST   4
#define TFT_MISO 19   // Optional

Set SPI frequency

Start conservatively with a lower clock speed when first testing an untested display configuration:

#define SPI_FREQUENCY      20000000   // 20 MHz — safe starting point
// #define SPI_FREQUENCY   27000000   // Increase once basic display works
#define SPI_READ_FREQUENCY 20000000

Complete User_Setup.h Example (ESP32 SPI, 480×800)

// ---- Driver selection -----------------------------------------------
#define RM68120_DRIVER

// ---- Display dimensions ---------------------------------------------
#define TFT_WIDTH  480
#define TFT_HEIGHT 800

// ---- Pin definitions (ESP32 VSPI) -----------------------------------
#define TFT_MOSI 23
#define TFT_SCLK 18
#define TFT_CS   15
#define TFT_DC    2
#define TFT_RST   4
#define TFT_MISO 19

// ---- SPI clock frequencies ------------------------------------------
#define SPI_FREQUENCY      20000000
#define SPI_READ_FREQUENCY 20000000

// ---- Fonts (optional) -----------------------------------------------
// #define LOAD_GLCD
// #define LOAD_FONT2
// #define LOAD_FONT4
// #define SMOOTH_FONT

Power Supply Architecture

The RM68120 incorporates an on-module DC/DC converter that generates all LCD drive voltages from the VCI input. The output rails and their typical operating ranges are:

Rail	Range	Function
DDVDH	+4.5 V to +6.5 V	Positive source driver supply
DDVDL	−4.5 V to −6.5 V	Negative source driver supply
VCL	−2.5 V to −4.0 V	Negative LCD drive
VGMP	+3.5 V to +5.0 V	Positive gamma high voltage
VGSP	0.0 V, +0.3 V to +3.7 V	Positive gamma low voltage
VGMN	−5.0 V to −3.5 V	Negative gamma high voltage
VGSN	0.0 V, −0.3 V to −3.7 V	Negative gamma low voltage
VGH	+8 V to +18 V	Gate-on drive voltage
VGL	−2 V to −15 V	Gate-off drive voltage
VCOM	−3.5 V to 0 V	Common electrode VCOM

Power-Saving Modes

The RM68120 provides three hardware-controlled power saving modes:

Mode	Description
Deep Standby	All internal circuits off. Lowest power state.
Sleep Mode	Controller halted, GRAM retained. Fast wake-up available.
8-Color Idle	Reduced to 8-colour display to cut power while remaining visible.

Display Quality Features

The RM68120 includes several hardware features that improve display quality without CPU involvement:

Programmable γ-correction — individual gamma curves for each of the R, G, and B channels for the full 16.7M colour mode.
Inversion modes — supports 1-dot, 2-dot, 3-dot, 4-dot, column, and zigzag inversion to eliminate flicker.
Partial display function — a rectangular window area of the GRAM can be refreshed independently of the rest of the screen.
Window address function — limits GRAM writes to a defined rectangular region, enabling efficient sprite and region updates.
On-chip checksum — hardware checksumming of GRAM contents to detect data corruption.
Four GPO pins — general-purpose output pins for external control (e.g., backlight, reset of peripheral ICs).
Power supply startup sequencer — automatic power-on sequencing removes the need for host-side delay loops during initialisation.

Basic Usage

#include <TFT_eSPI.h>

TFT_eSPI tft = TFT_eSPI();

void setup() {
  tft.init();
  tft.setRotation(0);          // Portrait: 480 wide × 800 tall
  tft.fillScreen(TFT_BLACK);

  tft.setTextColor(TFT_YELLOW, TFT_BLACK);
  tft.setTextFont(4);
  tft.drawString("RM68120 Init OK", 20, 20);
}

void loop() {
  // Simple colour sweep to verify display operation
  tft.fillScreen(TFT_RED);   delay(500);
  tft.fillScreen(TFT_GREEN); delay(500);
  tft.fillScreen(TFT_BLUE);  delay(500);
}

When bringing up an untested display for the first time, start with tft.fillScreen() calls using primary colours (red, green, blue) to confirm pixel output is working before attempting text or graphics. A solid red, green, or blue screen rules out wiring and power supply problems quickly.

Datasheet Reference

The full RM68120 datasheet, including register definitions and initialisation sequences, is available at:

https://www.displayfuture.com/Display/datasheet/controller/RM68120.pdf

Getting Started

Core Concepts

Drawing & Graphics

Advanced Topics

Hardware

Examples

RM68120 TFT Display: Setup and Configuration Guide

Controller Overview

Key Specifications

Supported Resolutions

Interface Options

Parallel MCU Bus

SPI (16-bit)

I²C

RGB Video

Configuration

Complete User_Setup.h Example (ESP32 SPI, 480×800)

Power Supply Architecture

Power-Saving Modes

Display Quality Features

Basic Usage

Datasheet Reference

Build docs developers (and LLMs) love

Getting Started

Core Concepts

Drawing & Graphics

Advanced Topics

Hardware

Examples

Documentation Index

​Controller Overview

​Key Specifications

​Supported Resolutions

​Interface Options

Parallel MCU Bus

SPI (16-bit)

I²C

RGB Video

​Configuration

​Complete User_Setup.h Example (ESP32 SPI, 480×800)

​Power Supply Architecture

​Power-Saving Modes

​Display Quality Features

​Basic Usage

​Datasheet Reference

Build docs developers (and LLMs) love

Controller Overview

Key Specifications

Supported Resolutions

Interface Options

Configuration

Complete User_Setup.h Example (ESP32 SPI, 480×800)

Power Supply Architecture

Power-Saving Modes

Display Quality Features

Basic Usage

Datasheet Reference