**1 Introduction**
Organic Light-Emitting Diode (OLED) displays have become a promising alternative to traditional Liquid Crystal Displays (LCDs), offering several advantages that make them more suitable for modern applications. Unlike LCDs, which require a backlight and suffer from limited viewing angles, OLEDs emit light on their own, allowing for a wider viewing angle of up to 170°. They are also lighter, thinner, and capable of higher brightness and luminous efficiency. With a fast response time—up to 1000 times faster than LCDs—OLEDs provide superior dynamic image quality. Additionally, they operate effectively across a wide temperature range, from -40°C to 80°C, and consume less power while being more resistant to shocks. These features make OLEDs ideal for use in high-brightness instruments and military-grade devices. Although OLED technology is still in its early stages compared to the well-established LCD market, its growing potential suggests it may soon replace LCDs in many applications. The industry widely recognizes OLEDs as the next generation of display technology due to their versatility and performance.
**2 Hardware Structure Design**
This paper presents a design that uses the C8051F023 microcontroller as the core control unit for a 128×64 monochrome OLED display. The OLED module used is VGG12864G, which is driven by the Solomon SSD1303 IC. This system supports both text and image display, either static or dynamic. The overall hardware block diagram is illustrated in Figure 1.
**2.1 SSD1303 Driver and Interface Circuit**
The VGG12864G module features 128 columns and 64 rows. The SSD1303 driver IC is responsible for controlling the OLED panel. As shown in Figure 2, the SSD1303 includes row and column drivers, an oscillator, contrast controller, and graphics data RAM (GDDRAM). This integration reduces the need for external components and lowers power consumption. The driver supports a maximum resolution of 132×64, with the bottom 132×16 area capable of displaying four colors. It can also be programmed for 64 gray levels or 256 contrast levels when used for monochrome display. The SSD1303 provides three communication interfaces: 8-bit 6800/8080 parallel and SPI serial. The microcontroller sends commands and data through these interfaces to control the display.
**2.2 Power Supply Design**
The power supply circuit uses the TPS7333 DC-DC converter to step down 5V to 3.3V, which is used to power the SSD1303 and the microcontroller. The OLED requires 3.3V for logic and 9–12V for driving. The microcontroller (C8051F023) operates at 3.3V, while the OLED’s drive voltage is externally controlled. The MCU communicates with the SSD1303 through 13 control signals, including RES#, CS#, D/C, WR#, RD#, and D0–D7. These signals manage the OLED's operation, such as resetting, selecting the chip, and writing data or commands.
**2.3 Control Signals and Timing**
To simplify the control process, the WR# and RD# signals are connected to P0.7 and P0.6 of the C8051F023. In C programming, a pointer is defined as xdata type to access off-chip memory. By assigning the pointer to the external data storage area, the /RD and /WR signals are automatically activated during read/write operations. The address bus uses P1 and P2 ports depending on whether the system is in multiplexed or non-multiplexed mode. The timing waveform for reading and writing is shown in Figure 3, where data or command is written on the falling edge of WR# or RD# when CS# is low.
**3 Software Program Design**
The entire OLED display program is written in C language. The main program flow is shown in Figure 4. The microcontroller initializes the watchdog, clock, I/O ports, timers, and interrupts. The OLED initialization includes turning on the display, setting the display mode, adjusting contrast, and configuring the serial port. The GDDRAM is cleared before displaying any content. Before each write operation, the system checks if the OLED is busy by reading the highest bit (D7). If D7 is '1', the OLED is busy; otherwise, it is ready to receive new data.
**4 Text and Image Display**
The VGG12864G module has an internal 128×64-bit RAM for storing display data. The RAM is divided into 8 pages, with 8 lines per page. Each byte corresponds to one pixel, and the data directly drives the OLED display. To display text or images, a character library must be created. Font extraction software like "Word Extraction V2.2" can be used to generate the necessary dot matrix codes. The vertical mode is selected based on the RAM structure, and the font settings (size, underline, strikethrough) can be adjusted. The generated dot matrix code is then stored in the GDDRAM via the OLED display program, enabling stable and clear display on the screen.
**5 Conclusion**
This paper describes a method for implementing an OLED display using a single-chip microcontroller. The design successfully addresses the hardware and software requirements for text and image display. The experimental results confirm that the circuit is simple and cost-effective, making it suitable for small-scale devices. This approach demonstrates the feasibility of using OLEDs in various applications where compactness and performance are essential.
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