Views: 293 Author: Site Editor Publish Time: 2024-03-20 Origin: Site
There are many ways to interface an MCU (Microcontroller Unit) or MPU (Microprocessor Unit) or CPU (Central Processing Unit) with an LCD.
Figure 1 Connection between MCU and LCD
The LCD cannot be driven with DC (direct current), it must be driven with AC (alternating current), and the total current must be zero. Otherwise, the liquid crystal material will be damaged sooner or later.
Figure 2 LCD driving waveform
There are two types of driver ICs, universal drivers and segment drivers. A universal driver outputs a signal to create a row or number of rows. Segment drivers output the necessary signals to create characters or columns.
The controller IC receives data written in ASCII or JIS code from the MPU and stores the data in RAM. This data is then converted into serial character mode and transferred to the LCD driver IC.
Driver/controller ICs are probably the most common among graphics modules. This IC receives data from MPU and stores it in RAM. Additionally, it accepts commands directly from the MPU for common and segment drivers.
Parallel interfaces can transmit multiple bits of data simultaneously, depending on the data bit width.
The serial interface can transmit one bit of data at a time
MCU interfaces include 6800 and 8080. 8080 is much more popular than 6800. The MCU interface generally consists of 4/8/9/16bits data (such as DB0, DB1,..., DB7; Note: 8bits is the most popular bit width), CS (chip select), RS (data register or instruction register selection) ), RD (read enable), WR (write enable).
Advantages: simple
Disadvantages: Requires memory, limited speed.
For Mono characters, graphics, small TFT (less than 3.5")
Figure 3 MCU/Parallel Interface
Serial interfaces include: I2C, SPI, RS232
Pros: Fewer connections, lower hardware costs
Disadvantages: Software is more complex
SPI (Serial Peripheral Interface bus) consists of the following 4 lines:
SCLK: serial clock (output from host);
moxi; master output, slave input (slave master output);
miso; master input, slave output (slave slave output);
SS: Slave selection
For singular, character, graphic LCD, small TFT, some CTP
Figure 4 4-wire SPI interface
Figure 5 3-wire SPI interface
I⊃2;C (Inter Integrated Circuit) consists of the following 2 connections.
SCL (Serial Clock Line),
SDA (Serial Data and Address Line).
For use with singular, character, graphic LCDs, small TFTs, and most capacitive touch screens.
Figure 6 IIC (I⊃2;C) interface
The RGB interface is often used to control large high-resolution LCD displays. It includes 6/16/18-bit data (such as R0, R1,,,G0,G1,,,B0,B1,,,,), VSYNC (vertical synchronization), HSYNC (horizontal synchronization).
The advantage is that R, G, and B data are written directly to the LCD without GRAM and are fast. Typically used for large, high-resolution LCD displays.
The disadvantage is that controlling the LCD is more complicated and requires more data lines than the MCU interface.
Application: Medium TFT (3.5” to 8”)
RGB interface includes 24-bit, 18-bit, and 16-bit.
Figure 7 RGB interface
LVDS (Low Voltage Differential Signaling) is an electronic digital signaling standard that can run at very high speeds over inexpensive twisted pair copper cables.
Most commonly used for large LCD Displays (>7 inch).
Figure 8 LVDS interface example
MIPI (Mobile Industry Processor Interface) Alliance, DSI (Display Serial Interface)
Designed to reduce the cost of display controllers in mobile devices. It typically targets LCD and similar display technologies. It defines the serial bus and communication protocol between the host (source of image data) and device (destination of image data)
The MIPI interface is becoming more and more popular.
Figure 9 MIPI interface example
DisplayPort (DP) is a digital display interface developed by an alliance of PC and chip manufacturers and standardized by the Video Electronics Standards Association (VESA). This interface is mainly used to connect video sources to display devices such as computer monitors, and can also carry various forms of data such as audio and USB.
DisplayPort is designed to replace VGA, DVI, and FPD-Link. The interface is backwards compatible with other interfaces such as HDMI and DVI through the use of active or passive adapters. It is mainly used for larger size and higher resolution displays.
Figure 10 eDP interface
A Universal Asynchronous Receiver/Transmitter (UART) is the circuit block responsible for implementing serial communications. Essentially, the UART acts as an intermediary between parallel and serial interfaces. On one end of the UART is a bus of eight or so data lines (plus some control pins), and on the other end are two serial lines - RX and TX.
Figure 11 URAT interface
Universal Serial Bus (USB) is a universal interface that enables communication between a device and a host controller, such as a personal computer (PC). It connects peripherals such as digital cameras, mice, keyboards, printers, scanners, media devices, external hard drives, and flash drives. The USB specification has had four generations: USB 1.x, USB 2.0, USB 3.x, and USB4.
It is widely used for capacitive touch screen connections.
Figure 12 USB interface
HDMI (High Definition Multimedia Interface) is a proprietary audio/video interface used to transmit uncompressed video data and compressed or uncompressed digital audio data from an HDMI-compatible source device (such as a display controller) to a compatible Computer monitor, video projector, digital television or digital audio equipment. HDMI is the digital replacement for the analog video standard.
As color TFT LCDs become more popular, HDMI is becoming more and more popular in the display industry.
Figure 13 HDMI interface
RS232 is a standard protocol for serial communication, used to connect computers and their peripheral devices to exchange serial data between them. Because it gets the voltage of the path used for data exchange between devices.
RS232 includes the following connections:
RX
VSS signal ground
VDD +5v
Figure 14 RS232 interface
Compared with later interfaces such as RS-422, RS-485 and Ethernet, RS-232 has lower transmission speed, shorter maximum cable length, larger voltage swing, larger standard connector, and no Multipoint capabilities and limited multipoint capabilities. In modern personal computers, USB has replaced RS-232 in most of its peripheral interface roles. Very few computers today are equipped with RS-232 ports, so you must use an external USB to RS-232 converter or an internal expansion card with one or more serial ports to connect RS-232 peripherals. Despite this, due to its simplicity and past ubiquity, the RS-232 interface is still used - particularly in industrial machines, network equipment, and scientific instruments where short-range, point-to-point, low-speed wired data connections are sufficient.
