LCD1602 LCD display is a widely used character type LCD display module, and its LCD display circuit design involves multiple aspects. The following is a detailed analysis of the design: 1. Introduction to LCD1602
1. Composition: The LCD1602 liquid crystal display is composed of a character type liquid crystal display screen (LCD), a control driver main circuit HD44780 and its extended driver circuit HD44100, as well as a small number of resistors, capacitors, structural components, etc. assembled on a PCB board.
2. Display principle: By utilizing the physical properties of liquid crystals, the display area is controlled by voltage, and when there is electricity, there is display, thus displaying graphics. By controlling the voltage in different regions, the liquid crystals are rearranged to display various graphic images and characters.
3. Features: It has the characteristics of thin thickness, suitable for direct driving of large-scale integrated circuits, and easy to achieve full-color display. 2、 Pin function and circuit design
1. Pin function
LCD1602 typically has 16 pins, with the following pin functions: Pin 1 (VSS/GND): Ground pin. Pin 2 (VDD): Connected to a+5V power supply. Pin 3 (VO/VL): LCD display contrast adjustment terminal, with the weakest contrast when connected to a positive power supply and the highest contrast when grounded. Its contrast can be adjusted by connecting an external potentiometer. Pin 4 (RS): Register selection pin, select data register when high level and instruction register when low level. Pin 5 (R/W): Read/write signal line, performs read operation when high level and write operation when low level. Pin 6 (E/EN): Enable terminal, when the E terminal jumps from high level to low level, the LCD module executes the command. Pin 7 \ \~14 (D0 \ \~D7): an 8-bit bidirectional data line used by the microcontroller to write data to 1602 and read data from 1602. Pin 15: Positive pole of backlight source. Pin 16: Negative pole of backlight source.
The LCD1602 version with 14 pins also lacks backlight power (15 pins) and ground (16 pins) compared to the 16 pin version.
2. Circuit design power circuit: Typically, a+5V power supply is used to power the LCD1602. Contrast adjustment circuit: By connecting a potentiometer to the VO pin, the contrast of LCD1602 can be adjusted. Data interface circuit: Pin D0 \ \~D7 is connected to the data port of the microcontroller to achieve data read and write operations. The RS, RW, and E pins are respectively connected to the control ports of the microcontroller, used for selecting registers and performing read and write operations. Backlight circuit: If backlight function is required, pins 15 and 16 can be connected to the positive and negative poles of the power supply respectively, and a current limiting resistor may need to be added to protect the backlight. 3、 Display principle and instruction set
1. The display principle of LCD1602 is a character dot matrix display. In order to display the glyph of a character, it is necessary to have the font data of that character. The font data of characters is usually fixed in the Character Generator ROM (CGROM). The HD44780 has a built-in font for 192 commonly used characters. When displaying characters, the character code is sent to the Display Data RAM (DDRAM), and LCD1602 will read the corresponding font data from CGROM based on the character code and display it on the screen.
2. Command set clear screen command: Clear all displayed content on the screen. Return command: Reset the cursor and return it to address 00H. Set cursor and screen movement instructions: You can set the movement of the cursor and screen, such as self increase/decrease after cursor read/write operations, screen translation or no movement, etc. Set display, cursor, and flashing switch commands: You can set the status of display switches, cursor switches, and flashing switches. Cursor and screen movement command: can move the cursor or screen. Working mode setting instruction: used to initialize LCD1602, such as setting the number of data interface bits (8 or 4), display lines (1 or 2), and dot matrix character size (5 × 8 or 5 × 10), etc. 4、 Driver program design
Driver program design is the key to implementing the display function of LCD1602. Usually, it is necessary to use a microcontroller to write driver programs and control the display content by sending instructions and data to LCD1602. The design of the driver program includes functions such as initialization, screen clearing, displaying characters, and moving the cursor. 5、 Precautions
1. Timing requirement: LCD1602 is a slow display device, so before executing each instruction, it is necessary to confirm that the module's busy flag is low, indicating that the LCD is not busy at this time. Only then can instructions and data be written, otherwise this instruction will be invalid.
2. Power stability: In order to ensure the normal operation of LCD1602, a stable power supply voltage needs to be provided.
3. Contrast adjustment: When the contrast is too high, it will produce "ghosting". When using it, you can adjust the contrast through a 10K potentiometer to achieve the best display effect.
The design of LCD1602 LCD display circuit involves multiple aspects, including pin function and circuit design, display principle and instruction set, driver program design, and precautions. Through reasonable design and driver programming, the character display function of LCD1602 can be achieved.