Control the liquid crystal display module LCD1602 with a single chip microcomputer

Single chip microcomputer STM32L151CCU6

L0504-Murata muRata common mode inductor 90Ω 150mA

The liquid crystal display module has the advantages of small size, low power consumption, rich display content, ultra-thin and light weight, and has been widely used in pocket-type instruments and low-power application systems. Now the character-type liquid crystal display module is already a single-chip application. The most commonly used information display device in the design.

Introduction to LCD1602

Here to introduce the LCD1602 character type liquid crystal display module, it can display two lines, each line of 16 characters, equivalent to 32 LED digital tube, and more than the information displayed by the digital tube. It is powered by a single +5V power supply. The peripheral circuit configuration is simple, the price is cheap, and it has a high cost performance. The 1602 pin is shown in the figure below. The function of each pin is shown in the following table. The main pin functions are as follows:

VO: LCD contrast adjustment end, the contrast of the positive power supply is the weakest; the contrast is highest when the grounding power supply. When the contrast is too high, "ghosting" will occur, and the contrast can be adjusted by a potentiometer of about 5k. RS: Register selection, select the data register when high level; select the instruction register when low level.

R/W: Read and write signal line, read operation when high level, write operation when low level. When RS and R/W are low together, the instruction or display address can be written; when Rs is high and R/W is low, data can be written.

E: Enable terminal. When the E terminal changes from high level to low level, the liquid crystal module executes the command. The LCD1602 has 11 control commands, the functions of which are shown in the table below.

Here are just a few instructions that are often used during programming:

1. Clear screen (see table below)

2. Display switch control (see table below).

Function: Set display, cursor and blinking on and off.

Where: D indicates the display switch: D=1 is on, D=0 is off;

C indicates the cursor switch: C=1 is on, C=0 is off,

B indicates a flashing switch: B=1 is on and B=O is off.

3. cursor. Screen shift (see table below)

Function: Cursor, screen movement, does not affect DDR_AM.

Where: S/C=1: the picture is shifted by one character bit;

S/C=0: The cursor is shifted by one character bit;

R/L=1: right shift; R/L: O: left shift.

4 assist settings (see table below)

Function: Working mode setting (initialization command).

Where: DL=1, 8-bit data interface; DL=0, four-bit data interface;

N=1, two lines are displayed; N=0, one line is displayed;

F=1, 5×10 dot matrix characters; F=0, 5×7 dot matrix characters.

Read and write register

The control timing of the read and write registers is shown in the table below.

1. Write command function: write control word to register

Typical circuit

The typical circuit connections for the LCD1602 are shown below.

Description: Data line

DB0~DB7 are connected to the P0 port of the single-chip microcomputer; the three control lines are respectively connected to P1.5, P1.6, P1.7 (these control lines can be modified according to the specific hardware circuit), and the resistor R1 is used to adjust the liquid crystal display The contrast can be adjusted by a 5k potentiometer. The resistor R2 is used to set the brightness of the backlight. Generally, a 1k resistor can be used. Of course, the potentiometer can be connected to adjust the brightness of the display. Tip: Generally, in the circuit design, the liquid crystal is rarely directly implemented on the circuit board of the single chip microcomputer, but is transferred through an interface circuit, for example, a 16-line interface is left on the main board, so that a group of 16 can be passed. The root of the cable to connect the microcontroller and LCD.

driver

The drivers here mainly include:

1. LCD initialization function: set the working mode of the LCD

2. Set display coordinates: set the display position of characters, row and column coordinates

3. Write character function: write a character to the LCD

4. Write string function: write string to liquid crystal

Parameters: x-column coordinates, y-row coordinates, *s- characters to be displayed

data

Void LCD_write_string(unsigned char x,

Un8igned char y,unsi. Gned char*s)

{

LCD_set_xy(x,y);//First set the display coordinates

While(*s)//Check if it is over

{

LCDIO=*s;//Cycle call write data function

LCD_en_dat(*s);

8++:

}

}