Difference between revisions of "Matrix - I2C LCD1602"

Revision as of 08:27, 17 August 2015

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1 Introduction

I2C LCD1602

I2C LCD1602

This is an LCD module which has an I2C controller. It can display 16 x 2 characters. Its interface is parallel. To simplify its application we designed a controller on this module, which interfaces with other modules through I2C and transfers received signals to parallel signals to LCD1602. It can display, turn on and off back light.

2 Features

• I2C interface. It can display characters, and turn on and off back light
• 2.54 mm spacing pin
• I2C PCB dimension:16 x 42 mm
• LCD1602 PCB dimension: 36 x 80 mm

3 How They Work

3.1 PCF8574

• The PCF8574 module's interface is I2C parallel which is 8 bit and has 8 IO (P0 - P7) outputs.
• The PCF8574 module uses the PCF8574T chip whose address diagram is as follows:

• If you set A2-A0 all to "1" the address will be 0x27(0100111). By default RW is "0" and the module is in the "write" mode.
• If it is in the write mode and the address is set you can open "i2c-0" and write data to it.
• If you want to set it to "read" (RW set to "1") please refer to PCF8574's datasheet for more details

3.2 LCD1602

• The PCF8574 module's P0 - P7's pin spec are as follows:
• 由模块的原理图可以看出PCF8574模块的输出引脚P0-P7与LCD模块的引脚连接如下图：

• RS is command/data, RW is read/write, E is Enable(), BL is backlight and D4-D7 are data bits.
• RS为指令/数据控制位，RW为读/写控制位，E为使能位（边沿触发），BL为背光灯控制位，D4-D7为数据位。
• 由于LCD用到四个数据位，因此只能使用4线来驱动。通过指令表我们可以对LCD进行写指令设置LCD的工作转态，但这里的指令/数据（DB7-DB0）是八位的，而LCD却是4线驱动，因此每次写指令/数据时是先写高四位（DB7-DB4），再写低四位（DB3-DB0）。
• 注意：LCD内置了192个常用字模，存放在CGROM，所以我们在显示字符A时可以直接写入“A”，此外LCD还有8个允许用户自定义的字符产生的RAM，称为CGRAM，这里由于没有涉及到所以不介绍，有兴趣的用户可以去了解一下。

4 How To

4.1 Connection

• Connect to Tiny4412 SDK (1506)

GND: Ground

VCC: 5V

SDA: I2C SDA

SCL: I2C SCL

4.2 Code Sample in C Under Linux

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include "libfahw.h"
 
void test(char* line1, char* line2)
{
    int devFD;
    if ((devFD = LCD1602Init()) == -1) {
        printf("Fail to init LCD1602\n");
        return;
    }
 
            if (LCD1602Clear(devFD) == -1) {
                    printf("Fail to Clear\n");
                    return;
            }
 
    if (LCD1602DispLines(devFD, line1, line2) == -1) {
        printf("Fail to Display String\n");
        return ;
    }
 
    LCD1602DeInit(devFD);
}
 
int main(int argc, char ** argv) {
    int i;
    for (i=0; i<10; i++) {
         test("FriendlyARM", "From 2003");
         sleep(3);
    }
    return 0;
}

4.3 Compile and Run

git clone http://github.com/friendlyarm/fa-hardware.git
cd fa-hardware
cd demo
cd matrix-i2c_lcd1602
make

Copy your compiled bin to your board and you are ready to go.

5 Resources