Matrix - I2C LCD1602

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1 Introduction

I2C LCD1602
I2C LCD1602
  • The Matrix-I2C_LCD1602 is an LCD display module composed of an LCD1602 and a PCF8574 module.
  • The LCD1602 can display up to 16x2 characters. It has a parallel interface.
  • The PCF8574 provides GPIO expansion up to 8 bit for I2C. It communicates with a master via I2C and converts data from the master to parallel signals to the LCD1602 thus controls the LCD's display and back light.

2 Features

  • I2C interface, LCD display and backlight control
  • 2.54mm spacing pin
  • IIC Module PCB dimension(mm): 16 x 42
  • LCD1602 PCB dimension (mm): 36 x 80

IIC模块PCB LCD1602 PCB

  • Pin Description:
Pin Description
SDA I2C SDA
SCL I2C SCL
5V Supply Voltage 5V
GND Ground

3 Basic Device Operation

3.1 PCF8574

  • The PCF8574 has I2C parallel expansion. It has an 8bit (P0 - P7) I2C interface.
  • The PCF8574 communicates with a master via I2C. The PCF8574's chip model is PCF8574T whose address specification is as follows:

PCF8574

  • If A2 - A0 are all set to 1 the 7bit address will be 0x27(0100111). By default RW is 0 and it is in the write mode.
  • In the write mode after opening the i2c-0 device and setting up its address the master can write data to it.
  • If you need to read data from it you will need to set the module to the read mode (RW set to 1). Please refer to the PCF8574's datasheet for more details.

3.2 LCD1602

  • The connection diagram between the PCF8574 module and the LCD module is as follows:

1602

  • RS is instruction/data register selection. RW is read/write selection. E is enable signal(edge triggering). BL is back light control. D4-D7 are data bits.
  • The LCD module is controlled by four data bits through which we can send instructions to control its state. Because it has eight instruction/data bits (DB7 - DB0) when writing each instruction/data we need to write the most significant four bits DB7 - DB4 first and then the least significant four bits DB3 - DB0.
  • Note: the LCD module has 192 most commonly used characters stored in CGROM. When we write a common character e.g "A" it will directly display "A". In addition it can store up to eight user defined characters in RAM called CGRAM.

4 Download Matrix Matrix Source Code

All the matrix modules' code samples are open source. They are maintained on GitHub - git://github.com/friendlyarm/matrix.git
Each branch in this hub contains the matrix modules' code samples for a board that the matrix modules can work with.

  • The nanopi branch contains the matrix modules' code samples for the NanoPi
  • The tiny4412 branch contains the matrix modules' code samples for the Tiny4412
  • The raspberrypi branch contains the matrix modules' code samples for the RaspberryPi

Install the git utility on a PC running Ubuntu14.04 

$ sudo apt-get install git

Clone the matrix code from GitHub 

$ git clone git://github.com/friendlyarm/matrix.git

If this is successful a "matrix" directory will be generated, which will contain all the matrix modules' code samples.

5 Connect to NanoPi

5.1 Preparations

Please install a Debian on a NanoPi and an appropriate cross compiler on a PC. Please refer to wiki:NanoPi
Compile a NanoPi kernel. Note: please use the kernel's source code from the nanopi-v4.1.y-matrix branch.

$ git clone https://github.com/friendlyarm/linux-4.x.y.git
$ cd linux-4.x.y
$ git checkout nanopi-v4.1.y-matrix
$ make nanopi_defconfig
$ touch .scmversion
$ make

5.2 Hardware Connection

Please refer to the following connection diagram to connect the Matrix-I2C_LCD1602 to the NanoPi
matrix-i2c_lcd1602_nanopi

Connection Details:

Matrix-I2C_LCD1602 NanoPi
SDA Pin3
SCL Pin5
5V Pin4
GND Pin6

5.3 Compile Test Program

Please login the matrix hub and enter the nanopi branch 

$ cd matrix
$ git checkout nanopi

Compile the matrix code 

$ make CROSS_COMPILE=arm-linux- clean
$ make CROSS_COMPILE=arm-linux-
$ make CROSS_COMPILE=arm-linux- install

Note: please make sure to install the cross compiler "arm-linux-gcc-4.4.3" on your PC, which is used to compile files for the NanoPi-Debian.
Generated library files are under the "install/lib" directory. Applications are under the "install/usr/bin" directory. The test program for the "Matrix-I2C_LCD1602" module is "matrix-i2c_lcd1602".

5.4 Run Test Program

Please copy the library files and test program to the NanoPi 

$ cp install/usr/bin/* nanopi_rootfs/usr/bin/
$ cp install/lib/* nanopi_rootfs/lib/ -d

Power on the NanoPi and run the following command in Debian's terminal
Note: this module is not plug and play therefore before running the module please make sure it is connected to a NanoPi. 

$ matrix-lcd1602

5.5 Code Sample

int main(int argc, char ** argv)
{
    int devFD;
    if ((devFD = LCD1602Init()) == -1) {
        printf("Fail to init LCD1602\n");
        return -1;
    }
 
    if (LCD1602Clear(devFD) == -1) {
        printf("Fail to Clear\n");
        return -1;
    }
    printf("clearing LCD1602\n");
    sleep(1);
 
    if (LCD1602DispLines(devFD, "  B&G Char LCD", "--by FriendlyARM") == -1) {
        printf("Fail to Display String\n");
        return -1;
    }
    printf("displaying LCD1602\n");
    LCD1602DeInit(devFD);
    return 0;
}

6 与Tiny4412连接使用

6.1 准备工作

参考Tiny4412光盘里的《友善之臂Ubuntu使用手册》，在Tiny4412上运行UbuntuCore系统，然后在主机PC上安装并使用相应的编译器。
注意：只能使用Tiny4412SDK-1506的底板。

6.2 硬件连接

参考下图连接模块Matrix-I2C_LCD1602和Tiny4412
matrix-i2c_lcd1602_tiny4412

连接说明：

Matrix-I2C_LCD1602 Tiny4412
SDA CON18 SDA
SCL CON18 SCL
5V CON18 5V
GND CON18 GND

6.3 编译测试程序

进入Matrix代码仓库，切换到tiny4412分支 

$ cd matrix
$ git checkout tiny4412

编译matrix配件代码 

$ make CROSS_COMPILE=arm-linux-gnueabihf- clean
$ make CROSS_COMPILE=arm-linux-gnueabihf-
$ make CROSS_COMPILE=arm-linux-gnueabihf- install

注意：请确保你的主机PC当前使用的交叉编译器为Tiny4412-UbuntuCore配套的arm-linux-gnueabihf-gcc-4.7.3。
编译出来的库文件位于install/lib目录下，而测试程序则位于install/usr/bin目录下，模块Matrix-I2C_LCD1602对应的测试程序为matrix-lcd1602。

6.4 运行测试程序

拷贝库文件和测试程序到Tiny4412的UbuntuCore的文件系统上 

$ cp install/usr/bin/* tiny4412_rootfs/usr/bin/
$ cp install/lib/* tiny4412_rootfs/lib/ -d

然后启动Tiny4412，在UbuntuCore的shell终端中执行如下命令运行模块Matrix-I2C_LCD1602的测试程序
注意：此模块并不支持热插拔，启动系统前需要确保硬件正常连接。 

$ matrix-lcd1602

6.5 代码展示

int main(int argc, char ** argv)
{
    int devFD;
    if ((devFD = LCD1602Init()) == -1) {
        printf("Fail to init LCD1602\n");
        return -1;
    }
 
    if (LCD1602Clear(devFD) == -1) {
        printf("Fail to Clear\n");
        return -1;
    }
    printf("clearing LCD1602\n");
    sleep(1);
 
    if (LCD1602DispLines(devFD, "  B&G Char LCD", "--by FriendlyARM") == -1) {
        printf("Fail to Display String\n");
        return -1;
    }
    printf("displaying LCD1602\n");
    LCD1602DeInit(devFD);
    return 0;
}

7 与RaspberryPi连接使用

8 与Arduino连接使用

8.1 准备工作

确保你的Arduino板能正常下载运行程序，参考：https://www.arduino.cc/en/Guide/HomePage
这里我们使用的是Arduino uno板。

8.2 硬件连接

参考下图连接模块Matrix-I2C_LCD1602和Arduino Uno
matrix-i2c_lcd1602_arduino

8.3 编译运行测试程序

由于arduino开发板并不运行Linux系统，所以matrix for arduino的代码由独立的仓库进行管理：git://github.com/friendlyarm/matrix-arduino.git
克隆matrix-arduino代码仓库 

$ git clone git://github.com/friendlyarm/matrix-arduino.git

克隆完成后会得到一个matrix-arduino目录，里面存放着所有Matrix 配件用于支持arduino的代码。

拷贝matrix-i2c_lcd1602目录到Arduino IDE的libraries目录下 

$ cd matrix-arduino
$ cp matrix-i2c_lcd1602 Arduino_IDE/libraies -r

启动Arduino IDE
点击File->Examples->matrix-i2c_lcd1602->displaychar，打开测试程序。
点击upload，运行测试程序。

8.4 代码展示

#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
 
// set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_I2C lcd(0x27,16,2);  
 
void setup()
{
  lcd.init();                        
  lcd.backlight();
  lcd.setCursor(2, 0);
  lcd.print("B&G Char LCD"); 
  lcd.setCursor(0, 1);
  lcd.println("--by FriendlyARM");
}
 
void loop()
{
}

9 相关资料

LCD1602.pdf
pcf8574.pdf


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