Difference between revisions of "Matrix - I2C LCD1602"

Revision as of 14:30, 19 June 2016

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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

• Pin Description:

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:

• 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:

• 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 Applications

4.1 Connect to NanoPi M1

Refer to the following connection diagram to connect the module to the NanoPi M1:

Connection Details

4.2 Connect to NanoPi 2

Refer to the following connection diagram to connect the module to the NanoPi 2:

Connection Details:

4.3 Connect to NanoPi M2 / NanoPi 2 Fire

Refer to the following connection diagram to connect the module to the NanoPi M2/ NanoPi 2 Fire.

Connection Details:

4.4 Connect to NanoPC-T2

Refer to the following connection diagram to connect the module to the NanoPC-T2:
Matrix-I2C_LCD1602_NanoPC-T2

Connection Details:

5 Compile & Run Test Program

Boot your ARM board with Debian and copy the matrix code:

$ apt-get update && apt-get install git
$ git clone https://github.com/friendlyarm/matrix.git

If your cloning is done successfully a "matrix" directory will be generated.

Compile and install Matrix:

$ cd matrix
$ make && make install

Run test program:

$ matrix-lcd1602

Note: this module is not plug and play therefore before running the module please make sure it is connected to an ARM board.
Here is what you should observe:

The LCD will show the following two lines:
" B&G Char LCD"
"--by FriendlyARM"
If the LCD doesn't show them clearly you can adjust the resistor to highlight the characters.

6 Code Sample

This Matrix code sample can work with all the ARM boards mentioned in this module's wiki. The name of this code sample is "matrix-i2c_lcd1602". Here is its source code:

int main(int argc, char ** argv)
{
    int devFD, board;
    int i2cDev = 0;
 
    if ((board = boardInit()) < 0) {
        printf("Fail to init board\n");
        return -1;
    }
 
    if (argc == 2)
        i2cDev = atoi(argv[1]);
    if ((devFD = LCD1602Init(i2cDev)) == -1) {
        printf("Fail to init LCD1602\n");
        return -1;
    }
    if (LCD1602Clear(devFD) == -1) {
        printf("Fail to Clear\n");
    }
    printf("clearing LCD1602\n");
    sleep(1);
    if (LCD1602DispLines(devFD, "  B&G Char LCD", "--by FriendlyARM") == -1) {
        printf("Fail to Display String\n");
    }
    printf("displaying LCD1602\n");
    LCD1602DeInit(devFD);
    return 0;
}

For more details about this APIs called in this code sample refer to Matrix API reference manual

7 Connect to Arduino Board

7.1 Preparations

Make sure your Arduino board can work. Here is a reference link - https://www.arduino.cc/en/Guide/HomePage
Here we tried the Arduino Uno.

7.2 Hardware Connection

Refer to the following diagram to connect the Matrix-I2C_LCD1602 to an Arduino Uno

7.3 Compile & Run Test Program

All the matrix modules' code samples for Arduino are maintained on GitHub - https://github.com/friendlyarm/matrix-arduino.git
Clone the matrix code from GitHub

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

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

Copy the entire directory "matrix-i2c_lcd1602" to "Arduino_IDE/libraries"

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

Start Arduino IDE
Click on File->Examples->matrix-i2c_lcd1602->displaychar and run the test program.
Click on upload and run the test program.

7.4 Code Sample

#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()
{
}

8 Resources

LCD1602.pdf
pcf8574.pdf

9 Update Log

9.1 Feb-23-2016

• Added the description for "NanoPi 2 branch" in Section 4
• Added Section 5: Connect to NanoPi 2