pcf8574 lcd module factory

A regular LCD requires a lot of wires (parallel interface) to be connected with a Microcontroller.The Serial LCD  backpack built on PCF8574 IC uses the I2C bus to convert  the parallel interface to a serial one.This needs only2 wires SDA & SCL , apart from the power connections.

The blue preset is to adjust the contrast of the LCD. The black jumper on the left is to enable the Backlight of LCD. The I2C device has a HEX address by which a microcontroller can communicate with it.This is set by the 3 bits A0,A1 ,A2 .If no jumper is present , it is HIGH &  a jumper means LOW. By default all the 3 jumpers are open . ie., A0,A1 A2 all are 1s.

lcd.setBacklightPin(HIGH);  makes the P3 pin go High, which turns on the NPN transistor.This provides GND to the LED pin of LCD As the other LED pin is already connected to Vcc through the jumper , the LCD backlight glows.

16×2 LCD is an alphanumeric display that can show up to 32 characters on a single screen. You can display more characters by scrolling the texts one by one. We have already seen how to connect LCD Display directly with the Arduino using 4bit and 8bit modes in our previous tutorial. But those two modes will utilize many numbers of GPIO Pins of our Arduino and we would have to end up with less number of pins for other sensors and actuators.

To overcome this problem we use LCD I2C backpack with our LCD. This I2C Backpack uses PCF8574 Remote 8 bit I/O Expander. It translates the data received from the I2C Bus into Parallel data that is needed for the LCD Display.

Inter-integrated Circuit (in short I2C) is a two-wire short distance communication protocol. You can use multiple slave devices in the same two wires with one or more master controllers. You may wonder how does the master identifies which slave does the data to be sent. In I2C the external devices have an I2C address for different external devices like LCD Backpack, OLED Display, etc. By using the address the data is sent to the specific device connected on the same I2C Bus.

There are totally 16 pins in an LCD Display. You can use directly all the pins in 8-bit mode with Arduino or 12 pins using 4-bit mode. In this tutorial, we use the I2C module for LCD and multiplex it into just 4 pins. This pin details might not be useful while using I2C Method but this is the actual pin details of all the pins in LCD Display.

RS – Register select. Specify what we are sending Command or Data. Sets to 0 for Command mode like setCursor, LCD Clear, TurnOFF LCD. Set 1 for data mode like sending Data/Characters.

First, we need to find the address of our I2C LCD Backpack. For that, we will be using I2C Scanner code to display the address in the serial monitor. Upload the following code, then note down the I2C address from the serial monitor.#include

Now the LCD I2C library is installed. We need to define and initialize the library using its associated functions. The steps is as follows. Or you can copy the code given below to print Hello World example.

Set the address that we copied from I2C Scanner code. The address I got is 0x27 so I replaced it to 0x27 in the following lineLiquidCrystal_I2C lcd(0x27, 16, 2);

In the above code, we have created an LCD object for ‘LiquidCrystal_I2C’. So you can use directly use the regular LCD functions to work with I2C like lcd.begin(), lcd.print(“”), etc.

To print a string we use lcd.print() function with string in its parameters. This prints ‘Factory’ string in the 1st row and ‘Forward’ in the 2nd row.

This function sets the cursor on 7th column and 2nd row. Printing the string will gets displayed from this location on LCD.lcd.setCursor(6,1); // Sets cursor column and row position

By Using lcd.blink() function we can make the cursor blinking on LCD. To turn off the blinking cursor we use lcd.noBlink() function.lcd.blink(); //Blinking cursor

Use lcd.cursor() function for printing an underscore symbol. It is also used for notifying users to enter some values.lcd.cursor(); // Prints an underscore symbol

This PCF8574 based module is a versatile I/O port expansion module. It is basically a I2C based port enpansion module which can convert any 8 bit data from I2C serial to 8-bit parallel. LCD if used with this module will require only 2 GPIO lines that will save a lot of hardware resources.

The next step is to download and install the Arduino I2C LCD library for use with the backpack. First of all, rename the "LiquidCrystal" library folder in your Arduino libraries folder. We do this just to keep it as a backup.

Now restart the Arduino IDE if it was already running - or open it now. To test the module we have a demonstration sketch prepared, simply copy and upload the following sketch:/* Demonstration sketch for PCF8574T I2C LCD Backpack

After a few moments the LCD will be initialised and start to display our URL and the value for millis, then blink the backlight off and on. If the text isn"t clear, or you just see white blocks - try adjusting the contrast using the potentiometer on the back of the module.

Using an LCD on a small chip like an attiny85 is not really that hard and till recent I didnt even think it warranted an instructable, but I have received questions about it, so I may as well expand on the process.

With the attiny only having a max of 6 pins available, it goes without saying that it cannot directly control all the pins of the standard Hitachi based LCD"s

A little bit over a year ago, I described how to add an LCD to an Attiny or other chip, using only 2 pins. That circuit made use of an HC164 shift register, but as I2C modules for LCD"s are extremely cheap and even LCD"s with a module already in place also are dirt cheap, one might as well use I2C on the Attiny85.

The "NewLCD" library from Francisco Malpartida is my favorite library, but also that one fails in using I2C for the Attiny because it makes a call to the Wire library. A modification to make it work with Attiny85 can be found here.

The "Bro Hogan" library however does work. It is basically the same library as the standard arduino LCD library, but it is modified to recognize the Attiny85 and the Attiny2313 and then makes a call to "TinyWireM" rather than "Wire".

Most problems you may encounter are related to the IDE getting confused regarding the libraries. If you are using the standard Arduino LCD library, best replace it by the Bro Hogan library. If you are using Malpartida"s library and want to keep that (as it is a great library), move it out of the way. Grab the entire folder and move it out of your sketchbook/libraries folder. Make sure you have the TinyWireM library installed and make sure your libraries are up to date.

If for whatever reason you cannot or do not want to move the Malpartida library out of the way, either rename the LiquidCrystal_I2C.h and LiquidCrystal_I2C.cpp modules in that library, or put the BroHogan LiquidCrystal_I2C.h and LiquidCrystal_I2C.cpp files in your sketch directory (and change the fishhook call into parenthesis).

This is a RoHS compliant I2C Serial LCD Daughter board that can be connected to a standard HD44780 compatible 16×2 , 20×4 or 20×2 Character Display Module that supports 4 bit mode. All Character Modules sold on our site support 4 bit mode, and nearly all commercially available 16×2 and 20×4 line character modules support it too.

There are many examples on internet for using this board with Arduino. Do a search for "Arduino LCD PCF8574". The I2C address is 0x3F by default, but this can be changed via 3 solder jumpers provided on the board. This allows up to 3 LCD displays to be controlled via a single I2C bus (giving each one it"s own address).

There are many Arduino libraries for a I2C display with the PCF8574 chip. We tested the library from Francisco Malpartida, and it works without any problems. For info see this page. We also made this library available on our site located here. To test this board with a LCD, do the following:

This device binding is meant to work with character LCD displays which use a HD44780 compatible controller. Almost all character LCDs fall into this category. Simple wrappers for 16x2 and 20x4 variants are included.

This binding should work and is in preview has been tested with a variety of 16x2 and 20x4 displays both in 4bit and 8bit mode and via i2C adapters (such as on the CrowPi). It should work with any character LCD with a 5x8 size character. Common names are 1602LCD and 2004LCD. Also supports Grove - LCD RGB Backlight.

These devices are controlled purely by GPIO (except Grove LCD RGB Backlight). There are two different types of GPIO pins that are used, the control pins, and the data pins. The data pins are the ones that will send out the text that should be printed out on the LCD screen. This binding supports two different configurations for the data pins: using 4 data pins, and using 8 data pins. When using only 4 data pins, we will require two send two messages to the controller, each sending half of the byte that should be printed.

var lcd = new Lcd1602(registerSelectPin: 0, enablePin: 2, dataPins: new int[] { 4, 5, 6, 7}, backlightPin: 3, readWritePin: 1, controller: controller);

For PCF8574T i2c addresses can be between 0x27 and 0x20 depending on bridged solder jumpers and for PCF8574AT i2c addresses can be between 0x3f and 0x38 depending on bridged solder jumpers

The sample code works with Adafruit"s I2C / SPI character LCD backpack which uses the Sn74hc595 8-bit shift register to support SPI communication. The pin parameters are set according to the backpack"s schematic.

Different samples are provided. The main method will use the Board"s Gpio pins to drive the LCD display. The second example will instead use an MCP Gpio extender backpack to drive the LCD display. Also the second example can use Grove RGB LCD Backlight via i2c bus. This second example has been tested on a CrowPi device and Grove LCD RGB Backlight device.

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