lcd display with i2c interface in stock

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If you’ve ever tried to connect an LCD display to an Arduino, you might have noticed that it consumes a lot of pins on the Arduino. Even in 4-bit mode, the Arduino still requires a total of seven connections – which is half of the Arduino’s available digital I/O pins.

The solution is to use an I2C LCD display. It consumes only two I/O pins that are not even part of the set of digital I/O pins and can be shared with other I2C devices as well.

True to their name, these LCDs are ideal for displaying only text/characters. A 16×2 character LCD, for example, has an LED backlight and can display 32 ASCII characters in two rows of 16 characters each.

If you look closely you can see tiny rectangles for each character on the display and the pixels that make up a character. Each of these rectangles is a grid of 5×8 pixels.

At the heart of the adapter is an 8-bit I/O expander chip – PCF8574. This chip converts the I2C data from an Arduino into the parallel data required for an LCD display.

If you are using multiple devices on the same I2C bus, you may need to set a different I2C address for the LCD adapter so that it does not conflict with another I2C device.

An important point here is that several companies manufacture the same PCF8574 chip, Texas Instruments and NXP Semiconductors, to name a few. And the I2C address of your LCD depends on the chip manufacturer.

According to the Texas Instruments’ datasheet, the three address selection bits (A0, A1 and A2) are placed at the end of the 7-bit I2C address register.

According to the NXP Semiconductors’ datasheet, the three address selection bits (A0, A1 and A2) are also placed at the end of the 7-bit I2C address register. But the other bits in the address register are different.

So your LCD probably has a default I2C address 0x27Hex or 0x3FHex. However it is recommended that you find out the actual I2C address of the LCD before using it.

Connecting an I2C LCD is much easier than connecting a standard LCD. You only need to connect 4 pins instead of 12. Start by connecting the VCC pin to the 5V output on the Arduino and GND to ground.

Now we are left with the pins which are used for I2C communication. Note that each Arduino board has different I2C pins that must be connected accordingly. On Arduino boards with the R3 layout, the SDA (data line) and SCL (clock line) are on the pin headers close to the AREF pin. They are also known as A5 (SCL) and A4 (SDA).

After wiring up the LCD you’ll need to adjust the contrast of the display. On the I2C module you will find a potentiometer that you can rotate with a small screwdriver.

Plug in the Arduino’s USB connector to power the LCD. You will see the backlight lit up. Now as you turn the knob on the potentiometer, you will start to see the first row of rectangles. If that happens, Congratulations! Your LCD is working fine.

To drive an I2C LCD you must first install a library called LiquidCrystal_I2C. This library is an enhanced version of the LiquidCrystal library that comes with your Arduino IDE.

Filter your search by typing ‘liquidcrystal‘. There should be some entries. Look for the LiquidCrystal I2C library by Frank de Brabander. Click on that entry, and then select Install.

The I2C address of your LCD depends on the manufacturer, as mentioned earlier. If your LCD has a Texas Instruments’ PCF8574 chip, its default I2C address is 0x27Hex. If your LCD has NXP Semiconductors’ PCF8574 chip, its default I2C address is 0x3FHex.

So your LCD probably has I2C address 0x27Hex or 0x3FHex. However it is recommended that you find out the actual I2C address of the LCD before using it. Luckily there’s an easy way to do this, thanks to the Nick Gammon.

But, before you proceed to upload the sketch, you need to make a small change to make it work for you. You must pass the I2C address of your LCD and the dimensions of the display to the constructor of the LiquidCrystal_I2C class. If you are using a 16×2 character LCD, pass the 16 and 2; If you’re using a 20×4 LCD, pass 20 and 4. You got the point!

First of all an object of LiquidCrystal_I2C class is created. This object takes three parameters LiquidCrystal_I2C(address, columns, rows). This is where you need to enter the address you found earlier, and the dimensions of the display.

In ‘setup’ we call three functions. The first function is init(). It initializes the LCD object. The second function is clear(). This clears the LCD screen and moves the cursor to the top left corner. And third, the backlight() function turns on the LCD backlight.

After that we set the cursor position to the third column of the first row by calling the function lcd.setCursor(2, 0). The cursor position specifies the location where you want the new text to be displayed on the LCD. The upper left corner is assumed to be col=0, row=0.

There are some useful functions you can use with LiquidCrystal_I2C objects. Some of them are listed below:lcd.home() function is used to position the cursor in the upper-left of the LCD without clearing the display.

lcd.scrollDisplayRight() function scrolls the contents of the display one space to the right. If you want the text to scroll continuously, you have to use this function inside a for loop.

lcd.scrollDisplayLeft() function scrolls the contents of the display one space to the left. Similar to above function, use this inside a for loop for continuous scrolling.

If you find the characters on the display dull and boring, you can create your own custom characters (glyphs) and symbols for your LCD. They are extremely useful when you want to display a character that is not part of the standard ASCII character set.

As discussed earlier in this tutorial a character is made up of a 5×8 pixel matrix, so you need to define your custom character within that matrix. You can use the createChar() function to define a character.

CGROM is used to store all permanent fonts that are displayed using their ASCII codes. For example, if we send 0x41 to the LCD, the letter ‘A’ will be printed on the display.

CGRAM is another memory used to store user defined characters. This RAM is limited to 64 bytes. For a 5×8 pixel based LCD, only 8 user-defined characters can be stored in CGRAM. And for 5×10 pixel based LCD only 4 user-defined characters can be stored.

After the library is included and the LCD object is created, custom character arrays are defined. The array consists of 8 bytes, each byte representing a row of a 5×8 LED matrix. In this sketch, eight custom characters have been created.

These displays are straightforward to use and are a great way to provide a user interface on many projects where you need more info than simple LED indicators or 7-Segment displays can provide since these are full alphanumeric displays with 2 lines of 16 characters each.  For an interactive display, pairing this type of display with a rotary encoder to navigate and select menu items on the display can provide a very nice user interface.

The display is composed of a 16 character x 2 line LCD display with a blue backlight and white characters.  Each of the characters are composed of a 5 x 8 dot matrix for good character representation.

The backlight has a potentiometer for adjustment of the contrast of the display for best viewing.  If the potentiometer is turned too far in one direction or the other, the display will appear blank or solid squares will appear instead of characters.  If this happens, just fiddle with the adjustment until it gives the best display.

Note:  The non-uniformity in the picture is due to the protective film covering the display playing a trick on the camera.  The display has nice uniformity.

This display incorporates an I2C interface that requires only 2 pins on a MCU to interface with and it has good library support to get up and running fast.   The I2C interface is a daughter board attached to the back of the LCD module.

If you need to adjust I2C address to avoid a conflict, this can be done on the I2C adapter board on the back of the module.  There are 3 address jumper locations marked A0, A1, A2.  Normally these lines are pulled high.  If you bridge these pads, it grounds that address line.  If you were to bridge all 3 to ground, the address would be 0x38 (or  0x20) depending on which version you have.  The range of all possible addresses spans from 0x38 – 0x3F or 0x20 – 0x27

These are good quality modules and should be in the parts bin of any hobbyist.  Because of the interactivity they provide, they are both fun to play with and useful for more serious projects.

We also offer the raw 16×2 displays without the I2C interface.  Those have a parallel bus interface that requires many pins on the MCU to control.  For most applications it is generally easiest to stick with the I2C interface version like this one.

Note that the I2C address of the module we sell is either 0x3F (63 decimal) or 0x27 (39 decimal) but can be adjusted if needed as explained above.  The address will be printed on the label on the bag.