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I2C 20X4 lcd blue display & kepad interface
I2C 20 x 4 Blue LCD Display with Keypad Controller
This is a complete LCD display ready to go, just send I2C commands.
The display has 20 characters by 4 lines. It has a white LED back light that projects white letters on a blue background as shown. It uses an I2C controller, that can also be purchased separately if required. The controller module also has the capability of being connected to a keypad. The full datasheet for the controller can be found at http://www.i2c.byvac.com/downloads/BV4218%20DataSheet.pdf A standard keypad can be attached to the interface to provide input without causing any overhead on the CPU.
The above is what you get, the controller fitted to the display, this is the back view and the I2C & power pins can be seen ready for connection.
The keypad is not supplied or fitted but this is an example of fitting a 12 way keypad to the controller so the display can input as well as output information, access to the key values and display are all through simple I2C commands.
The display and keypad are all controlled from the I2C, 2 wire interface. The I2C address is user configurable in software and held in EEPROM. There is a sign on message area so that at power up a user message can be displayed. The keypad it takes is a standard cross point type with 4 rows and three columns. The key scan codes are mapped to an area of EEPROM so that the user can modify the value that is returned for each key press.
There is a 16 key key buffer so that the host CPU does not need to constantly poll the device. An interrupt output goes low whenever there is a key in the key buffer.
Typical wiring scheme. The only external components that are required are the two pull up resistors required for the I2C bus.
System commands allow reading and writing to the EEPROM that amongst other things can change the address of the device.
* A 20 x 4 Blue LCD with the I2C serial display controller fitted
* CD-ROM with datasheets and other software
* I2C 2 wire interface up to 400kHz
* Simple command set for direct control of LCD display
* Contrast trimmer ***** NOTE ON THE 4 LINE DISPLAY THE CONTRAST IS AUTOMATIC ***
* 12 way cross point keypad interface
* Interrupt output or general purpose output
* User configurable I2C address
* Operating voltage 4.5 to 5.5V
* Operating current @5V, 7mA no BL, 27mA with BL on
