BV4218B16x2	16 Character by 2 Line LCD display with and I2C and Keypad Interface.	Datasheet (BV4208)	£19.90
	This is a standard LCD display with an I2C (BV4218) controller attached. As well as driving the LCD display the module can also drive a 12 switch keypad.		Qty:

As can be seen from this picture of the back of the display. The 4 pins on the left hand side are the I2C interface and power connections. The straight row of pins next to that are the keypad interface pins that consists of 7 pins that can drive four rows by three columns which is used on a typical keypad. The 8th pin is an interrupt output pin that can be set up to change state if a key is pressed.

Shown here is the front of the display at switch on

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. Shown is the sign on message that is displayed at power up but as this is stored in programmable EEPROM this can be changed by the user. 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.

This is a typical wiring diagram, the LCD of course is already connected.

This interface uses a set of commands via the I2C bus that control various aspects of the device. Using this interface both DC and Stepper motors can be controlled.

This is a typical connection diagram for two DC motors that can be controlled bi-directionally. The two channels A (Y1 & Y2) and B (Y3 & Y4) can be independently pulse width modulated (PWM) to control the speed of each motor. Some example commands are:

I2C command set:

The I2C command set is very simple and follows the standard for the HD44780 LCD display controller. As an example sending a data command (1) followed by a LCD controller command of 1 will clear the display. There are free software examples written in VB script here, VB Script can be used with a web browser so with a suitable I2C interface (BV4221) the display can be controlled by the browser on a PC.

LCD Commands
1    Send LCD command
2    Send LCD data
3    Back light on/off
4    Print message in EEPROM
5    Display on/off
6    Message read

Keypad Commands
0x10    Key query
0x11    Get Key
0x12    Key Map start
0x13    Key down
0x14    Clear key buffer

System Commands
System commands allow reading and writing to the EEPROM that amongst other things can change the address of the device.

Features

• I2C 2 wire interface up to 400kHz
• Simple command set for direct control of LCD display
• Back light output up to 20mA
• Contrast trimmer
• 31 character input buffer for I2C commands
• 12 way cross point keypad interface
• Interrupt output or general purpose output
• 16 key keypad buffer
• User configurable I2C address
• User configurable key map
• Operating voltage 5.0V

Associated Products