i2c to lcd interface.pdf

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I2C to LCD interface

Here follows a short description on how to use my i2c_lcd library, with this you could use any

AVR circuit with a LCD with minimal extra hardware. The interface from the i2c to LCD

consists of a PCF8574 8bit I/O module, so with only 2 pins you could interface to the LCD.

The library replaces BASCOM:s LCD calls, so you only need to address the library and

configure the i2c pins and that’s it.

What you need to add in the beginning of your program is the following:

$lib "Lcd_i2c.lib"

Const Pcf8574_lcd = &H40

Config Scl = Portd.6

Config Sda = Portd.7

Dim _lcd_e As Byte

_lcd_e = 128

Yes, there is one thing added, the _lcd_e byte, it’s used to control which half of a 4-line LCD

to use, with 128 controlling the upper half (or a 2-line LCD) 64 controls the lower half and

192 when you what to control both halves at the same time (Cls, Deflcdchar)

The PCF8574 is connected as follows:

PCF8574

VDD

SDA

SCL

INT

P7

P6

+5V

A0

A1

A2

P0

P1

P2

P3

VSS

AVR- PortD.7

Gnd

AVR- PortD.6

LCD- D4

LCD- D5

n.c.

LCD- E1 (or E on 1 and 2 line LCD)

LCD- E2 (or n.c. on 1 and 2 line LCD)

P5

LCD- RW (not used, connected to give proper voltage)

LCD- D7

Gnd

P4

LCD- RS

A0, A1 and A2 gives the addres s of the chip

A0 A1 A2 Pcf8574_lcd

0 0 0 &H40

1 0 0 &H42

0 1 0 &H44

1 1 0 &H46

0 0 1 &H48

1 0 1 &H4A

0 1 1 &H4C

1 1 1 &H4E

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