#Yarm and alphanumeric LCD 16x2

<div class="text-success lead">
This article illustrates an example on how to use the I2C master bus on Yarm. We'll interface
a Daisy-24 module based on a Winstar I2C LCD and an I2C GPIO expander.
</div>

<img width="460px" src="./daisy24-pinout.jpg">

The Winstar LCD is compatible with the classic Hitachi HD44780 protocol but over an I2C bus instead of a parallel port
and its I2C address is <b>0x3E</b>.

* [Winstar WO1602I-TFH-AT# datasheet](http://terzo.acmesystems.it/download/datasheets/LCD-1.pdf)

The four push buttons and the LCD backlight are managed through a PCF8574T I2C GPIO expander 

* [Philips PCF8574 datasheet](http://terzo.acmesystems.it/download/datasheets/PCF8574.pdf)

The I/O expander I2C address depends on which chip is mounted on the board
as listed below:

* PCF8574AT = 0x3F
* PCF8574T = 0x27

In case you don't need push buttons it is possible to use just the Winstar LCD.

##Wirings

This is the list of wirings to link the DAISY-24 display to the YARM-DEV board:

| Yarm-dev pin # | SAM line          | Signal   | Daisy-24 |
|----------------|-------------------|----------|----------|
| 14             | GND               | GND      | GND      |
| 7              | PA8 (data line)   | I2C-SDA  | SDA      |
| 8              | PA9 (clock line ) | I2C-SCL  | SCL      |
| 28             | 3V3               | 3V3      | 3V3      |

## Code examples

In these examples we will use the [Cledic's Yarm libraries available on GitHub](https://github.com/cledic/YARM)

To install them in your Atmel Studio environment add 

* Daisy24_lib.c
* Daisy24_lib.h

in the <i>src</i> folder of your project  

Add also this [minimal set of ASF library](/yarm_asf_minimal_set)

### Hello World !

@source='hello.c'

### Set cursor position

@source='cursor.c'

### Backlight

@source='backlight.c'

If the backlight remains ON, change these lines in <b>Daisy24_lib.c</b> 
source.

<pre class="minicom">
//#define EXPANDER_I2C_ADDR       0x27    // PCF8574T
#define EXPANDER_I2C_ADDR	    0x3F	// PCF8574AT
</pre>

or viceversa 

<pre class="minicom">
#define EXPANDER_I2C_ADDR       0x27    // PCF8574T
//#define EXPANDER_I2C_ADDR	    0x3F	// PCF8574AT
</pre>

The right address depends from the I2C expander chip mounted on your Daisy24 module.

### Read push-buttons

@source='readbuttons.c'

If nothing happen pressing the buttons, read how to change the I2C expander address
in the backlight example.

## Links

* [Cledic's Daisy-24 libraries for Yarm](https://github.com/cledic/YARM/blob/master/main_daisy24.c)
* [DAISY-24 schematic](http://terzo.acmesystems.it/download/schematics/schematic_daisy24.pdf)
* [DAISY-24 product description](/DAISY-24)

## Buy

@shop='DAISY-24'
@shop='YARM-DEV'
@shop='LCD-1'