Yarm and alphanumeric LCD 16x2

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.

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 0x3E.

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

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

To install them in your Atmel Studio environment add

  • Daisy24_lib.c
  • Daisy24_lib.h

in the src folder of your project

Add also this minimal set of ASF library

Hello World !

#include <asf.h>
#include <stdint.h>
#include "Daisy24_lib.h"

int main(void)
{
	Daisy24_LCD_Init();
	delay_init();
	
	// Write "Hello World !"
	Daisy24_LCD_WriteString((char *)"Hello World !");
}

Set cursor position

#include <asf.h>
#include <stdint.h>
#include "Daisy24_lib.h"

int main( void)
{
	// Display init
	Daisy24_LCD_Init();
	delay_init();

	// Display clear
	Daisy24_LCD_Clear();
	
	// Set the cursor position to x=0,y=0 (top left) and write A
	Daisy24_LCD_SetCursor( 0, 0);
	Daisy24_LCD_WriteChar('A');
	
	// Set the cursor position to x=15,y=0 (top right) and write B
	Daisy24_LCD_SetCursor( 15, 0);
	Daisy24_LCD_WriteChar('B');

	// Set the cursor position to x=0,y=1 (bottom lefy) and write C
	Daisy24_LCD_SetCursor( 0, 1);
	Daisy24_LCD_WriteChar('C');

	// Set the cursor position to x=15,y=1 (bottom right) and write D
	Daisy24_LCD_SetCursor( 15, 1);
	Daisy24_LCD_WriteChar('D');

}

Backlight

#include <asf.h>
#include <stdint.h>
#include "Daisy24_lib.h"

int main( void)
{
	// Display init
	Daisy24_LCD_Init();
	delay_init();

	// Backlight off
	Daisy24_LCD_BkLightOff();
	Daisy24_LCD_SetCursor( 0, 0);
	Daisy24_LCD_WriteString((char *)"Backlight OFF");

	// Wait 1 secs
	delay_ms(2000);

	// Backlight on
	Daisy24_LCD_BkLightOn();
	Daisy24_LCD_SetCursor( 0, 0);
	Daisy24_LCD_WriteString((char *)"Backlight ON ");
}

If the backlight remains ON, change these lines in Daisy24_lib.c source.

//#define EXPANDER_I2C_ADDR       0x27    // PCF8574T
#define EXPANDER_I2C_ADDR       0x3F    // PCF8574AT

or viceversa

#define EXPANDER_I2C_ADDR       0x27    // PCF8574T
//#define EXPANDER_I2C_ADDR     0x3F    // PCF8574AT

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

Read push-buttons

#include <asf.h>
#include <stdint.h>
#include "Daisy24_lib.h"

int main( void)
{
	uint32_t p;
	
	// Display init
	Daisy24_LCD_Init();
	delay_init();
	
	Daisy24_LCD_WriteString((char *)"Press a button:");
	for (;;) {
		if (Daisy24_PB_Status(&p)==0) {
			if (p==0)  {
				Daisy24_LCD_SetCursor( 0, 1);
				Daisy24_LCD_WriteString((char *)"            ");
			}
			if 	(p==1) {
				Daisy24_LCD_SetCursor( 0, 1);
				Daisy24_LCD_WriteString((char *)"TOP LEFT    ");
			}
			if 	(p==2) {
				Daisy24_LCD_SetCursor( 0, 1);
				Daisy24_LCD_WriteString((char *)"TOP RIGHT   ");
			}
			if 	(p==8) {
				Daisy24_LCD_SetCursor( 0, 1);
				Daisy24_LCD_WriteString((char *)"BOTTOM LEFT ");
			}
			if 	(p==4) {
				Daisy24_LCD_SetCursor( 0, 1);
				Daisy24_LCD_WriteString((char *)"BOTTOM RIGHT");
			}
		}
	}
}

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

Links

Buy

DAISY-24
EUR 14.00


Alphanumeric I2C 16x2 LCD module + 4 push buttons

Daisy-24 mini alphanumeric I2C 16x2 characters LCD module with 4 push buttons. Usable as Terra Board front panel or as normal Daisy module for other board with Daisy connectors.

Note: the daisy flat cable to wire this board is not included. Don't forget to buy it (code FLAT-20CM). It is not needed if you plug it directly on a Terra board.

| Product description | Daisy catalog |

YARM-DEV
EUR 18.00


Evaluation board for YARM module

Carrier board for a rapid evaluation of the YARM radio module cababilities.

In includes the following parts:

  • MicroUSB port for power and data
  • ICP programmer port input
  • Double line of 14 pin pitch 2.54 mm for prototyping
| Product description || Flat price up to 999 pcs |

LCD-1
EUR 6.00


Mini size 16x2 characters I2C LCD

Winstar display model WO1602I-TFH-AT#

  • Black on white Alphanumeric characters: 16 colums x 2 lines
  • Backlight type: LED, White
  • LCD mode: FSTN positive
  • I2C interface
  • Power supply: 3.3 or 5 volt Datasheet
  • How to use it