Arduino I2C display

@ALL concerned about Serial LCD

Please see this post on the Arduino Playground: http://playground.arduino.cc/Learning/SparkFunSerLCD

It reinforces some things I first learned about the Serial LCD interface:

1. Character (byte) driven.

2. Can be treated like the Serial Monitor (within IDE).

Daniel

The connections seem right.

I had a look at Terry Kings site (yourduino.com) and found this relating to that version of display, that he also sells.

http://arduino-info.wikispaces.com/LCD-Blue-I2C#v2

The pin definitions may explain some of the issues.

BTW it is definately an I2C display and the library you have is set for the newer version of IDE.

Mark

Extract from TerryK's notebook:

//---(Following are the PCF8574 pin assignments to LCD connections )----

// This are different than earlier/different I2C LCD displays

#define BACKLIGHT_PIN  3

#define En_pin  2

#define Rw_pin  1

#define Rs_pin  0

#define D4_pin  4

#define D5_pin  5

#define D6_pin  6

#define D7_pin  7

#define  LED_OFF  1

#define  LED_ON  0

/*-----( Declare objects )-----*/ 

LiquidCrystal_I2C  lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);

The above expanded library interface makes clear to me that the vendors could have wired the 4 serial control and 4 data pins of the LCD any old way (actually 8! = 40,320 ways) they choose to onto the PCF8574's output pins.  So, why is it that the vendors don't provide that info to make their devices understandable and useable to the open source community?  Everyone, who has bought one of these I2C LCD units should contact the vendors and demand on behalf of the OS community that the interface between the PCF8574 output and LCD control/data lines be PUBLISHED on the web, IMHO.  

Extract from TerryK's notebook:

//---(Following are the PCF8574 pin assignments to LCD connections )----

// This are different than earlier/different I2C LCD displays

#define BACKLIGHT_PIN  3

#define En_pin  2

#define Rw_pin  1

#define Rs_pin  0

#define D4_pin  4

#define D5_pin  5

#define D6_pin  6

#define D7_pin  7

#define  LED_OFF  1

#define  LED_ON  0

/*-----( Declare objects )-----*/ 

LiquidCrystal_I2C  lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);

The above expanded library interface makes clear to me that the vendors could have wired the 4 serial control and 4 data pins of the LCD any old way (actually 8! = 40,320 ways) they choose to onto the PCF8574's output pins.  So, why is it that the vendors don't provide that info to make their devices understandable and useable to the open source community?  Everyone, who has bought one of these I2C LCD units should contact the vendors and demand on behalf of the OS community that the interface between the PCF8574 output and LCD control/data lines be PUBLISHED on the web, IMHO.  

The problem seems to be that pcf8574 is just an I/O expander so it can be wired up differently. The device I chose luckily had a ST7032 LCD controller chip so I did not have that issue but I still had an issue with the I2C address. I'm guessing that the backpacks take the expander approach because there is already a controller chip on the parallel LCD?

http://www.workshopshed.com/2012/07/a-little-venture-with-electronics-lcd.html

Since doing that I notice that on the Arduino site there is a I2C scanner which can obviously help with unknown devices.

http://playground.arduino.cc/Main/I2cScanner

Guys,

I checked the library, the library seems to be okay and working if we using Arduino 0022/0023 but not on Arduino 1.0.3.

Checked arduino forums, i2c (Wire) library is broken, the earlier i2c programs dont work in the new one.

Suggest, using ur own i2c functions or modding the library, i checked couple of different i2c chips which i had in hand, 24c04 (serial eeprom), ended up writing my own functions

cheers

sid

Strange

I've had mine working, and if you check it handles both versions.

The issue with the OP is the setup to pass the data.

Mark

I've also had no issues with different versions if the wire library, compiles ok with 1.0.3 -> 1.0.5.

I found with some very early examples I needed to change #include "WProgram.h" to be #include "Arduino.h" but otherwise no changes.

andy,

thanks for the correction, i am using arduino 1.0.1, it compiles with 1.0.3

cheers

sid

Billabot:

Thank you so much for all your help. I discovered that the enable and rs pins were inverted in my module. After several frustrating hours of library modificaion, I was finally able to get my display going.

Hooray!  Good job everyone.

Dan, you may, if you wish, select others to be rewarded with the Helpful Answer points recognition.  Please give credit where credit is due.

you resolve your problem ????????