I find myself running around in circles and getting really fed-up.
These are some details that you might want to ask -
LCD 16x2 + backpack both from eBay (ATelec)
PC running Windows10 64bit
Sketches run to help i2C Scanner result - (0x27)
i2cLCDguesser result - 0x27,2,1,0,4,5,6,7,3 positive
LCD 20x4 produced the same results.
Although I am using IDE 1.0.6 now I have been through a great many in the past from 1.0 to 1.6.6 due to updates. 1.6.6 seem to cause too many problems for me so 1 went back to 1.6.4, still problematical. In the end I settled on 1.0.6 as this appeared to be more stable (according to a lot of other users).
I downloaded the NewLiquidCrystal library as recommended by everybody and got tid of the other liquid crystal libraries including any I2C LiquidCrystal libraries.
Success you might think but no. Now we start to show the problems. In a new sketch, select Examples.
Now select NewLiquidCrystal - select HelloWorld_i2c - click Verify - clunk! clunk! clunk!
This is an extract from the report, if i put in the full report my message is too big. Although it says its for ATtiny85 it's vrtually the same for Uno (Atmega 328)
This report would have more information with "Show verbose output during compilation" enabled in File > Preferences. Arduino: 1.0.6 (Windows NT (unknown)), Board: "ATtiny85 (internal 1 MHz clock)" C:\Program Files (x86)\Arduino 1.0.6\arduino-1.0.6\libraries\Wire\utility\twi.c: In function 'twi_init': C:\Program Files (x86)\Arduino 1.0.6\arduino-1.0.6\libraries\Wire\utility\twi.c:76: error: 'SDA' undeclared (first use in this function) C:\Program Files (x86)\Arduino 1.0.6\arduino-1.0.6\libraries\Wire\utility\twi.c:76: error: (Each undeclared identifier is reported only once C:\Program Files (x86)\Arduino 1.0.6\arduino-1.0.6\libraries\Wire\utility\twi.c:76: error: for each function it appears in.) C:\Program Files (x86)\Arduino 1.0.6\arduino-1.0.6\libraries\Wire\utility\twi.c:77: error: 'SCL' undeclared (first use in this function) C:\Program Files (x86)\Arduino 1.0.6\arduino-1.0.6\libraries\Wire\utility\twi.c:80: error: 'TWSR' undeclared (first use in this function) Massive I know, and I can't make head nor tail of it. I opened the vaious files .h and .cpp but I'm not a C programmer and I don't want to break things further, I feel that I've broken quite enough. Whilst I sound an absolute dunderhead in my defence I have another Uno with a sketch of my own which monitors atmospheric conditions in relation to my Astro telescope. I made my own shield with DHT11 and DS18B20 sensers. The DHT11 calculates dewpoint for me and the Dallas collects the temperature at the telescope lens. These data are used to calculate whether the dewshield (DIY) is switched on or off. An led is lit when this is necessary. Later I hope to automate this procedure using ATtiny's (not sure which one). All of the data is seen on a 20x4 LCD. Its all been functioning now for 2 years. Recently updated 2015. I don't know what to do, I need help Thanks Danny