1602 i2c controller not working with 20x4 HD44780 LCD – can you believe it?

I purchased two I2C 1602LCD controllers with PCF8574T chips (http://www.ebay.com/itm/310565362720) and two 20x4 character LCD display modules with HD44780 chips (http://www.ebay.com/itm/400448319287), but cannot get the controller to work with the LCD. I am using an UNO with Arduino IDE 1.6.4 and LiquidCrystal version 1.2.1from fmalpartida downloaded from bitbucket.org.
I have 4.6K resistors on SDA and SCL lines. I2c scanner returns 0x27 for address. i2cLCDguesser from https://forum.arduino.cc/index.php?topic=157817.0 was also tried (Thank you bperrybap for that.).
i2cLCDguesser behavior:
0x27 address is returned; Device PCF8574 is found
lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE) - blinks the screen three times, no output, screen is left highlighted
lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, NEGATIVE) - blinks the screen three times, no output, screen is left dark
lcd(0x27, 4, 5, 6, 0, 1, 2, 3, 7, NEGATIVE) – only a quick flash of the screen
lcd(0x27, 6, 5, 4, 0, 1, 2, 3, 7, NEGATIVE) – only a quick flash of the screen
lcd(0x27, 6, 5, 4, 0, 1, 2, 3, 7, POSITIVE) - only a quick flash of the screen
lcd(0x27, 4, 5, 6, 0, 1, 2, 3, 7, POSITIVE) - only a quick flash of the screen

I have tried both modules and LCDs. The behavior is the same.
I also downloaded LiquidCrystal version 1.1.7.1 and tried that….no luck.

Any suggestions on what to try next?

LCDTest3.ino (1.2 KB)

From the i2c guesser

  • For each guess it will re-initialize the display and
  • write the constructor to the serial port.
  • It will then attempt to blink the backlight 3 times.
  • Finally it will attempt to write the constructor used to the LCD.
  • When the correct configuration is guessed,
  • the LCD will display the constructor
  • and the backlight will be on.

According to the guesser, this is your constructor.

lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE) -  blinks the screen three times, no output, screen is left highlighted

Have you adjusted the contrast pot? You may not be seeing characters if the pot is not set correctly.

Well I'll be darned if that did not solve my problem. I thought I had adjusted the contrast before, but I thought, "well I'll try it again" and sure enough the output was there. Thank you for what was such a simple fix. Have a nice day.