ESP8266 Community Forum

I have tried to connect a standard LCD (16X2lines) with a I2C-converter to the esp module.

the LCD backlight is on (at power up) and on run, it goes off and on again.
But nothing shown on the LCD.
I have been playing with the contrast-potmeter but I can't manage to show anything on the LCD.
Tried with/without 2 pullup-registers on SCL & SDA. (pins GPIO0 and GPIO2)
I found a nice utility from Sandfrog (viewtopic.php?f=40&t=7359) and it shows me I have a I2C adapter at addr hex27.
I am shure my LCD is working. I have tested it on a AVR on 4 and 8 bit-modus.

What converter is it using? It may not be compatible. I have seen that same effect with a python library for 16x2 i2c lcd that I wrote.

I found no version or model number on the PCB. But on the net I found this page: https://arduino-info.wikispaces.com/LCD-Blue-I2C
My model is the first on this page or a model1.
It is a simple pcb with a pcf8574 I/O expander. A0, A1 and A2 are pulled up with 10K resistor meaning 7bit I2C address=39
I tested it, connected to the ESP:

It sets/resets the bits of the output depending on the value of X, so I assume the converter is working.

Problem solved. It was a cheap PCB-board with bad solder on it.
Re soldered all the connections and the LCD is working fine now.

cheap buying isn't always the best option.