I2C Scanner not working with arduino mega and Lcm1602 lcd 16x2

Hi. First off all, sorry for my english.

I'm trying to program "hello world" with arduino mega and Lcm1602 lcd 16x2, but I can't. The reason seem to be I can't find the I2C address of my display. I have tried with all i2c Scanner i've found, but no one find my two displays (i have one whith the i2c integrated module and another 16x2 lcd wired to a separate i2c module.

I'm using arduino mega 2560 and i connect sda and scl to 20 and 21 pin directly (no pull up resistors). I've tried to connect VCC to 3.3 and 5 v, but the scanner can not see the address.

Can anyone help me?

You can use the i2c_scanner in the playground and the i2c scanner at Nick Gammon's site.
The Arduino Mega 2560 has 10k pullup resistors on the board.

Can you check that pin 20 is connected to SDA and pin 21 to SCL, perhaps you exchanged them ? Did you connect the ground pin to the Arduino GND ?

Perhaps something is wrong with the displays or module. Can you give a link to them ?

did you also try - MultiSpeed I2C Scanner - 50,100,200,400 KHz. - Libraries - Arduino Forum -

It also checks at different bus speeds...

Peter_n:
You can use the i2c_scanner in the playground and the i2c scanner at Nick Gammon's site.
The Arduino Mega 2560 has 10k pullup resistors on the board.

Can you check that pin 20 is connected to SDA and pin 21 to SCL, perhaps you exchanged them ? Did you connect the ground pin to the Arduino GND ?

Perhaps something is wrong with the displays or module. Can you give a link to them ?

Thanks for your answer.

The wires are ok, and the pines SCL and SDA are in the correct place.

The display is:

And also tried with this one (the display is conected to):

http://www.dx.com/p/lcd1602-adapter-board-w-iic-i2c-interface-black-works-with-official-arduino-boards-216865#.VIc0_8l5W50

No one of them works. I tried with MultiSpeed I2C Scanner - 50,100,200,400 KHz. - Libraries - Arduino Forum - but when i try the script it freezes (stops) the loop and hang up the arduino.

When SDA is shortcut to SCL or one of them is shortcut to ground, all i2c scanners stop.
You could measure the voltage of SDA and SCL, while they are not being used. It should be near 5V.
Since the I2C-bus is a open-collector bus, you may shortcut SDA and SCL to ground and measure the short-current. You may also short one pin to ground and measure the voltage of the other, it should be near 5V.

If you don't connect anything, will the i2c scanner run ?