lcd 1602A with i2c adapter (mjkdz) don't write caracters [solved]

Other Hardware Displays
1

i used officials libraries LiquidCrystal_I2C and hd44780 (I2Cexpdiag)

backlight is useful but that's all !

800×450 133 KB

2

And so what did I2CexpDiag show?
Did you try adjusting the pot?
That pot will require many turns to make a difference.
At one end you will see no pixels, at the other, all pixels will always be on.
Somewhere in between the pixels will work as expected.

That is an odd way to solder the backpack. The pin orientation isn't changed, but usually the backpack is soldered so the
backpack doesn't stick up above the LCD PCB.
On that backpack (and I have few them), I replace the pot and relocate it.

  • I don't like multi turn pots for LCDs
  • I want the pot on the other side of the backpack PCB
    Moving the pot allows it to be accessed when the backpack is flipped/rotated around so the chips on the backpack face the LCD module
    and the backpack won't stick out beyond the LCD module.

--- bill

3

Did you adjust the contrast with the pot? Out of the box, the contrast is normally set too light to see. Even if the Arduino isn't doing it's job printing to it, on power on you'll see a row of black boxes on the screen that you can use to make sure your contrast is adjusted right.

4

I2CexpDiag show :

Scanning i2c bus for devices..
i2c device found at address 0x20
Total I2C devices found: 1

Scanning i2c bus for all lcd displays
LCD at address: 0x20 | config: P65401237L | R/W control: Yes
Total LCD devices found: 1

...
Compare error: addr: 66 read 22 != wrote 66
Compare error: addr: 67 read 22 != wrote 67
FAILED

No working LCD devices

5

800×447 166 KB

6

Does the contrast pot work? and vary the contrast?
If not the backpack was soldered on backwards with all the pins reversed.

Can you post a photo of the other side?
I want to take a look to make sure the backpack wasn't soldered backwards.

--- bill

7

yes contrast pot work.

8

dvarrel:
yes contrast pot work.

So you are saying that when you turn it all the way to one end all the pixels turn off, and all the way to the other end all the pixels are on?

You still have not posted the I2CexpDiag output or a photo of the other side.

--- bill

9

i2cexpdiag : message #3

i found it : RW pin was not solded proprely

thanks for all

10

That is an odd way to solder the backpack.

It must be the correct way, look at this Instructable.

Don

11

16x2 modules commonly have headers at the top left of the display.
Other modules have headers at bottom right.

I suspect that this mkjdz adapter is designed for bottom-right modules.
Whichever style of adapter / module is used, you can stop short-circuits by slipping paper or thin plastic between the two pcbs.

Hey-ho. The OP has got it working now.

David.