Ic2 16x2 display Input/Output Error

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And another question…

I bought a 16x2 display

http://www.tinytronics.nl/shop/Display/LCD-Display-16*2-karakters-met-witte-tekst-en-blauwe-backlight

connected it with the ic2 board :

• SDA on Pin 3
• SDL on pin 5
  -5V on pin 2
• GND on pin 6

http://www.tinytronics.nl/shop/Display/LCD-Connection-to-I2C-Module

sudo echo "i2c-bcm2708" >> /etc/modules
sudo echo "i2c-dev" >> /etc/modules

sudo nano /etc/modprobe.d/raspi-blacklist.conf

and comment out the lines below:

#blacklist spi-bcm2708
#blacklist i2c-bcm2708

after a reboot I installed some utils:

sudo apt-get install python-smbus
sudo apt-get install i2c-tools

and the with this command:

sudo i2cdetect -y 1

I get this result:

 0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f

00: – -- – -- – -- – -- – -- – -- –
10: – -- – -- – -- – -- – -- – UU – -- – --
20: – -- – -- – -- – -- – -- – -- – -- – --
30: – -- – -- – -- – -- – -- – -- – -- – --
40: – -- – -- – -- – -- – -- – -- – -- – --
50: – -- – -- – -- – -- – -- – -- – -- – --
60: – -- – -- – -- – -- – -- – -- – -- – --
70: – -- – -- – -- – --

So then, I try this:

sudo python lcd_i2c.py

But get the following error:

Traceback (most recent call last):
  File "lcd_i2c.py", line 135, in <module>
    lcd_byte(0x01, LCD_CMD)
  File "lcd_i2c.py", line 83, in lcd_byte
    bus.write_byte(I2C_ADDR, bits_high)
IOError: [Errno 5] Input/output error

And I’m lost …

Probably not specific for PiMatic but if I cannot have this working, I doubt if it will work with Pimatic…

Thanks for helping out (again)

@vanturenhout I think you have to specify the I²C address of the converter.
In the documentation it is declared as “0x3F”.

But the Detect values looks not right.

Sorry for the dumb question, but where do I change/specifiy this ?

I haven´t worked with an I²C Display yet. But when i look at this file
https://bitbucket.org/MattHawkinsUK/rpispy-misc/raw/master/python/lcd_i2c.py
In line 39 is this entry
I2C_ADDR = 0x27 # I2C device address

This you must change to 0x3F

There is also an tutorial
http://www.raspberrypi-spy.co.uk/2015/05/using-an-i2c-enabled-lcd-screen-with-the-raspberry-pi/

The tutorial you point me to,I have followed that. The only thing I’m missing there is the leveler but I don;t think I need that for this. I connected the lcd via the I2C on the GPIO. It’s shining bright

I believe that the change in the py file will only help for the test,but will not fix the Detect values, am I right?

I don’t understand the translation from the table displayed with

sudo i2cdetect -y 1

to 0x37. Do you see in that table that the detection is not correct?

@vanturenhout Oh, i switched the SDA and SDL

SDA on Pin 5
SDL on pin 3

Now this is the result:

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- UU -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 3f
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

I changed the py file to 0x3f and I see some live on the display, and no error in the CLI…Next step: See if I can get something readable on the display

Nice, now you got a valid address.
Dose the test work now?

But i have bad news for you. The pimatic-lcd plugin lacks the support of different I²C addresses. I look what we can make to solve this for you.

@Icesory

Well, I see a cursor blinking but I do not see the text I was expecting…

@Icesory Ok, is that why I see the error:

rule lcd-test error executing an action: Cannot write to device

??

i was wrong, Pimatic-lcd has support for different addresses.

The config should be this for your 16x2 LCD

{
  "plugin": "lcd",
  "bus": "/dev/i2c-1",
  "address": 0x3F,
  "rows": 2,
  "cols": 16
}

Pimatic doesn’t give errors anymore, the py program doesn’t also. But the LCD only shows some blinking lines and sometimes a blinking cursor. I tried turning the pot meter for brightness, but that didn’t help either…

That is strange. Eventually it is really a voltage problem. As I mentioned before, I have no experience with the I2c displays.

@Icesory I understand, but you helped me out really well, so thanks for that.