I2C LCD

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I have a problem with the device in a LCD pimatic .
I installed the plugin and connect the LCD . Unfortunately I get after entering a rule the following error :

error [pimatic]: Error on evaluation of rule condition of rule display1: Cannot write to device
error [pimatic]: rule display1 error executing an action: Cannot write to device

In my config I have the following entry (with address and without):

{
plugin:	lcd,
bus:	/dev/i2c-1,
address:	27,
rows:   4,
cols:     20
}

If no entry in the device-section of config necessary?

@Thrusty said:

If no entry in the device-section of config necessary?

The lcd plugin does not implement a device. Apart from the “address” your config is OK, Note, the address is a hexadecimal value. Thus, you need to set the address as follows: "address": 0x27.
Hope, this helps. Please keep me posted.

EDIT: Well, you said, you have also tried to omit the “address” property, right? I have checked the code which unfortunately does not handle the default value defined “lcd-config-schema.coffee”. So, I thinkl, the “address” property may not be omitted.

EDIT2: Note, he “bus” value needs to provided in quotes, i.e. "/dev/i2c-1" while the “address” value is given without quotes.

@mwittig Thank you , but it does not work unfortunately .
When I insert in the config 0x I get an error before saving ( code view ) .
If I put it in the " View " - insert changes pimatic entering 0x27 to 39
Unfortunately, this does not both.

{
      "plugin": "lcd",
      "bus": "/dev/i2c-1",
      "address": 39,
      "rows": 4,
      "cols": 20
    }

The quotes I had set correctly only not written in the code , sorry .

Edit: As I have now learned. When I type this there 0x27 is unfortunately no " number " more , but a “string” . The LCD requires a number. The BH1750 i2c sensor , the address input is a string.
What can I do ?

@Thrusty said:

As I have now learned. When I type this there 0x27 is unfortunately no " number " more , but a “string”

Ah, OK. I did not thought about this. The JSON specification does not allow for Numbers in hex and octal formats. So, the lcd-config-schema.coffee is misleading as it defines “address” as “number” with default 0x27. However, using the decimal value instead should be ok. You also tried to omit the “address” property, didn’t you? Well may be someone else can help? @sweetpi?

hey guys! i am not using the lcd right now, therefore i was looking for some plugin code at an old config file. i discovered this here :

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

there’s no adress given. I know that my LCD was working without any issues!
and also have a look here : https://github.com/pimatic/pimatic-lcd

@Thrusty

Are you sure the display has been successfully detected by raspi, i.e., did you check it using i2cdetect, for example?

Did you try to use the display using some other driver? If no driver provided with the display you can follow one of the various tutorials, for example, using http://www.raspberrypi-spy.co.uk/2012/07/16x2-lcd-module-control-using-python/ or http://www.raspberrypi-spy.co.uk/2012/07/16x2-lcd-module-control-using-python/

@mwittig I think the LCD has been recognized by Raspi.
I bought this HD44780. And the same description of the pages that link to with driver from the same page, sweetpi’s page.

Is it possible to change the file “lcd-config-schema.coffee”, so that the default may be entered as “string”?
Or maybe there was a LCD plugin version with which it worked differently? The bh1750 plugin is as I said, the address entry also a “string”.
How and where can I find older plugin?

Is there a tutorial how to connect a LCD to a RPi? Like what hardware is used/needed, how to connect LCD to RPi, is a driver needed to use the pimatic-lcd? I can’t find it.
Is it that simple to connect a LCD 16x2 with a i2c controller and connect as follow:
• SDA on Pin 3
• SDL on pin 5
• 5V on pin 2
• GND on pin 6
And install the plugin pimatic-lcd.
Will this be all?

enable i2c with sudo raspi-config tool, then hook it up and determine the adress with i2detect -y 1 if you don’t already now it.
you need to install the i2c-tools first if the above command doesn’t work out of the box sudo apt-get install i2c-tools
then set up the plugin at the config.json with the bus adress (without 0x at the beginning, if it’s 0x27 you don’t need to specifiy this since 0x27 is default).

{
      "plugin": "lcd",
      "bus": "/dev/i2c-1",
      "address": 27,
      "rows": 2,
      "cols": 16
},

this should do it.

And use level shifter . Raspberry not 5V .

hm… i remember using mine without a llc and working fine.
i read that powering with 3.3v could instead of 5v.

@leader21 said:

you need to install the i2c-tools first if the above command doesn’t work out of the box sudo apt-get install i2c-tools
then set up the plugin at the config.json with the bus adress (without 0x at the beginning,

Sorry, that’s not fully correct. The problem is that the config only accepts decimal numbers. So, for 0x23 you need to set the address property to 35 to make it work**. This is a flaw by design. On Windows you can use the desktop calculator for the conversion if you switch it to “programmer mode”.
** “A number is very much like a C or Java number, except that the octal and hexadecimal formats are not used.” JSON.org

Btw. I use the LCD on my Raspi without a level shifter power the LCD at 5V. Works fine fore me since months. However, if you have more than one I2C devices attached a level shifter is strongly recommended!

thx for clarification and sorry for misleading!!
haven’t had to set mine since it was ok by default.
maybe it’s a good thing to improve the readme on the plugin a bit.

@leader21 said:

maybe it’s a good thing to improve the readme on the plugin a bit.

Yes, absolutely. I also wanted to have a chat with @sweetpi on this. It would be better to have an address property of type string. This way a string to integer conversion (including hex to decimal conversion) can be done. Just wondering, whether or not a property type can be defined as “number” | “string”. The issue will be addressed as part of the next release for pimatic 0.9 https://github.com/pimatic/pimatic-lcd/pull/4.

I set up a plug-in via the web interface and I quitted an error too “rule display1 error executing an action gave an error message too: Can’t write to device” in case of such config

  "bus": "/dev/i2c-1",
  "rows": 2,
  "cols": 16,
  "plugin": "lcd",
  "active": true,
  "address": 39

it turned out because of it that the “plugin” is worth not at the beginning.
I delivered in the beginning and everything earned

  "plugin": "lcd",
  "bus": "/dev/i2c-1",
  "rows": 2,
  "cols": 16,
  "active": true,
  "address": 39

Can to whom it is useful=)

@mwittig @sweetpi does this really matter?!

it turned out because of it that the “plugin” is worth not at the beginning.

@leader21 said in I2C LCD:

does this really matter

no