multiple LCDs and special characters

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Hey folks,
I kinda struggle to get two i2c LCDs working seperately. Now when I display something on one LCD it is always displayed on both.

i2cdetect -y 1 always returns

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- 27 -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

But shouldn’t there two addresses? Or do I have two i2c modules with the same address?

Also: How do I display special chars on the display? e.g the degrees symbol or just a black block (█)? And is it possible to center the text?

best,
fletcher

Hi, @fletcher

I got a solution for you in terms of the address. I suppose you have an I2C Module on the back of your panel that looks like the one down below. As they come from the factory, they will all have the same address which is either 0x20 or 0x27, depending on the model.

To manipulate the address or get a different one, you will have to solder either 1,2 or 3 pins together as shown below. The bright red illustrates the area of the soldering spots, and the darker red stripes define the soldering lines which you can use to get a different address for you module.

As for the other questions about displaying special chars and the alignment there are various tutorials on how to use I²C LCDs with the Raspberry Pi or Arduino Platform. Maybe one of these can help you.

Regards,
Overflow

Hi @Overflow,
thanks for your detailed response.

Unfortunately there are no discribed pins. I have the following I²C panel:

(Source: Sainsmart.com)

Any ideas about that?

Hi @fletcher,

I’ve got no real knowledge of those Sainsmart LCD controllers (the black board on the back) but I think that there might not be an option to set another address from what I have red.

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

I got two of these working and they are pretty much the same. If you can wait for another 1-3 weeks, this might be an option for you to replace the board.

As far as I have learned about this saintsmart LCD it has no possibility to change the adress.
There are two adresses around 0x3F and 0x27 hardcoded but it’s not possible to change it.

@Overflow, @leader21.

Thanks to you both. I think I will order a different i2c module where I can change the addresses.

But as soon as they have different addresses, how can I control both seperately with pimatic? The plugin must be loaded as follows in the plugin section:

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

But where do I tell to use e.g address 39 and 27 so that I can use them in rules as “LCD 1” and “LCD 2”?

best,
fletcher

Oh well that’s the point … guess two LCD are not possible yet. If you double the plugin, Pimatic won’t start. So maybe some workaround with a shell script that writes the commands to a second LCD screen…
Don’t know if @sweetpi or @mwittig have a clue?

@leader21, @fletcher, @Overflow To support multiple LCDs, the plugin pimatic-lcd needs to be extended. The straightforward way of doing this is to introduce a LCD-Device rather than configure it through the plugin configuration. The tricky bit, however, is to support this in a backwards-compatible manner. I can do the necessary changes if needed.

@mwittig said:

@leader21, @fletcher, @Overflow To support multiple LCDs, the plugin pimatic-lcd needs to be extended. The straightforward way of doing this is to introduce a LCD-Device rather than configure it through the plugin configuration. The tricky bit, however, is to support this in a backwards-compatible manner. I can do the necessary changes if needed.

That would be great! I wonder why nobody asked this question before. I set up a pimatic dev system already myself but I think I lack some general pimatic plugin knowledge to accomplish this.

best,
fletcher

@fletcher i found in the Sainsmart user reviews a comment about this device how to change device addresses maybe this will help?

http://www.sainsmart.com/sainsmart-iic-i2c-twi-serial-2004-20x4-lcd-module-shield-for-arduino-uno-mega-r3.html#customer-reviews
"I used the I2C scanning program (google for it) and found that the LCD device address was 0x27, which when you shift to the left by one bit, resolves to 0x4E or 0x4F. Seems like they may have changed the device address to 0x4F in the last year."

@Pimagical I think the problem is that it is not possible to change the i2c address of the SaintSmart controller. If you have two controllers of the same batch you cannot use them on the same i2c bus. As @Overflow pointed out some controllers (different vendor) provide pins to change the address on the PCB.

Hello community,

today i found this topic with the search.
@mwittig Could you add multiple support for LCD displays?

with best regards
techsolo12

@techsolo12 said in multiple LCDs and special characters:

@mwittig Could you add multiple support for LCD displays?

It is supported already, see https://github.com/pimatic/pimatic-lcd/blob/master/lcd-config-schema.coffee
The only problem is that the config expects a number and JSON does not allow for writing a number as hex if I remember currectly. Thus you need to provide the address as decimal number. If you need help with the translation please post the address on this thread.

Note, beyond, the problem with the SaintSmart controller having hard coded addresses there is nothing we can do about on the pimatic side of things.

Thank you @mwittig for your fast response.
I don’t understand how i can adjust the second display.
My current display had hex 0x27 (decimal nr. 39) the other one 3f (decimal nr. 63).

with best regards
techsolo12

@techsolo12 Ups, sorry. You can only setup it once as it is tied to the plugin configuration

@mwittig Is it possible to add multiple support or is it to much work? I don’t know because i can’t program things like this.

With best regards
techsolo12