B4R Library LiquidCrystal_I2C

Erel · May 2, 2016

This is a wrapper for this open source project: https://github.com/marcoschwartz/LiquidCrystal_I2C

It supports DFRobot I2C LCD displays.

Erel · Jul 31, 2016

Yes. The I2C pins on Arduino Mega are 20 and 21: https://www.arduino.cc/en/Reference/Wire

Hans- Joachim Krahe · Jul 31, 2016

perfect! thanks so much

Kevin · Jun 30, 2018

For anyone interested, I modified this library to support creating custom characters without the need for using inline C. I gave it a new name (rLiquidCrystal_I2C_Cust) but if Erel chooses, he can just merge the changes into an updated version of his library.

The original C library supports up to 8 custom characters, numbered 0-7.

I use this webpage to generate the characters. It has an option to output hex which seems to work best for me for creating the byte array in B4R. You can copy & paste the hex results, but you'll just need to remove the carriage returns after pasting into the IDE.

Code:

B4X:

Dim CharMap() As Byte = Array As Byte (0x00,0x1B,0x1B,0x00,0x11,0x1F,0x0E,0x00)
lcd.CreateChar (0, CharMap)

'To display the custom character, use this:
lcd.Write (Array As Byte(0))

derez · Jun 30, 2018

Kevin said:
For anyone interested, I modified this library to support creating custom characters without the need for using inline C. I gave it a new name (rLiquidCrystal_I2C_Cust) but if Erel chooses, he can just merge the changes into an updated version of his library.

The original C library supports up to 8 custom characters, numbered 0-7.

I use this webpage to generate the characters. It has an option to output hex which seems to work best for me for creating the byte array in B4R. You can copy & paste the hex results, but you'll just need to remove the carriage returns after pasting into the IDE.

Code:

B4X:

Dim CharMap() As Byte = Array As Byte (0x00,0x1B,0x1B,0x00,0x11,0x1F,0x0E,0x00) lcd.CreateChar (0, CharMap) 'To display the custom character, use this: lcd.Write (Array As Byte(0))

It doesn't work for me !

Kevin · Jun 30, 2018

derez said:
It doesn't work for me !

Perhaps post your code. I would think that it would work with any hardware that works with the original I2C library.

Cableguy · Jun 30, 2018

I2C screens have addresses, so you should start by that, check if your screen address is the one used in the code and if not change in the code to match your screen!

derez · Jun 30, 2018

The LCD works but it does not show the custom char. Using Arduino UNO.

B4X:

Sub Process_Globals
    'These global variables will be declared once when the application starts.
    'Public variables can be accessed from all modules.
    Public Serial1 As Serial
    Private lcd As LiquidCrystal_I2C
  
    Dim CharMap() As Byte = Array As Byte (0x00,0x1B,0x1B,0x00,0x11,0x1F,0x0E,0x00)
   
End Sub

Private Sub AppStart
   Serial1.Initialize(115200)
   Log("AppStart")
    lcd.Initialize(0x3F, 16, 2) 'based on the example from the project.
'   lcd.Initialize(0x27, 20, 4) ' for 20X4 lcd
   lcd.Backlight = True
   lcd.SetCursor(0,0)

    lcd.CreateChar (0, CharMap)
    lcd.Write (Array As Byte(0))
   
    lcd.SetCursor(0,1)
    lcd.Write("99999999")  ' this shows
 
End Sub

derez · Jun 30, 2018

Cableguy said:
I2C screens have addresses, so you should start by that, check if your screen address is the one used in the code and if not change in the code to match your screen!

Good idea but I know that of course.

Kevin · Jun 30, 2018

The only thing I can think of to try would be to uncheck the rLiquidCrystal_I2C_Cust library in the IDE, then right-click and choose Refresh, then re-check the rLiquidCrystal_I2C_Cust library to add it back in. Also, of course, be sure that you have already UN-checked the original rLiquidCrystal_I2C library.

Failing that, perhaps try cleaning the project.

Edit: While working on this change to the library, I recall reading that some people had issues using slot 0 with the original C library, so perhaps you can try changing it to use Slot 1 instead.

derez · Jul 1, 2018

Kevin said:
The only thing I can think of to try would be to uncheck the rLiquidCrystal_I2C_Cust library in the IDE, then right-click and choose Refresh, then re-check the rLiquidCrystal_I2C_Cust library to add it back in. Also, of course, be sure that you have already UN-checked the original rLiquidCrystal_I2C library.

Failing that, perhaps try cleaning the project.

Did all that - still nothing.

While working on this change to the library, I recall reading that some people had issues using slot 0 with the original C library, so perhaps you can try changing it to use Slot 1 instead.

I don't understand. I use pins A4 and A5 as sda and scl pins.

Kevin · Jul 1, 2018

derez said:
Did all that - still nothing.

I don't understand. I use pins A4 and A5 as sda and scl pins.

Replace the 0 with 1 (not in the array)...

B4X:

Dim CharMap() As Byte = Array As Byte (0x00,0x1B,0x1B,0x00,0x11,0x1F,0x0E,0x00)
lcd.CreateChar (0, CharMap)

'To display the custom character, use this:
lcd.Write (Array As Byte(0))

derez · Jul 1, 2018

OK but it didn't help either. Both rows show the regular chars (9999999 in my code) but not the custom char. Also tried to have 1 in the charmap.
I guess something in your library does not match with my UNO (a chinese clone), though I never had any compatibility problem with other libraries.

derez · Jul 1, 2018

Tried with WEMOS D1 - no luck there.

Cableguy · Jul 1, 2018

doesn't it need also the eeprom lib to be at least selected?

XorAndOr · Jul 2, 2018

derez said:

The LCD works but it does not show the custom char. Using Arduino UNO.

B4X:

Sub Process_Globals
    'These global variables will be declared once when the application starts.
    'Public variables can be accessed from all modules.
    Public Serial1 As Serial
    Private lcd As LiquidCrystal_I2C
 
    Dim CharMap() As Byte = Array As Byte (0x00,0x1B,0x1B,0x00,0x11,0x1F,0x0E,0x00)
  
End Sub

Private Sub AppStart
   Serial1.Initialize(115200)
   Log("AppStart")
    lcd.Initialize(0x3F, 16, 2) 'based on the example from the project.
'   lcd.Initialize(0x27, 20, 4) ' for 20X4 lcd
   lcd.Backlight = True
   lcd.SetCursor(0,0)

    lcd.CreateChar (0, CharMap)
    lcd.Write (Array As Byte(0))
  
    lcd.SetCursor(0,1)
    lcd.Write("99999999")  ' this shows
 
End Sub

Hello, set lcd.SetCursor(0,0) after lcd.CreateChar

B4X:

lcd.CreateChar(0, CharMap)

lcd.SetCursor(0,0)
lcd.Write(Array As Byte(0))

derez · Jul 2, 2018

XorAndOr said:
Hello, set lcd.SetCursor(0,0) after lcd.CreateChar

B4X:

lcd.CreateChar(0, CharMap) lcd.SetCursor(0,0) lcd.Write(Array As Byte(0))

That did it !
Thank you

Kevin · Jul 2, 2018

XorAndOr said:
Hello, set lcd.SetCursor(0,0) after lcd.CreateChar

B4X:

lcd.CreateChar(0, CharMap) lcd.SetCursor(0,0) lcd.Write(Array As Byte(0))

Good catch! I was pretty baffled as to why it wasn't working for him.

I create my characters just after initializing the lcd and long before I ever actually write to it.

derez · Jul 2, 2018

Thanks to all of you trying to help on this mystery...
The results - Hebrew letters:
If anyone is interested I can publish the byte arrays for all the letters.
This is how I write Sunday in Hebrew:

B4X:

Sub write_sunday
    lcd.CreateChar (0, resh)
    lcd.CreateChar (1, aleph)
    lcd.CreateChar (2, shin)
    lcd.CreateChar (3, vav)
    lcd.CreateChar (4, nuns)
    lcd.SetCursor(11,0)
    lcd.Write (Array As Byte(4,3,2,1,0))
End Sub

Note: There can be only 8 different custom chars on the screen at a time, for most of the words it enough but not for full screen text.

Cableguy · Jul 3, 2018

derez said:
There can be only 8 different custom chars on the screen at a time, for most of the words it enough but not for full screen text.

Isn't this an available memory issue?
I mean, with a wemos (4mB) you should be able to declare/store more custom characters, right?

derez · Jul 3, 2018

Cableguy said:
Isn't this an available memory issue?
I mean, with a wemos (4mB) you should be able to declare/store more custom characters, right?

The limit of 8 chars exists both in the original library and in Kevin's additions to it.

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