TCP/IP - LCD 20x4 Bricklet

This is the description of the TCP/IP protocol for the LCD 20x4 Bricklet. General information and technical specifications for the LCD 20x4 Bricklet are summarized in its hardware description.

API

A general description of the TCP/IP protocol structure can be found here.

Basic Functions

BrickletLCD20x4.write_line
Function ID:

1

Request:
  • line -- uint8
  • position -- uint8
  • text -- char[20]
Response:

no response

Writes text to a specific line (0 to 3) with a specific position (0 to 19). The text can have a maximum of 20 characters.

For example: (0, 7, "Hello") will write Hello in the middle of the first line of the display.

The display uses a special charset that includes all ASCII characters except backslash and tilde. The LCD charset also includes several other non-ASCII characters, see the charset specification for details. The Unicode example above shows how to specify non-ASCII characters and how to translate from Unicode to the LCD charset.

BrickletLCD20x4.clear_display
Function ID:2
Request:empty payload
Response:no response

Deletes all characters from the display.

BrickletLCD20x4.backlight_on
Function ID:3
Request:empty payload
Response:no response

Turns the backlight on.

BrickletLCD20x4.backlight_off
Function ID:4
Request:empty payload
Response:no response

Turns the backlight off.

BrickletLCD20x4.is_backlight_on
Function ID:

5

Request:

empty payload

Response:
  • backlight -- bool

Returns true if the backlight is on and false otherwise.

Advanced Functions

BrickletLCD20x4.set_config
Function ID:

6

Request:
  • cursor -- bool
  • blinking -- bool
Response:

no response

Configures if the cursor (shown as "_") should be visible and if it should be blinking (shown as a blinking block). The cursor position is one character behind the the last text written with write_line.

The default is (false, false).

BrickletLCD20x4.get_config
Function ID:

7

Request:

empty payload

Response:
  • cursor -- bool
  • blinking -- bool

Returns the configuration as set by set_config.

BrickletLCD20x4.is_button_pressed
Function ID:

8

Request:
  • button -- uint8
Response:
  • pressed -- bool

Returns true if the button (0 to 2 or 0 to 3 since hardware version 1.2) is pressed.

If you want to react on button presses and releases it is recommended to use the CALLBACK_BUTTON_PRESSED and CALLBACK_BUTTON_RELEASED callbacks.

BrickletLCD20x4.set_custom_character
Function ID:

11

Request:
  • index -- uint8
  • character -- uint8[8]
Response:

no response

The LCD 20x4 Bricklet can store up to 8 custom characters. The characters consist of 5x8 pixels and can be addressed with the index 0-7. To describe the pixels, the first 5 bits of 8 bytes are used. For example, to make a custom character "H", you should transfer the following:

  • character[0] = 0b00010001 (decimal value 17)
  • character[1] = 0b00010001 (decimal value 17)
  • character[2] = 0b00010001 (decimal value 17)
  • character[3] = 0b00011111 (decimal value 31)
  • character[4] = 0b00010001 (decimal value 17)
  • character[5] = 0b00010001 (decimal value 17)
  • character[6] = 0b00010001 (decimal value 17)
  • character[7] = 0b00000000 (decimal value 0)

The characters can later be written with write_line by using the characters with the byte representation 8 ("x08") to 15 ("x0F").

You can play around with the custom characters in Brick Viewer version since 2.0.1.

Custom characters are stored by the LCD in RAM, so they have to be set after each startup.

New in version 2.0.1 (Plugin).

BrickletLCD20x4.get_custom_character
Function ID:

12

Request:
  • index -- uint8
Response:
  • character -- uint8[8]

Returns the custom character for a given index, as set with set_custom_character.

New in version 2.0.1 (Plugin).

BrickletLCD20x4.set_default_text
Function ID:

13

Request:
  • line -- uint8
  • text -- char[20]
Response:

no response

Sets the default text for lines 0-3. The max number of characters per line is 20.

The default text is shown on the LCD, if the default text counter expires, see set_default_text_counter.

New in version 2.0.2 (Plugin).

BrickletLCD20x4.get_default_text
Function ID:

14

Request:
  • line -- uint8
Response:
  • text -- char[20]

Returns the default text for a given line (0-3) as set by set_default_text.

New in version 2.0.2 (Plugin).

BrickletLCD20x4.set_default_text_counter
Function ID:

15

Request:
  • counter -- int32
Response:

no response

Sets the default text counter in ms. This counter is decremented each ms by the LCD firmware. If the counter reaches 0, the default text (see set_default_text) is shown on the LCD.

This functionality can be used to show a default text if the controlling program crashes or the connection is interrupted.

A possible approach is to call set_default_text_counter every minute with the parameter 1000*60*2 (2 minutes). In this case the default text will be shown no later than 2 minutes after the controlling program crashes.

A negative counter turns the default text functionality off.

The default is -1.

New in version 2.0.2 (Plugin).

BrickletLCD20x4.get_default_text_counter
Function ID:

16

Request:

empty payload

Response:
  • counter -- int32

Returns the current value of the default text counter.

New in version 2.0.2 (Plugin).

BrickletLCD20x4.get_identity
Function ID:

255

Request:

empty payload

Response:
  • uid -- char[8]
  • connected_uid -- char[8]
  • position -- char
  • hardware_version -- uint8[3]
  • firmware_version -- uint8[3]
  • device_identifier -- uint16

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c' or 'd'.

The device identifier numbers can be found here

Callbacks

BrickletLCD20x4.CALLBACK_BUTTON_PRESSED
Function ID:

9

Response:
  • button -- uint8

This callback is triggered when a button is pressed. The response value is the number of the button (0 to 2 or 0 to 3 since hardware version 1.2).

BrickletLCD20x4.CALLBACK_BUTTON_RELEASED
Function ID:

10

Response:
  • button -- uint8

This callback is triggered when a button is released. The response value is the number of the button (0 to 2 or 0 to 3 since hardware version 1.2).