Arduino LCD Display Protocol

This protocol controls a HD44780 LCD screen connected to the microcontroller. After the welcome message it has no events, but a huge variety of commands.

How to build a test circuit with a lcd display and an Arduino Mega?
Arduino codes are included.

I. "Welcome" event from microcontroller

Example

c=welcome&id=A47vvH&type=OzLcdController&pos=2&t=3

Parameters

Parameter Type Range Functionality
c String "welcome" Identifies the welcome message.
type String "OzLcdController" Determines the type of the device.
id String 6 characters (numbers, uppercase and lowercase characters) The ID of the device which is chosen by the microcontroller.
pos Byte 0-255 Determines the position of the device on the list of the ID manager of the microcontroller. Please make sure there are no other devices in the same position.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.


II. Commands to microcontroller

"Write" command

If the cursor is set in a position which is on the LCD sceen. Then this command writes out the message to the LCD screen.

Example

c=write&word=test&t=0&id=A47vvH

Parameters

Parameter Type Range Functionality
c String "write" Identifies the command.
word String Max. 30 chars The text itself, which will be displayed on the screen.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of commands sent. Counts from 0 to 255 then from 0 again.

Response

c=write_resp&row=1&column=4&word=test&id=A47vvH&t=3

Parameters

Parameter Type Range Functionality
c String "write_resp" Identifies the response.
row Byte 0-255 Number of rows.
column Byte 0-255 Number of columns.
word String Max. 30 chars The text itself, which will be displayed on the screen.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.


"Set Backlight" command

Changes LCD illumination to a selected value.

Example

c=setbacklight&value=60&t=1&id=A47vvH

Parameters

Parameter Type Range Functionality
c String "setbacklight" Identifies the command.
value Byte 0-100 (%) Changes the LCD illumination to a selected percentage value.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of commands sent. Counts from 0 to 255 then from 0 again.

Response

c=setbacklight_resp&value=60&id=A47vvH&t=4

Parameters

Parameter Type Range Functionality
c String "setdisplay_resp" Identifies the response.
value Byte 0-100 (%) Responds the value ordered by the command.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.


"Set Display" command

Turns on and off the LCD display.

Example

c=setdisplay&state=1&t=2&id=A47vvH

Parameters

Parameter Type Range Functionality
c String "setdisplay" Identifies the command.
state Bool 0,1 True turns display on, false turns display off.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of commands sent. Counts from 0 to 255 then from 0 again.

Response

c=setdisplay_resp&state=1&id=A47vvH&t=5

Parameters

Parameter Type Range Functionality
c String "setdisplay_resp" Identifies the response.
state Bool 0,1 Responds the state ordered by the command.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.


"Clear Display" command

Removes every character from the LCD screen. The ID identifies the screen.

Example

c=cleardisplay&t=3&id=A47vvH

Parameters

Parameter Type Range Functionality
c String "cleardisplay" Identifies the command.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of commands sent. Counts from 0 to 255 then from 0 again.

Response

c=cleardisplay_resp&id=A47vvH&t=6

Parameters

Parameter Type Range Functionality
c String "cleardisplay_resp" Identifies the response.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.


"Set Cursor" command

Turns on or off the small cursor. You can only write on the LCD if the cursor is set to one of the visible character positions.

Example

c=setcursor&state=1&t=4&id=A47vvH

Parameters

Parameter Type Range Functionality
c String "setcursor" Identifies the command.
state Bool 0,1 If true the cursor is set, if false there is no cursor.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of commands sent. Counts from 0 to 255 then from 0 again.

Response

c=setcursor_resp&state=1&id=A47vvH&t=7

Parameters

Parameter Type Range Functionality
c String "setcursor_resp" Identifies the response.
state Bool 0,1 Responds the state ordered by the command.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.


"Set Blink" command

Turns on or off the huge flashing cursor.

Example

c=setblink&state=1&t=5&id=A47vvH

Parameters

Parameter Type Range Functionality
c String "setblink" Identifies the command.
state Bool 0,1 True activates the huge blinking cursor. False deactivates it.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of commands sent. Counts from 0 to 255 then from 0 again.

Response

c=setblink_resp&state=1&id=A47vvH&t=8

Parameters

Parameter Type Range Functionality
c String "setblink_resp" Identifies the response.
state Bool 0,1 Responds the cursor state ordered by the command.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.


"Set Position" command

Set the position of the cursor. You can add the rows and the colums where you want start writing.

Example

c=setposition&row=1&column=1&t=6&id=A47vvH

Parameters

Parameter Type Range Functionality
c String "setposition" Identifies the command.
row Byte 0-255 Row number of the cursor position.
column Byte 0-255 Column number of the cursor position.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of commands sent. Counts from 0 to 255 then from 0 again.

Response

c=setposition_resp&row=1&column=1&id=A47vvH&t=9

Parameters

Parameter Type Range Functionality
c String "setposition_resp" Identifies the response.
row Byte 0-255 Row number of the cursor position.
column Byte 0-255 Column number of the cursor position.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.


"Autoscroll" command

If Autoscroll is set it and you reach the end of the LCD screen, it pulls up every row by one.

Example

c=setautoscroll&state=1&t=7&id=A47vvH

Parameters

Parameter Type Range Functionality
c String "setautoscroll" Identifies the command.
state Bool 0,1 True activates autscroll, false deactivates it.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of commands sent. Counts from 0 to 255 then from 0 again.

Response

c=setautoscroll_resp&state=1&id=A47vvH&t=10

Parameters

Parameter Type Range Functionality
c String "setautoscroll_resp" Identifies the response.
state Bool 0,1 Responds the state ordered by the command.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.


"Return Home" command

Sets the cursor to the first row's first character.

Example

c=returnhome&t=8&id=A47vvH

Parameters

Parameter Type Range Functionality
c String "returnhome" Identifies the command.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of commands sent. Counts from 0 to 255 then from 0 again.

Response

c=returnhome_resp&id=A47vvH&t=11

Parameters

Parameter Type Range Functionality
c String "returnhome_resp" Identifies the response.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.


III. Event from microcontroller

"Display Size" event

After the welcome event the device sends the LCD's size (rows and columns).

Example

c=displaysize&row=4&column=20&id=A47vvH&t=3

Parameters

Parameter Type Range Functionality
c String "displaysize" Identifies the event.
row Byte 0-255 Number of rows.
column Byte 0-255 Number of columns.
id String 6 characters (numbers, uppercase and lowercase characters) Identifies the device. The ID is never changed during communication.
t Byte 0-255 Counts the number of events and responses sent combined. Counts from 0 to 255 then from 0 again.

More information