I2c lcd protocol - Revision history

Rew: /* outdated */

2013-07-04T15:43:17Z

outdated

Rew at 15:43, 4 July 2013

2013-07-04T15:43:05Z

Rew: /* read identification */

2012-04-06T14:14:18Z

read identification

Rew: /* set cursor position */

2012-04-06T14:11:44Z

set cursor position

Rew: /* set cursor position */

2012-04-06T14:11:32Z

set cursor position

Rew: Created page with " The addresses on the I2C bus are 7 bits wide. The lower bit specifies if the transaction is to be a read or a write. Write transactions have the lower bit cleared (0), read t..."

2012-04-06T14:08:29Z

Created page with " The addresses on the I2C bus are 7 bits wide. The lower bit specifies if the transaction is to be a read or a write. Write transactions have the lower bit cleared (0), read t..."

New page

The addresses on the I2C bus are 7 bits wide. The lower bit specifies if the transaction is to be a read or a write. Write transactions have the lower bit cleared (0), read transactions have the lower bit set (1).

Each transaction on the I2C bus starts with the address of the board. The i2c_lcd board will ignore any transactions on the I2C bus that do not start with its own address.

After the address a single byte indicates the "port" on the board that the data is written to. The software can thus define 256 ports on each board.

Also see the [[general I2C protocol]]

= write ports =

Some ports just set a single value. So writing more than one byte to such a port is redundant. Other ports are logically a stream of bytes. So writing more than one byte is encouraged.

The spi_lcd board defines several ports.
{| border=1
! port !! function
|-
| 0x00 || display data.
|-
| 0x01 || write data as command to LCD.
|-
| 0x10 || any data clears the screen.
|-
| 0x11 || move the cursor to line l, position p. <br>l is the top 3 bits<br>p is the bottom 5 bits of the data.
|-
| 0x12 || set contrast.
|-
| 0x13 || set backlight.
|-
| 0xf0 || change address.
|}

= read ports =
The i2c_lcd board supports two read ports:

{| border=1
! port !! function
|-
| 0x01 || identification string. (terminated with 0).
|-
| 0x02 || read eeprom (serial number).
|}
= examples =

== read identification ==

read the identification string of the board. ('i2c_lcd 1.4').
{| border=1
! data sent !! explanation
|-
| START || create a START condition on the bus.
|-
| 0x82 || select destination with address 0x82 for WRITE.
|-
| 0x01 || identify port
|-
| STOP || create a STOP condition on the bus.
|-|-
| START || create a START condition on the bus.
|-
| 0x82 || select destination with address 0x82 for READ
|-
| 0x69 || 'i'
|-
| 0x32 || '2'
|-
| 0x63 || 'c'
|-
| ... || etc.
|}

== Send text to display ==
Display the string "Hello World!" (only the first 5 bytes of the string shown).
{| border=1
! data sent || explanation
|-
| START || create a START condition on the bus.
|-
| 0x82 || select destination with address 0x82 for WRITE
|-
| 0x00 || datastream
|-
| 0x48 || 'H'
|-
| 0x65 || 'e'
|-
| 0x6c || 'l'
|-
| 0x6c || 'l'
|-
| 0x6f || 'o'
|-
| xx || etc.
|}

== set cursor position ==
move to line 1, character 5:
{| border=1
! data sent !! data recieved || explanation
|-
| 0x82 || xx || select destination with address 0x82 for WRITE
|-
| 0x11 || xx || port 0x11 = set cursor position.
|-
| 0x25 || xx || 0x25 = 001 00101 = line 1 position 5.
|}

@@ Line 2: / Line 2: @@
 = outdated =
-This page is outdated. Please use the [Lcd_protocol_1.6] page.
+This page is outdated. Please use the [[Lcd_protocol_1.6]] page.
 == ----- old info follows: ----- ==
@@ Line 15: / Line 15: @@
 Also see the [[general I2C protocol]]
 = write ports =

@@ Line 1: / Line 1: @@
+= outdated =
+This page is outdated. Please use the [Lcd_protocol_1.6] page.
+== ----- old info follows: ----- ==
 The addresses on the I2C bus are 7 bits wide. The lower bit specifies if the transaction is to be a read or a write. Write transactions have the lower bit cleared (0), read transactions have the lower bit set (1).

@@ Line 60: / Line 60: @@
 | START || create a START condition on the bus.
 |-
-| 0x82 || select destination with address 0x82 for READ
+| 0x83 || select destination with address 0x82 for READ
 |-
 | 0x69  || 'i'

@@ Line 98: / Line 98: @@
 move to line 1, character 5:
 {| border=1
-! data sent !! data recieved || explanation
+! data sent !!  explanation
 |-
 | START || create a START condition on the bus.

@@ Line 100: / Line 100: @@
 ! data sent !! data recieved || explanation
 |-
+| START || create a START condition on the bus.
-| 0x82 || xx || select destination with address 0x82 for WRITE
 |-
+| 0x82 || select destination with address 0x82 for WRITE
-| 0x11 || xx || port 0x11 = set cursor position.
+|-
+| 0x11 || port 0x11 = set cursor position.
+|-
+| 0x25 || 0x25 = 001 00101 = line 1 position 5.
+|-
+| STOP || create a STOP condition on the bus.
 |-
-| 0x25 || xx  || 0x25 = 001 00101 = line 1 position 5.
 |}