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5.10.2 LCD Special mode function

The LCD special mode function supports display

modules that are compatible with the HD44780

controller and several graphic display controllers

that use a compatible interface . This controller is

made by Hitachi and has set the de-facto standard

for alphanumeric LCD modules.

The modules come in various configurations with

up to 80 characters total in any kind of

arrangement from single line to four lines.

Displays with more than 80 characters typically

use more than one HD44780. IO-Warrior does not

directly support modules with more than a single

HD44780, some additional hardware is required

for this.

It is recommended to read the HD44780 manual

for using the LCD function. Also have a look at

our application note AN5: Driving Display

Modules with IO-Warrior.

The LCD function is enabled by sending an output

report with ID 4 to the USB interface 1:

enable = $00 disables the LCD function. enable =

$01 enables the LCD function, other values are

reserved.

Upon enabling the LCD function the Pins are put

under control of the LCD function and can no

longer be controlled by SetReport to interface 0.

The /On pin is pulled low when the LCD function

is enabled, it will go high when the IO-Warrior

enters suspend state.

IOW24 does not allow to use SPI and LCD at the

same time. If SPI is enabled at the time a command

to enable LCD is received the command is ignored.

This means none of the LCD commands will be

executed when received nor will they send any

response. IOW24 will acknowledge that it received

the report with the command but not execute the

corresponding function and not send any reports in

reaction to the command.

To write data to the connected LCD module an

output report with ReportID 5 is written with the

following format:

"flags" contains the following bits:

7 - RS, Register Select bit

6 - unused, zero

5 - unused, zero

4 - unused, zero

3 - unused, zero

2 - data count MSB

1 - data count

0 - data count LSB

The status of the RS bit is used to set the RS line to

the LCD module. This allows access to the

Instruction register (RS=0) or Data Register (RS=

1) of the LCD module.

With "data count" the number of bytes to be

written is specified. IO-Warrior will write up to six

data bytes to the register specified by the RS bit.

The Busy bit of the LCD module is automatically

checked and data written only when the LCD

module is ready to accept it.

To read data from the LCD module an output

report with ID 6 is sent to interface 1:

"flags" contains the following bits:

7 - RS, Register Select bit

6 - unused, zero

5 - data count MSB

4 - data count

3 - data count

2 - data count

1 - data count

0 - data count LSB

RS specifies which register is to be accessed. Data

count sets the number of bytes to be read off the

LCD (will be ignored if RS=0, only a single read

will be done then).

Up to 63 bytes can be read with one request. The

data read from the LCD module is returned in input

reports with ID 6:

"count" specifies the number of bytes returned in

this report. If more than 6 bytes are requested the

data will be returned in multiple reports.

With chip revision 1.0.3.0 a 16ms timeout for the

Busy bit of the LCD has been added.

ReportID

$04 out

enable $00

$00 $00

$00

ReportID

$05 out

flags data

data data

data

ReportID

$06 out

flags $00

$00 $00

$00

ReportID

$06 in

count data

data data

data

V 1.1.0, December 2nd 2013, for chip revision V1.0.3.0 and up