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3. INPUT DEVICES
3.1 Introduction
This
chapter
describes
some
pointing devices, keyboards
and
modems for a CD-i player.
The most important items
will
be discussed for each device.
• Data rate.
• Data flow.
• Data format.
3.2 Device Identification
3.2.1 Name convention
For identification
of pointing devices, keyboards and modems,
there
are
only
two
signals which will carry data.
ATS
~
~
CD-i
Input
player
Device
RXD
~
TXD
~
The first is the RTS
signal and
is
always
an output for the CD-i
player.
The
second
is the RXD
signal
and is always
an
input for
the CD-i player.
• RXD
:
carries
the data from pointing device, keyboard
or
modem to
player.
• RTS
: is used
for
device identification.
To identify the input device that is
connected
to the CD-i player,
each
input device
will
transmit its
own
device
(ID)
byte
on
request
or after
power
on.
3.2.2 Device ID sequence
1
Negate
RTS:
Current
data transmission to the CD-i player is
stopped.
2
Assert RTS.
3 The device
will send
its 1 byte device ID.
4 Sending a
complete
data packet is recommended
after
the
identification byte to determine the state
of
the buttons
at
start-up
.
NOTE
- The CD-i keyboard
sends
its 1 byte device ID,
and
clears its
buffer.
- Data transmission to the
CD-i
player
can
continue.
The
8
first byte
sent
to the CD-i player
should
be the header byte of
the device
data
packet (the first byte of a data packet d7
=
1).
3.2.3 Device ID codes
d6 d5 d4 d3 d2 dl dO
Mouse
I
Trackerball: 1
0
0
1
1
0
1
= ascii
char.'M' (Ox4D)
Joystick:
1
0
0
1
0
1
0
=
ascii
char. ']' (Ox4A)
Graph.tab .: 1
0
1
0
1
0
0
=
ascii char.
'T' (Ox54)
Touch
scr.
:
1
0
1
0
0
1
1
=
ascii char.
'S' (Ox53)
Modem
:
0
1
1
0
0
0
0
=
ascii
char.
'O'
(Ox30)
Ext.keyb.*: 1
0
0
1
0
1
1
=
ascii char
'K'
(Ox4B)
keyboard*: 1
0
1
1
0
0
0 =
ascii
char
'X'
(Ox58)
•
=
CDi-Keyboards
3.2.4 Device ID timing
CD-iPow~
~
CD-iRT~
~
Input Device TXD
1-rm
lliD
;J1W
A
A:
device power-on to ID byte timing:
Min. lOOms
Max. 500ms.
B:
negate RTS time:
Min.
lOms
Max.
irrelevant.
C
D
C:
Continued data transmission time
when
RTS is negated:
Min. Oms
Max. 1 byte time (1200 baud
=
8.3ms, 9600 baud
=
lms).
D: assert RTS to ID byte timing
when
device
is
powered:
Min. 1 bit time (1200 baud= 0.8 ms, 9600 baud= 0.1 ms).
Max.
10 ms.
NOTE
-
Using the optional key disk an extended (max. 1.2 sec.)
power-on to ID byte timing can be realised.
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