Hints For Software Development; Transmitting The First Command; Checking The Handshake Signals; Echo Mode Off - Logitech Magellan/SPACE MOUSE Classic Programmer's Manual

Hints for Software Development

The following hints should be helpful for
developing software using Magellan/SPACE
MOUSE.

Transmitting the First Command

After receiving the first valid 3D command via
the serial port (9600 Baud, 8 data bits, 2 stop
bits), the Magellan/SPACE MOUSE is in the 3D
mode with a data transmission rate of 9600
Baud. All errors received on the serial port
should be ignored until a valid byte is
transmitted to the Magellan/SPACE MOUSE.

Checking the Handshake Signals

Never transmit more than five bytes to
Magellan/SPACE MOUSE without checking the
handshake signal (CTS) status. Loss of data
and maladjustments of the Magellan/SPACE
MOUSE may occur if more than five bytes are
transmitted without checking the status.

Echo Mode OFF

Some computers retransmit received
characters (echo mode). This feature must be
turned off when using the Magellan/SPACE
MOUSE. If echo mode is not turned off, more
than five characters might be transmitted to
the Magellan/SPACE MOUSE without checking
the handshake signal status. In addition,
Magellan/SPACE MOUSE will erroneously
interpret each echo as a command.

Carriage Return Character "\r"

The commands transmitted to Magellan/SPACE
MOUSE must be terminated by the carriage
return character "\r" ("\r" = CR = 13d = 0DH).
If this character is missing at the end of a
command string, the Magellan/SPACE MOUSE
will remain in a completely passive state while
waiting for the terminating "\r". During this
time no displacements of the cap or keyboard
commands will be registered. If the Magellan/
SPACE MOUSE is fully passive and does not
react to displacements of the cap or keyboard
commands, it indicates the transmission of an
erroneous command without a terminating "\r"
character. (Keyboard commands always lead
to reactions of the Magellan/SPACE MOUSE
unless a command without a terminating "\r"
character is received. However, reactions to
displacements of the Magellan/SPACE MOUSE
cap are transmitted only if the translation and
rotation are in the ON state.)
Fixed Number of Characters in
Commands
All Magellan/SPACE MOUSE commands use a
fixed number of characters. Transmitting a
command with fewer characters to the
Magellan/SPACE MOUSE causes the device to
wait for the terminating "\r" character. After
each correctly received and interpreted
command, the Magellan/SPACE MOUSE returns
a well-defined response to the computer,
allowing the computer to check whether the
command was correctly interpreted.
10