Programming Jabber

Initialization and calibration

Whenever we need to talk to the RCX, some initialization is required via the ActiveX control. That’s the same whether we’re going to calibrate or poll for values. The setup_RCX() function takes a single argument—the identification of which connector the light sensor is connected to—and performs the initialization, which is described later in Section 9.2.3.8. The function returns a handle on the Win32::OLE object that represents the ActiveX control, which in turn represents the RCX via the IR tower:

my $rcx = &setup_RCX(SENSOR);

If the -l option is not specified, it means we’re going to be running calibration. So we call the calibrate() function to do this for us. We pass the RCX handle (in $rcx) so the calibration can run properly:

# Either calibrate if no parameters given, or
# run with the parameter given as -l, which will
# be taken as the pivot between coffee and no coffee
&calibrate($rcx) unless defined($opts{'l'});

As with the setup_RCX() function, calibrate() is described later.

Calibration mode will be terminated by ending the script with Ctrl-C, so the next thing we come across is the call to the function set_status(), which represents the first stage in the normal script mode; set_status() is used to determine the initial coffee status.

A value is retrieved by calling the ActiveX control’s Poll() function. (Table 9-2 lists the ActiveX control’s functions and properties used in this script.) We specify that we’re after a sensor value (the ...