Programming for light sensor input:
Like programming for
touch sensor input, the RCX has to have a program that can act on incoming
light sensor information. For example, if a program is set to run a certain
way if the sensor detects bright light, then the program must have a way of
monitoring changes in light levels.
RCX Code offers several ways to obtain light
sensor input, using Stack Decision Makers (red, orange, or purple blocks) and
Sensor Watchers (blue blocks).
Stack Decision Makers
are incorporated in a stack of commands, checking for sensor input when their
turn to run comes. The program then continues top-down, block after block. The
Wait Until block does what it says, it waits until a certain condition
is met. The Repeat While repeats a stack of commands while a certain
condition is met, and the Repeat Until does the same until a certain
condition is met.
Sensor Watchers also check for sensor input, but they are not
embedded in a stack of commands. They are connected to the program at the top
level (to the programís title block). At this level, Sensor Watchers monitor
the sensors all the time (with preset intervals), checking for input
repeatedly while other parts of the program continue to run. With Sensor
Watchers, a program can monitor up to nine sensor events.