Page 208 - The Unofficial Guide to Lego Mindstorms Robots

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if (SENSOR_1 < 0xf000) {
// Touch sensor is pressed.
}

If you're working with light or rotation sen sors, legOS does offer some help. First, you can set inputs to be active or passive:

void ds_active(unsigned∗ const sensor)

void ds_passive(unsigned∗ const sensor)

Use these functions to set the specified sensor to active or passive mode. The light and rotation sensors are active sensors;
the touch and temperature sensors are passive.

T he argument to these functions is the address of one of the sensor values. For exa mple, to set input 2 to be active, you would
do this:

ds_active(&SENSOR_2);

Processed light sensor values can be retrieved with the following macros:

LIGHT_1

LIGHT_2

LIGHT_3

These macros process raw input values t o produce a light sensor reading in the range from 0 to approximately
LIGHT_MAX.

legOS also supports rotation sensors with the following functions:

void ds_rotation_ (unsigned∗ const sensor)
on

void ds_rotation_off(unsigned∗ const sensor)

These functions turn on or off rotation counting for the specified input.

void ds_rotation_set(unsigned∗ const sensor, int pos)

This function sets the current rotation count of the given input.

Once you get the input set up for rotation, you can retrieve the rotation value with one of the following macros:

ROTATION_1

ROTATION_2

ROTATION_3

These macros return the rotation count for each of the inputs.

Setting up input 3 for a rotation sensor, then, looks something like this:

ds_active(&SENSOR_3);
ds_rotation_on(&SENSOR_3);
ds_rotation_set(&SENSOR_3, 0);

To actually read the rotation value, you would just use the ROTATION_3 macro.