Page 143 - The Unofficial Guide to Lego Mindstorms Robots

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Table 6-8. Input Type Values (continued)

Value Description

3 Light sens or

4 Rotation sensor

SENSOR_MODE (mode index -- )
This word sets the mode of the given input. An input's mode determines how the sensor values will be interpreted. The modes
are shown in Table 6-9.

Table 6-9. Input Mode Values

Value (hex) Description

0 Raw sensor value from 0 to 1023

1
20 Boo lean, either or 0

40 Counts transitions from 1 to 0 and vice versa (e dge counting)

60 Counts transitions from 1 to 0 (pulse counting)

80 Percent from 0 to 100

A0 Celsius temperature

C 0 Fahrenheit temperature

E 0 Shaft angle, 16 counts per full revolution

The following example shows how you cou ld configure input 3 for a light sensor:

2 CONSTANT INPUT_3
ok
SENSOR_INIT
ok
INPUT_3 SENSOR_ACTIVE
ok
3 INPUT_3 SENSOR_TYPE
ok
80 INPUT_3 SENSOR_MODE
ok

Reading input values

Reading input values in pbFORTH is a two-step process. First, you need to tell pbFORTH to go and read the input values:
SENSOR_READ (index -- code)

This word tells pbFORTH to read the value of the specified input. The actual value can be retrieved with a call to
SENSOR_GET, which is described later. A status code is placed on the stack. If code is 0, then the read was successful.
Values other than 0 indicate that the RCX was busy and could not read the input value.