Page 135 - The Definitive Guide to Building Java Robots

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116 CHAPTER 4 ■ SENSORS

Now that you’re familiar with the hardware, I’ll create some software to get readings from
these using a BASIC Stamp. Afterward, I’ll create two Java classes.

Code Objective

The objective here is to get compass readings from a robot using one of the three compasses
described earlier.

Code Discussion
I’ll start with programming the BASIC Stamp. In the first part of this program (see Example 4-1),
I connect my three compasses to the different pins on the Stamp (1 and 2) for the Devantech,
(8, 9, 10, and 11) for the Vector, and (0, 1, 2, and 3) for the Dinsmore.
Second, I create my main program where I wait for specific commands: 100 to start reading,
101 for the Dinsmore, 102 for the Devantech, and 103 for the Vector.
Third, I create three separate subroutines for the different compasses. For the Devantech
compass, I just need to use the PULSIN to get the compass reading, For the Vector, I need to
send some signals and wait for a time before I can SHIFTIN the readings. And the Dinsmore
reads logic values from the input pins to return one of eight readings (N, E, S, W, NE, NW, SE,
SW). (See Figure 4-1.)

Example 4-1. Compass.bs2
' {$STAMP BS2}
' {$PBASIC 2.5}
' {$PORT COM1}
' cmd variable
cmd VAR Byte
N9600 CON 16468

' CMPS03 COMPASS
cin CON 12 'serial data out GREEN (a)
headingC VAR Word 'heading

' VECTOR COMPASS
sselect CON 10 'select signal
sdo CON 09 'serial data out
sclk CON 11 'clock signal
rst CON 8 'reset signal
headingV VAR Word 'heading

' DINSMORE 1490 COMPASS
north CON 0
east CON 1
south CON 2
west CON 3
headingD VAR Byte