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Bots / The Ultimate Palm Robot/ Mukhar & Johnson / 222880-6 / Chapter 8

208 The Ultimate Palm Robot

✖ unsigned char The unsigned char type represents an unsigned byte.
It has a range of 0 to 255.
✖ int The int type represents a signed integer comprised of 2 bytes.
It has a range of –32768 to 32767.
✖ unsigned int The unsigned int type represents an unsigned integer
comprised of 2 bytes. It has a range of 0 to 65535.
✖ string The string type is a fixed series of ASCII-encoded text characters.
Now we get to the main loop of the program. The first thing that occurs in
the loop is that the program calls the aA2D_ReadInt( ) function for each of the
three sensors. You can see that the function takes an argument that tells the
function which sensor to read. In the chase.tea program, the code uses symbolic
constants to refer to each of the sensors. The symbolic constants APPRK_IR1,
APPRK_IR2, and APPRK_IR3 are defined in the aPPRK.tea file.

while (1)
{
r1=aA2D_ReadInt(APPRK_IR1);
r2=aA2D_ReadInt(APPRK_IR2);
r3=aA2D_ReadInt(APPRK_IR3);

This is followed by code that sets the value of the variable b based on which
sensors detect an object. If one or more of the sensors detect an object, the
value of b will be OR’d with 1, 2, or 4, depending on which sensors detect an
object. If only a single sensor detects an object, b will have the value 1, 2, or 4.
If more than one sensor detects an object, b will have the value 3, 5, 6, or 7. If no
sensor detects an object, none of the if statements will evaluate to true and b
will remain 0.

b=0;
if (r1>DRANGE) b = b | 1;
if (r2>DRANGE) b = b | 2;
if (r3>DRANGE) b = b | 4;
The code then executes a switch statement based on the value of b. If b is 1, 2,
or 4, the program commands the servos so that the robot moves toward the de-
tected object. If b is any other value, the default block executes and sets b to 0.

P:\010Comp\Bots\880-6\ch08.vp
Monday, May 12, 2003 1:16:45 PM