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Bots /The Ultimate Palm Robot/ Mukhar & Johnson / 222880-6 / Chapter 9

Chapter 9 Sensors and Enhancements 243

When attaching the Hamamatsu photoreflector to the SV203, the Vcc and
GND pins are attached to the Vcc and GND pins in block J4. The Vo pin is
attached to one of the A/D ports in block J3. This is the same way we attached
the IR rangers to the SV203. We recommend that you use a circuit board or
breadboard to mount the sensor. This will give you a way to attach the sensor
to the frame of the robot. For best operation, the sensor needs to be mounted
within just a few millimeters of the surface. The specification sheet that comes
withthesensorgivestheoperatingcharacteristicsat3mm.Thatisapproximately
1/8 inch. The sensor will work if it is slightly further away than the optimal
3mm, but its performance will be degraded.
Recall from Chapter 7 that we can read the analog port with the command
ADn, where n is the port number from 1 to 5. Thus, to use this sensor, you will
send the AD command to the board and read the output. If the sensor is in the
high state, you will receive a value of 255. When the sensor is in the low state,
you will receive a very low value (but not necessarily 0). Arepresentative code
listing to do this using HotPaw Basic is shown next. This code listing assumes
that the P5587 IR photoreflector is connected to port 1. You would need to
change the listing to reflect the actual port you use.

print #5, "BD1 AD1" : rem tell board sensor 1
result = get$(#5, 0) : rem read 1 byte
if (result < 50)
/* P5587 sensor is not over line */
else
/* P5587 sensor is over line */
endif

Connecting this sensor to the BrainStem is just as easy. Just as with the
SV203, you will connect the GND, Vcc, and Vo pins of the sensor to the correct
pins of the BrainStem.
After connecting the sensor to the BrainStem and mounting it to the robot
at approximately 3mm over the surface to be sensed, we can read its output
using the TEA language. Here is sample TEA code for the BrainStem that
assumes the IR photoreflector is connected to port 1.

r1=aA2D_ReadInt(APPRK_IR1);
if (r1<50) {

P:\010Comp\Bots\880-6\ch09.vp
Monday, May 12, 2003 4:33:41 PM