Файл: Advanced Robotics with the Toddler (Paralax, student guide, v1.3, 2004).pdf

Page 166 · Advanced Robotics with the Toddler

milliseconds. The BASIC Stamp makes it so easy to turn on or off LEDs that it probably still isn’t a big problem. What if you had to do some calculations before deciding to turn the LED on or off? And what if those calculations take 30 ms for each LED?

A Processor’s Got to Know its Own Limitations!

Actually the processor doesn’t care. But it sure helps a programmer to know them. Of course, one way to help in high-speed real time programming is to use a faster processor. But every processor has some limit. Often it isn’t price effective to just throw a faster processor at a job. Besides, where’s the fun in that? One key to getting the most of any given processor is to use some simple techniques (and sometimes not so simple techniques) to maximize the use of the performance that is there.

In this situation with the BASIC Stamp, more speed adds some help but it would really be nice to do more than one thing at a time.

Where’s Real Time in Toddler?

Toddler Program 6.2: Object Detection And Avoidance sensed the outside surroundings using Infrared headlights and decided to where to move accordingly. It responded rather slowly because the sensing was only done between discrete moves. Wouldn’t it be better to sense all the time during moves and respond immediately? As mentioned before, Toddler has a more difficult time dealing with sensor inputs because it is walking instead of rolling. In a rolling robot like Boe-Bot, you can back up or turn at any time. Toddler can’t. If both feet are on the ground, it may first have to lift a leg before trying to move. This adds complexity to the program compared to a roller, but it can still be done. Better yet, it adds some personality to your Toddler too.

In this experiment we will use the Toddler Toes and the infrared object detection circuit from prior experiments to demonstrate real-time programming on the Toddler.

Chapter #8: Real-Time Programming with Bumpers and Infrared · Page 167

ACTIVITY #1: BUILDING AND TESTING TODDLER TOES AND INFRARED CIRCUIT

Parts Required

(1)Piezoelectric speaker

(2)Shrink wrapped IR LEDs

(2)IR detectors

(1)Set of Toddler Toes (Parallax #27312, not included in this kit) Optional: (2) LEDs and (2) 220 ohm resistors for feedback purposes (misc) wires

Toddler Toes kit (#27312) is not included in the stock Toddler Kit (#27310 or #27311) because it would have raised the retail price, prohibiting more robot enthusiasts from purchasing the kit. You can make your own toes using common materials.

This is what is included in the Parallax Toddler Toes Kit (#27312):

Assembling the Toddler Twinkle Toes

Figure 8.1 shows the schematic for the experiment.

Bending the Wires: Bend the wire to match the outline of the bumper in Figure 8-2. You will need to use needle nose pliers to do this job.

The two curled ends need to make a 50% to 75% closed circle to keep from sliding off the screw. Try to keep the wire flat while making these bends. The distance from one of the curls to the outside bend is not to be exceeded. Follow the template exactly and the bumpers will not hit each other.

Chapter #8: Real-Time Programming with Bumpers and Infrared · Page 169

You have six wires with which to experiment. You only need two good bumpers so don’t worry if the first ones don’t come out quite right. And if you really destroy all of your wires you can call Parallax for a few more.

critical distance not to exceed

Figure 8-2: Wire bending template

Bend wire exactly as shown

Fine Tuning the Wire Tension: Put the 3/8” screw through the center hole of each Twinkle Toes and secure tightly with a nut on top.

Attach the bumper hook ends over the screw you just mounted in the center of each board. The beveled corner goes on the side with the LED. Slip the wire in-between the prongs (two-post header pins) at each end of the board.

The bumper should be touching the pin closest to the front of the board. When pressing the bumper from the front the wire will touch the pin farthest from the front of the board. The pressure should feel very light to trip the bumper and will need to be adjusted until it is lightly springy.

Figure 8-3 shows how to adjust the bumper wire to be less stiff. For a final adjustment, take the bumper off, adjust and retest the tension. Once both sides of the bumper trip with a soft bump, secure with the locking nut. Do not tighten on the wire; the wire needs to be able to move freely around the screw.

Page 170 · Advanced Robotics with the Toddler

Figure 8-4 and Figure 8-5 show the final installation of the Twinkle Toes.

Figure 8-4: Installed

Twinkle Toes

Chapter #8: Real-Time Programming with Bumpers and Infrared · Page 171

Figure 8-5: Twinkle Toes include the pushbutton resistors and bi-color LED.

Mounting Twinkle Toes Disconnect the tilt rods from the Toddler’s left foot (the same side as the power switch). Mount the Twinkle Toes with two 1/4” screws (the third hole is only used if the ankle is mounted to the inside which would block one of the holes).

Make sure the bumper does not extend past the inside edge of the foot. If it does bend the wire or make a new bumper. One way to find out if the bumper is going to touch the opposite foot is to run one of the early basic walking programs in this text.

Reattach the control rod to the foot then mount the right sensor the same way and make sure it also does not extend past the inside edge of the foot. Repeat for the right foot.

Connect the cables Connect the cables from the sensors to X2 and X3 of the Toddler Board making sure the black to black connection (B to B) is maintained.

Testing the Toddler Toes

Let’s test the Toddler Toes circuit before we proceed to do anything else.

Page 172 · Advanced Robotics with the Toddler

'-----[ Title ]-----------------------------------------------------------

'Toddler Program 8.1 Twinkle Toes Test.bs2

'This program tests twinkle toes bumpers

'{$STAMP BS2}

'{$PBASIC 2.5}

'-----[ Constants ]-------------------------------------------------------

GOTO Forward

BothOn:

DIRS = ctrlLEDs

OUTS = bothRed

PAUSE 200

GOTO Forward

Right:

DIRS = ctrlLEDs

OUTS = rightRed

PAUSE 200

GOTO Forward

Left:

DIRS = ctrlLEDs

OUTS = leftRed

PAUSE 200

GOTO Forward

Chapter #8: Real-Time Programming with Bumpers and Infrared · Page 173

Figure 8-6: Toddler Toes Debug Test. Pushing the bumper should result in a “0” on the I/O pin.

If the Toes are properly installed and wired then you will be able to activate them and view the status of each bumper in the Debug Terminal as shown in Figure 8-6. If it works then proceed. If it does not work then double-check your three-conductor wire connectors and the wiring. The Twinkle Toes should flash green unless you press a bumper, then you will see a green-red intermittent flash.

Testing the Toddler Toes and Infrared Object Detection Circuit Together

Now make sure the infrared emitters and detectors are plugged in the front of the Toddler board. Then, run the following program to test the two circuits together.

'-----[ Title ]-----------------------------------------------------------

'Toddler Program 8.2 Infrared and Twinkle Toes Test.bs2

'This program tests infrared sensors and twinkle toes bumpers together

'{$STAMP BS2}

'{$PBASIC 2.5}

'-----[ I/O Definitions ]-------------------------------------------------