RECORD AND PLAYBACK in Font

Printer Data Matrix ECC200 in Font RECORD AND PLAYBACK

Figure 5-3. First, choose the Record option in the Action section. Next, we need to specify a name for the recorded movement. As an example, I want SPOT to move forward two feet (motors B and C will be spinning forward) and turn left. I then want motor A to spin the propeller a few times. I m going to type the words Takeoff in the Name text box, shown in Figure 5-4, but you can type whatever description you like that will help you remember the purpose of the recorded movement.

Figure 5-4. Give your recorded movement a unique name. The name you type in the Name text box is the name of a file that will be stored on the Brick. This file must be stored on the Brick in order for you to later play back the movement, so try to make the name memorable and easy to understand. Now, look at Figure 5-5. The Recording section of the configuration panel is where you will specify which ports should be monitored. In my example, motors B and C will move my robot around, and motor A will spin the propeller. So I want to select all the ports. If you are not using one of the motor ports, you don t need to select it. You won t get an error if you select a motor port and don t use it, however.

Figure 5-5. Configure the motor ports to monitor and record. The last item you will need to configure is the amount of time (in seconds) you wish to record your bot s movements (see Figure 5-6). You can type in the number of seconds you want to record or click the up and down arrows with your mouse to select the number in the Time section.

Figure 5-6. Enter the number of seconds to record in the Time section. You can record anywhere from one second up into the hundreds of minutes. Is this realistic Not really. Your NXT Brick has a limited amount of memory, and you ll find that you are limited to a few minutes at most. And even recording a few minutes of movement will probably not leave much memory for your actual program. You ll have to play around with the Time section to test its limits.

Once you ve got your RECORD/PLAY block configured, save the program, and upload it to your NXT bot. Place the robot at its starting position, and press the Run button for your new program. Using your hands, guide the robot through the movements you wish your robot to perform.

For my example, I simply push the robot forward two feet and stop. I then turn the robot to the left and stop. Next, I spin the little propeller on the front of the robot five or six times, and I m finished. I suggest that you time your movements as you re doing them. If you come close to the number of seconds you configured, you can simply leave the recording time alone. If you didn t have enough time, go back and add the right number of seconds to your program, save it, and run it again to record the complete movements. Most importantly, if you originally configured too much time, reduce the number of seconds you entered in the Time section; because the recording process will continue to run until the time is over, the file stored on the Brick will be larger than it needs to be.

Okay, so you ve successfully recorded your bot s movements, and there is a file stored on the Brick with the name you gave it in the Name section (you can verify this by connecting your Brick to your computer and checking its memory contents). Now, let me show you how to play back the file. It s so easy, you re going to laugh. Create a new program, and drop in a RECORD/PLAY block. This time, however, select the Play option in the Action section (see Figure 5-7).

Note If you have your NXT Brick connected to your computer via the USB cable, any files stored on the NXT that

you created using the RECORD/PLAY block will appear in the File section seen in Figure 5-7. Rather than type the name of the file, you can select it from the list. If you do not have your NXT Brick connected, you will need to remember the name of the file and type it in the Name section.

Figure 5-7. Configure your robot to play back the recorded movement. The only other section that can be configured now is the Name section. Type the name of the file that contains the recorded movements in the Name section (see Figure 5-8). For my example, I ve typed Takeoff, the name I gave the file that moves the robot forward two feet, turns it left, and then spins the propeller a few times.