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Chapter 4: Boe-Bot Navigation · Page 157

SUMMARY

This chapter introduced the basic Boe-Bot maneuvers: forward, backward, rotating in

place to turn to the right or left, and pivoting. The type of maneuver is determined by the

PULSOUT commands’ Duration arguments. How far the maneuver goes is determined

by the

FOR…NEXT loop’s StartValue and EndValue arguments.

Chapter 2 included a hardware adjustment, physically centering the Boe-Bot’s servos

with a screwdriver. This chapter focused on fine tuning adjustments made by

manipulating the software. Specifically, a difference in rotation speed between the two

servos was compensated for by changing the

PULSOUT command’s Duration argument

for the faster of the two servos. This changes the Boe-Bot’s path from a curve to a

straight line if the servos are not perfectly matched. To refine turning so that the Boe-Bot

turns to the desired angle, the

StartValue and EndValue arguments of a FOR…NEXT loop

can be adjusted.

Programming the Boe-Bot to travel a pre-defined distance can be accomplished by

measuring the distance it travels in one second, with the help of a ruler. Using this

distance, and the number of pulses in one second of run time, you can calculate the

number of pulses required to cover a desired distance.

Ramping was introduced as a way to gradually accelerate and decelerate. It’s kinder to

the servos, and we recommended that you use your own ramping routines in place of the

abrupt start and stop routines shown in the example programs. Ramping is accomplished

by taking the same variable that’s used as the

Counter argument in a FOR…NEXT loop and

adding it to or subtracting it from 750 in the

PULSOUT command’s Duration argument.

Subroutines were introduced as a way to make pre-programmed maneuvers reusable by a

PBASIC program. Instead of writing an entire

FOR…NEXT loop for each new maneuver, a

single subroutine that contains a

FOR…NEXT loop can be executed as needed with the

GOSUB command. A subroutine begins with a label, and ends with the RETURN command.

A subroutine is called from the main program with a

GOSUB command. When the

subroutine is finished and it encounters the

RETURN command, the next command to be

executed is the one immediately following the

GOSUB command.

Parallax Boe-Bot User Manual

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