Pololu 0J5840 Скачать руководство пользователя

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1. Calling

pololu_3pi_init

(2000) to set up the 3pi, with the sensor timeout set to 2000×0.4 us

= 800 us. This means that the sensor values will vary from 0 (completely white) to 2000
(completely black), where a value of 2000 indicates that the sensor’s capacitor took at least
800 us to discharge.

2. Displaying the battery voltage returned by the

read_battery_millivolts()

function. It is

important to monitor battery voltage so that your robot does not surprisingly run out of
batteries and shut down during the middle of a competition or during programming. For more
information, see

Section 2

of the

command reference

[https://www.pololu.com/docs/0J18]

3. Calibrating the sensors. This is accomplished by turning the 3pi to the right and left on the line

while calling the

calibrate_line_sensors()

function. The minimum and maximum values read

during this time are stored in RAM. This allows the

read_line_sensors_calibrated()

function

to return values that are adjusted to range from 0 to 1000 for each sensor, even if some of
your sensors respond differently than the others. The

read_line()

function used later in the

code also depends on having calibrated values. For more information, see

Section 19

of the

command reference

[https://www.pololu.com/docs/0J18]

4. Displaying the calibrated line sensor values in a bar graph. This demonstrates the use of

the

lcd_load_custom_character()

function together with

print_character()

to make it easy

to see whether the line sensors are working properly before starting the robot. For more
information on this and other LCD commands, see

Section 5

of the

command reference

[https://www.pololu.com/docs/0J18]

5. Waiting for the user to press a button. It’s very important for your robot not to start driving

until you want it to start, or it could unexpectedly drive off of a table or out of your hands when
you are trying to program it. We use the

button_is_pressed()

function to wait for you to press

the B button while displaying the battery voltage or sensor readings. For more information
on button commands, see

Section 9

of the

command reference

[https://www.pololu.com/docs/

0J18]

In the second phase of the program, your 3pi will take a sensor reading and set the motor speed
appropriately based on the reading. The general idea is that if the robot is off on either side, it should
turn to get back on, but if it’s on the line, it should try to drive straight ahead. The following steps occur
inside of a

while(1)

loop, which will continue repeating over and over until the robot is turned off or

reset.

1. The function

read_line()

is called. This takes a sensor reading and returns an estimate of

the robot’s position with respect to the line, as a number between 0 and 4000. A value of
0 means that the line is to the left of sensor 0, value of 1000 means that the line is directly
under sensor 1, 2000 means that the line is directly under sensor 2, and so on.

2. The value returned by

read_line()

is divided into three possible cases:

Pololu 3pi Robot User’s Guide

7. Example Project #1: Line Following

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