Waddle Bot Unit 1 Lesson 3

If Statements


The IF statement is the most basic logic command that all other logical structure is based on. This gives our NXT the ability to make choices based off of data. In a basic IF statement, a conditional statement determines if a block of code is executed or not. If the statement is TRUE, the block is executed, if the statement is FALSE, the block is skipped. Let's look at an example:

View Sensor Values on NXT

It's important to note that the value for the "threshold" variable was not picked at random. That number was picked because we tested the different regions on the field for what value the sensor will output. The NXT provides menu options that allow you to see the current sensor value. Use the arrow buttons to change your selection and the orange button to pick the selected menu option.

Conditional Statements


Computer logic is based around the ability of a computer to compare integers. Even the most complex choice can be boiled down to being able to determining if one number is greater than, less than, or equal to another number. This behavior forces us to form our logical instructions in a way that can be answered through evaluating two numbers. The result of this evaluation is a Boolean.



Our third major data type is called a Boolean. This data type deals with logic and is based in the binary language at the heart of every computer. Binary is defined as something "composed of two pieces or parts". Booleans are the same as in it only has two states: True or False. A Boolean can not have any other value.

Sensor Value [ sLabel]


Motors and Sensors are very similar in robotC. They are both special variables that are used to interface with the attached devices. Where motors accept data inputs, sensors only output data. This sensor integer value represents a real world condition that the NXT is sensing. In order to act on that information, we have to interpret the data for the NXT. We will do that below in conditional statements. For now, let's look at the elements of the variable.

Sensor Configuration


If motors are the output of our programs, then sensors are the input. Sensors give the NXT the ability to become aware of the world around it. We can use this awareness to grant the NXT the intelligence to navigate a dynamically changing world.

As with motors, before we can use a sensor, we must first configure it. This is done using the same tool we used to setup the motors.

Waddle Bot Unit 1 Lesson 2

Phases of a program


With all programming languages, there is an inherent order that certain instructions should be performed in. This behavior dictates were certain types of instructions are placed in the program. By using a template, we can streamline the creation process and build a uniform framework that all of our programs follow. The first step is to identify generic regions based on the actions taken by the NXT. Let's break apart our sample code and see how it is organized:

motor [ sLabel ]