RobotC Frequently Used Commands (NXT)


Motors
Basic motor control commands, plus some fine-tuning commands.

motor[output] = power;
NXT

Turn the referenced NXT motor output either on or off and also sets the power level of the motor outputs.

The NXT has 3 motor outputs: motorA, motorB, motorC

The NXT can handle power levels from -100 (full reverse) to 100 (full forward). A power level of 0 will cause the motors to stop.

	motor[motorA] = 100;  //Output A - full speed forward
	motor[motorB] = 100;  //Output B - full speed forward

bMotorFlippedMode[output] = 1 or 0;
NXT

This feature is used to reverse the direction the referenced motor travels. Once this setting is changed, the reference motor will be reversed for the entire program (unless manually changed a later point in the program)

This is useful for when working with motors that mounted in different directions and the programmer wants to keep the power setting the same for both motors.

There are two settings: 0 - normal, 1 - reversed

Before:

	motor[motorA] = -100;  //Output A - full speed reverse
	motor[motorB] = 100;   //Output B - full speed forward

After:

	bMotorFlippedMode[motorA] = 1; //Motor Direction Flipped
	motor[motorA] = 100;           //Output A - full speed reverse
	motor[motorB] = 100;           //Output B - full speed forward

bFloatDuringInactiveMotorPWM = true or false;
NXT

This switch is used to choose wether the motors on the NXT will float or brake when there is no power applied. By default, the motors will float.

The reason to switch this is if you're trying to make precise turns with the NXT and the motors are drifting causing the change in direction to be off.

There are two settings for this switch:
false - motors will brake when inactive
true - motors will float when inactive

	bFloatDuringInactiveMotorPWM = false; //motors will brake when power is set to "0"

Timers
The NXT allows you to use Wait commands to place delays in your program. It also supports Timers, which work like stopwatches - they count time since the last reset, and you reset them again when you want to start or restart.

wait1Msec(wait_time);
NXT

This function will cause a program to wait a specified number of milliseconds before executing the next instruction in a program.

Wait_time is an integer (1 = 1/1000th of a second). Maximum wait time is 32.768 seconds when using this function.

	motor[motorA] = 100;  //Output A - full speed forward
	wait1Msec(2000);      //Wait 2 seconds
	motor[motorA] = 0;    //Output A - off

wait10Msec(wait_time);
NXT

This function will cause a program to wait a specified number of hundredths of a second before executing the next instruction in a program.

Wait_time is an integer (1 = 1/100th of a second). Maximum wait time is 327.68 seconds when using this function.

	motor[motorA] = 100;  //Output A - full speed forward
	wait10Msec(200);      //Wait 2 seconds
	motor[motorA] = 0;    //Output A - off

time1[timer] = time;
NXT

This timer function returns the current value of the referenced timer as an integer in a specific resolution. The resolution for "time10" is in milliseconds (1 = 1/1000th of a second).

The maximum amount of time to be recorded is 32.768 seconds (~1/2 minute)

The NXT has 4 internal timers: T1, T2, T3, T4

	int x;  //Init variable x
	x = time1[T1];  //assign variable x value of Timer #1 (1/1000th seconds)

time10[timer] = time;
NXT

This timer function returns the current value of the referenced timer as an integer in a specific resolution. The resolution for "time10" is in hundredths of a second (1 = 1/100th of a second).

The maximum amount of time to be recorded is 327.68 seconds (~5 minutes)

The NXT has 4 internal timers: T1, T2, T3, T4

	int x;  //Init variable x
	x = time10[T1];  //assign variable x value of Timer #1 (1/100th seconds)

time100[timer] = time;
NXT

This timer function returns the current value of the referenced timer as an integer in a specific resolution. The resolution for "time100" is in tenths of a second (1 = 1/10th of a second).

The maximum amount of time to be recorded is 3276.8 seconds (~54 minutes)

The NXT has 4 internal timers: T1, T2, T3, T4

	int x;  //Init variable x
	x = time100[T1];  //assign variable x value of Timer #1 (1/10th seconds)

ClearTimer(timer);
NXT

Resets the referenced timer back to zero seconds.

The NXT has 4 internal timers: T1, T2, T3, T4

	ClearTimer(T1);  //Clear Timer #1

Sensors
Sensor commands for configuration and usage are listed below. Most sensor setup should be done through the Robot > Motors and Sensors Setup menu for best results.

SetSensorType(sensor_input,sensor_type);
NXT

This function is used to manually set the mode of a specific input port to a specific type of sensor. We recommend, however, that you use the "Motor and Sensors Setup" wizard in RobotC.

The NXT has 4 sensor inputs: S1, S2, S3, S4

The NXT supports 8 different types of sensors:

Sensor Type
Type
Description
Range of Values
sensorTouch

RCX Sensor &
NXT Sensor

Digital 0 to 1
sensorTemperature RCX Sensor Analog, Temperature 0.0 to 100.0
sensorReflection RCX Sensor Analog, Percentage 0 to 100
sensorRotation RCX Sensor Digital with Directional Counter -32768 to 32768
sensorLightActive NXT Sensor Analog, Percentage
( Light Sensor with LED)
0 to 100
sensorLightInactive NXT Sensor

Analog, Percentage
(Light Sensor w/out LED)

0 to 100
sensorSoundDB NXT Sensor Analog, Percentage 0 to 100
sensorSONAR NXT only Distance, CM 0 to 255
   SetSensorType(S1, sensorTouch);  //Input 1 now is set to be a Touch Sensor

SensorValue(sensor_input)
NXT

SensorValue is used to read the value of the referenced sensor port. Values will correspond to the type of sensor set for that port (see set_sensor_type page).

The SensorValue function can be accessed like a variable, as it returns an integer value.

The NXT has 3 sensor inputs: S1, S2, S3, S4

	SetSensorType(S1, sensorTouch);  //Input 1 now is set to be a Touch Sensor
	
	if(SensorValue(S1) == 1)
	{
		motor[motorA] = 100;  //Output A - full speed forward
	}

nMotorEncoder[motor]
NXT

This function is used to access the internal encoder from the NXT's motors.

A value is return with the number of degrees the motor has traveled (1 = 1 degree), with the value as an integer.

	while(nMotorEncoder[motorA] < 1000) //while the encoder of MotorA is less than 1000 "counts"
	{
	  motor[motorA] = 100;           //Output A - full speed forward
	  motor[motorB] = 100;           //Output B - full speed forward
	}

You can also assign the value of nMotorEncoder to 0 to reset the encoder.

To reset the encoder on MotorA, use the following code:

	nMotorEncoder[MotorA] = 0;

ClearSensorValue(sensor_input)
NXT

This function is used to reset the value of the referenced sensor port back to zero. This is only neccessary with specific sensor types that retain their values (e.g. Encoder Sensor).

The NXT has 4 sensor inputs: S1, S2, S3, S4

	SetSensorType(S1, sensorRotation);  //Input #1 now is set to be a Rotation Sensor
	ClearSensorValue(S1); //Reset Input #1 back to a value of 0

Sounds
The NXT can generate tones, or play back stored waveform sound data.

PlayTone(frequency, duration)
NXT

Plays a sound from the NXT internal speaker at a specific frequency (1 = 1 hertz) for a specific length (1 = 1/100th of a second).

	PlayTone(220, 500);  //Plays a 220hz tone for 1/2 second

PlaySound(sound_name);
NXT

Plays a sound effect from the NXT internal library. Requires a sound name to be passed to play the sound.

Sound Names
soundBlip
soundBeepBeep
soundDownwardTones
soundUpwardTones
soundLowBuzz
soundFastUpwardTones
soundShortBlip
soundException
	PlaySound(soundUpwardTones);  //Plays the sound "Upward Tones"

PlaySoundFile(file_name);
NXT

This function is used to play a sound file that is on the NXT. NXT sounds files have the extension .rso.

	PlaySoundFile(Whoops.rso);  //Plays the sound file "Woops.rso" 

LCD Display
Commands for the NXT's LCD Display.

nxtDisplayTextLine(line_number, text, var1, var2, var3);
NXT

Displays a text line on the LCD screen of the NXT. Up to three variables are passable to the function.

line_number - The line the text line will appear on the NXT. There are 8 lines of text avaiable to the users, and valid arguments for this parameter are 0-7, which correspond to lines 1-8 on thte NXT's screen.

text - The text parameter is what shows up on the screen. This will be a string enclosed in quotes up to 16 characters. You may also display variables with this parameter by using the "%d" to display a variable definined in later parameters. You may use up to 3 "%d" characters to display 3 seperate variables. Remeber that you can only display 16 total characters, so the value of the variables will take up some of those 16 characters.

var1, var2, var3 = These parameters define which variables will be displayed to the screen.

    int x = 1; //declare first variable
    int y = 2; //declare second variable
    int z = 3; //declare third variable
   
	nxtDisplayTextLine(0,"Test %d %d %d",x,y,z);  
    //layout to display the text "Test 1 2 3" on the first line of the NXT screen

eraseDisplay();
NXT

Clears the NXT's LCD screen of all text and GUI images.

   eraseDisplay();

Miscellaneous
Miscellaneous useful commands that are not part of the standard C language.

random(value);
NXT

Returns a random number (integer) between 0 and the 'value' of the function.

	int x;  //declares x as an integer 
	x = random(100); //Returns a random value between 0 and 100