1. NXC (and NBC)
NXC (Not eXactly C) is a language similar to NQC, which was the most popular way to program the RCX
Built on NBC, the Next Byte Code ‘assembler’
Uses the built in firmware, and p-code system

2. NXC uses BricxCC Reasonably stable development environment
Provides support for all LEGO robotic platforms
Free!

3. Programming with NXC Assuming you are comfortable with C…
How to use the motors
How to read the sensors
Threading model

4. NXC Programs NXC is based on C
Restrictions because it’s based on the built-in P-Code system
There’s no stack
Limited memory
Limited number of tasks (256)
And subroutines, which are also ‘tasks’

5. NXC program skeleton
#include "NXCDefs.h"
task main() { }

6. NXC Sensors #include "NXCDefs.h" task main() {
SetSensorType( IN_1, SENSOR_TYPE_TOUCH );
SetSensorMode( IN_1, SENSOR_MODE_BOOL ); }

7. NXC Sensors #include "NXCDefs.h" task main() {
SetSensor( IN_1, SENSOR_TOUCH ); }

8. NXC Sensors
To read a sensor use x = Sensor( IN_1 );

9. NXC Sample program #include "NXCDefs.h“ task main() {
SetSensor( IN_1, SENSOR_TOUCH );
while( true ) {
if( Sensor( IN_1 ) ) {
PlayToneEx(440, 100, 3, false);
TextOut( 0, LCD_LINE1, "TOUCHING!");
while( Sensor( IN_1 ) ) ; }
TextOut( 0, LCD_LINE1, " ");
while( !Sensor( IN_1 ) )

10. NXC Motors Simple motor commands are available
OnFwd(), OnRev(), Off(), Float()

11. NXC Motors
To use the built-in rotation sensors, you need to use the new motor commands
Easiest to use is RotateMotor()

12. RotateMotor RotateMotor( port, speed, angle );
port is OUT_A, OUT_B, OUT_C, or combinations such as OUT_AB, OUT_ABC
speed is a number -100 to 100
angle is the number of degrees you want the motor to turn (positive or negative)

13. Mimicking a Servo Motor
Read the current motor angle
Current = MotorRotationCount( OUT_A );
Calculate how far you need to turn
Delta = Target – Current;
Turn that amount
RotateMotor( OUT_A, speed, Delta );

14. Displaying Text The LCD display is useful for Debugging
Setting parameters
Runtime messages
Graphics
Games
… and more

15. Displaying Text
TextOut( x, y, text );
NumOut( x, y, number );

16. LCD display The origin is the bottom left
So TextOut( 0,0, “hi” ) will display in the bottom left corner
Use the LCD_LINEn macros if you like to make it easier

17. Text Example y = 42; TextOut(0, LCD_LINE5, "Answer:" );
NumOut( 8*6, LCD_LINE5, y );
// characters are 6 pixels wide

18. Graphics
There are also commands to draw lines, circles, rectangles, and set points
You can display bitmaps from a file
RIC files – contain drawing commands
One problem is there isn’t an easy way to clear areas of the screen
It’s easy to clear the whole screen
You can display a 1x1 blank bitmap

19. Tasks and Subroutines
Multiple tasks are possible, but don’t work like you might expect
Scheduling is different – tasks start when a ‘dependant’ task finishes
There is no easy way of stopping a task
Use Precedes() or Follows() in a task to define task dependencies

20. Tasks task FooTask() { // will start executing when main() finishes }
task main() { // program starts here
Precedes( FooTask );
task BarTask() {
Follows( main );
// will also start executing when main() finishes

21. Subroutines Essentially a task that can be called
It suspends the calling task until it returns
Don’t use task keyword to define these
Can pass in parameters or return a value

22. Subroutine Example void TestSub( int x, int y, short i ) { x = y + i;}
task main()
TestSub( 1, 2, 3 );

23. NXC Help Preliminary help file is a PDF
There are many samples and a tutorial online