In general, Contiki-NG adopts the C programming language.

Creating a Project

The Contiki-NG program does not provide project templates to build a program. If you want to create a new project, you start by creating a new folder and a Makefile file. Notice that we also can use program samples from the Contiki project.

Contiki-NG Basic Programming Language

Contiki-NG adopts the C general programming language for implementation. Contiki-NG programming is similar to C as far as declaring variables and using conditional statements and looping.

Declare variables -> Assign variables -> Looping -> If-conditional -> Comment codes

int alpha;
unsigned int beta;

alpha = 0;
beta = 0;

for(int i = 0; i < 10; i++)
{
 Looping();
 if(running){
  performSomethingA();
 }else {
  performSomethingB();
 }
}

/* Here comes a comment... */

Review of Protothreads

Protothreads are lightweight threads designed for memory-constrained systems, such as small embedded systems or WSN nodes. The implementations for Contiki-NG located in the <contiki_root>/os/sys/pt.h. The following is a list of function descriptions based on the pt.h header:

• PT_INIT(pt) function is used to initialize a protothread.
• PT_THREAD(name_args) is a macro that is used to declare a protothread.
• PT_BEGIN(pt) is used to declare the starting point of a protothread.
• PT_END(pt) is used to end a protothread.
• PT_WAIT_UNTIL(pt, condition) is used for blocking the protothread until the specified condition is true.
• PT_WAIT_WHILE(pt, cond) is used for blocking and waiting while the condition is true.
• PT_WAIT_THREAD(pt, thread) is used to schedule a child protothread. The current protothread will block until the child protothread completes.
• PT_SPAWN(pt, child, thread) is used to spawn a child protothread and waits until it exits.
• PT_RESTART(pt) will block and cause the running protothread to restart its execution at the place of the PT_BEGIN() call.
• PT_EXIT(pt) is used to exit from a protothread.
• PT_SCHEDULE(f) is used to schedule a protothread. The return value of the function is non-zero if the protothread is running or zero if the protothread has exited.
• PT_YIELD(pt) yields from the current protothread.
• PT_YIELD_UNTIL(pt, cond) yields from the protothread until a condition occurs.

Extending the Contiki-NG Library

Contiki-NG OS consists of several libraries and apps that can extend based for specific cases. To extend Contiki-NG OS functionalities, we can follow the same approach used while building C programs. We can add additional libraries by adding a C header and source code. Then, our Contiki-NG program will consume our libraries.

Sample Library

• sample.h - Define the header.

#ifndef SAMPLE
#define SAMPLE

int sample_counter(int current);

#endif

• sample.c - Implement the header.

#include "sample.h"

int sameple_counter(int current)
{ 
 if(current > 99)
  current = 1;
 else
  current += 1;
 return current;
}

• Next, we will implement our extended library and use it in a Contiki-NG program. To access the extended library, we declare that header file. Then, we call library functions from our code.

#include "mycounter.h"

...

static int counter = 0;
counter = next_counter(counter);
printf("Counter: %d\n", counter);