lesson-1.rst

Zephyr Behaviour Tree - Tutorial - Lesson 1

Implement the First Action

The first example how to implement the Grab Beer Action. The change is add a counter to make the action fail after some iterations. This simpler example can be easier translated to check some hardware condition like ADC's, actuators etc.

1- Add a new file at <project>/src/grab_beer.c

2- Add the following content

#include <stdint.h>
#include <zephyr/zephyrbt/zephyrbt.h>
#include <zephyr/sys/util.h>

#include <zephyr/logging/log.h>
LOG_MODULE_REGISTER(grab_beer, CONFIG_ZEPHYR_BEHAVIOUR_TREE_LOG_LEVEL);

enum zephyrbt_child_status
zephyrbt_action_grab_beer(struct zephyrbt_context *ctx,
         struct zephyrbt_node *self)
{
   static int count = 0;

   ++count;

   LOG_DBG("\nGrab Beer try: %d\n", count);

   if (count < 3) {
      return ZEPHYRBT_CHILD_SUCCESS_STATUS;
   }

   return ZEPHYRBT_CHILD_FAILURE_STATUS;
}

3- Update the CMakeLists.c

target_sources(app PRIVATE
   src/main.c
   src/grab_beer.c
)

4- Run the program again

$> west build - run

5- Compare the execution

At this time the initial output will be the same but after 3 iterations the system will grab the water as a fallback action.

You can explore more ideas and try to implement other actions to play with the application.