Humidity

Detailed Description

Humidity Sensor object implementation for LwM2M client using Wakaama

Warning

This feature is experimental!
This implements the LwM2M Humidity Sensor object (ID 3304) as specified in the LwM2M registry. This IPSO object should be used with a humidity sensor to report a humidity measurement. It also provides resources for minimum/maximum measured values and the minimum/maximum range that can be measured by the humidity sensor. An example measurement unit is relative humidity as a percentage.

The sensor value can be updated by the application using the lwm2m_object_humidity_update_value function, or polled when required if a callback is registered upon object instantiation via lwm2m_obj_humidity_args_t::read_cb.

To use this object add USEMODULE += wakaama_objects_humidity to the application Makefile.

Resources

For an XML description of the object see https://raw.githubusercontent.com/OpenMobileAlliance/lwm2m-registry/prod/version_history/3304-1_0.xml

This object is based on the IPSO Sensor base object, therefore it shares the same resources.

Usage

1. Initialize the LwM2M object with an initialized client pointer.

lwm2m_object_t *obj = lwm2m_object_humidity_init(&client_data);

1. Create a new instance of the object with a given configuration (lwm2m_obj_humidity_args_t). Here, you can decide the way of updating the sensor values: polling or pushing. In this case, we register a callback function that is called whenever the sensor value is read.

// callback function to read the sensor value
int _read_cb(void *arg, int16_t *value)
{
    (void)arg;
 
    // generate new value
    *value = 100;
 
    return 0;
}
 
// initialize an instance of humidity sensor object
const lwm2m_obj_humidity_args_t humidity_args = {
    .min_range_value = 0.0,
    .max_range_value = 100.0,
    .units = "RH",
    .units_len = sizeof("RH") - 1,
    .instance_id = 0,
    .read_cb = _read_cb,
    .read_cb_arg = NULL
};
 
int32_t res = lwm2m_object_humidity_instance_create(&humidity_args);
 
if (res < 0) {
    puts("Could not create humidity object instance");
}

1. You can now update the sensor values using the lwm2m_object_humidity_update_value function.

uint16_t instance_id = (uint16_t)res;
lwm2m_object_humidity_update_value(&client_data, instance_id, new_value);

Topics
	LwM2M Humidity Sensor object compile configurations

Files
file	humidity.h

Macros
#define	LWM2M_HUMIDITY_OBJECT_ID   3304
	LwM2M Humidity Sensor object ID.

Typedefs
typedef lwm2m_obj_ipso_base_sensor_args_t	lwm2m_obj_humidity_args_t
	Arguments for the creation of a Humidity Sensor object instance.

Functions
lwm2m_object_t *	lwm2m_object_humidity_init (lwm2m_client_data_t *client_data)
	Initialize the Humidity Sensor object handle.
int32_t	lwm2m_object_humidity_instance_create (const lwm2m_obj_humidity_args_t *args)
	Create a new Humidity Sensor instance.
void	lwm2m_object_humidity_update_value (const lwm2m_client_data_t *client_data, uint16_t instance_id, int16_t value)
	Update the value of the humidity sensor and trigger a notification to the observing servers, if any.

Macro Definition Documentation

LWM2M_HUMIDITY_OBJECT_ID

#define LWM2M_HUMIDITY_OBJECT_ID   3304

LwM2M Humidity Sensor object ID.

Definition at line 119 of file humidity.h.

Typedef Documentation

lwm2m_obj_humidity_args_t

typedef lwm2m_obj_ipso_base_sensor_args_t lwm2m_obj_humidity_args_t

Arguments for the creation of a Humidity Sensor object instance.

Definition at line 124 of file humidity.h.

Function Documentation

lwm2m_object_humidity_init()

lwm2m_object_t * lwm2m_object_humidity_init

(

lwm2m_client_data_t *

client_data

)

Initialize the Humidity Sensor object handle.

Parameters

[in]

client_data

Pointer to the LwM2M client data.

Returns

Pointer to the global handle of the Humidity Sensor object.

lwm2m_object_humidity_instance_create()

int32_t lwm2m_object_humidity_instance_create

(

const lwm2m_obj_humidity_args_t *

args

)

Create a new Humidity Sensor instance.

Parameters

[in]

args

Initialize structure with the parameter for the instance. Must not be NULL.

Returns

> 0 value representing the instance ID if the instance was created successfully.

<0 otherwise

lwm2m_object_humidity_update_value()

void lwm2m_object_humidity_update_value	(	const lwm2m_client_data_t *	client_data,
		uint16_t	instance_id,
		int16_t	value )

Update the value of the humidity sensor and trigger a notification to the observing servers, if any.

Parameters

[in]	client_data	Pointer to the LwM2M client.
[in]	instance_id	ID of the instance to update.
[in]	value	New value for the sensor.