Voltage

Voltmeter object implementation for LwM2M client using Wakaama. More...

Detailed Description

Voltmeter object implementation for LwM2M client using Wakaama.

Warning

This feature is experimental!
This implements the LwM2M Voltage Sensor object (ID 3316) as specified in the LwM2M registry. This IPSO object should be used with voltmeter sensor to report measured voltage between two points. It also provides resources for minimum and maximum measured values, as well as the minimum and maximum range that can be measured by the sensor. An example measurement unit is volts.

The sensor value can be updated by the application using the lwm2m_object_voltage_update_value function, or polled when required if a callback is registered upon object instantiation via lwm2m_obj_voltage_args_t::read_cb.

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

Resources

For an XML description of the object see https://raw.githubusercontent.com/OpenMobileAlliance/lwm2m-registry/prod/version_history/3316-1_0.xml

This object is based on the IPSO Sensor base object, therefore it shares the same resources. Note that the optional resources "Current Calibration" (ID 5821) and "Application Type" (ID 5750) are not implemented.

Usage

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

lwm2m_object_t *obj = lwm2m_object_voltage_init(&client_data);

1. Create a new instance of the object with a given configuration (lwm2m_obj_voltage_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 voltage sensor object
const lwm2m_obj_voltage_args_t voltage_args = {
    .min_range_value = -50.0,
    .max_range_value = 200.0,
    .units = "V",
    .units_len = sizeof("V") - 1,
    .instance_id = 0,
    .read_cb = _read_cb,
    .read_cb_arg = NULL
};
 
int32_t res = lwm2m_object_voltage_instance_create(&voltage_args);
 
if (res < 0) {
    puts("Could not create voltage object instance");
}

1. You can now update the sensor values using the lwm2m_object_voltage_update_value function.

uint16_t instance_id = (uint16_t)res;
lwm2m_object_voltage_update_value(&client_data, instance_id, new_value);

Modules
	LwM2M Voltage Sensor object compile configurations

Files
file	voltage.h

Macros
#define	LWM2M_VOLTAGE_OBJECT_ID   3316
	LwM2M Voltage Sensor object ID.

Typedefs
typedef lwm2m_obj_ipso_base_sensor_args_t	lwm2m_obj_voltage_args_t
	Arguments for the creation of a Voltage Sensor object instance.

Functions
lwm2m_object_t *	lwm2m_object_voltage_init (lwm2m_client_data_t *client_data)
	Initialize the Voltage Sensor object handle.
int32_t	lwm2m_object_voltage_instance_create (const lwm2m_obj_voltage_args_t *args)
	Create a new Voltage Sensor instance.
void	lwm2m_object_voltage_update_value (const lwm2m_client_data_t *client_data, uint16_t instance_id, int16_t value)
	Update the value of the voltage sensor and trigger a notification to the observing servers, if any.

Macro Definition Documentation

LWM2M_VOLTAGE_OBJECT_ID

#define LWM2M_VOLTAGE_OBJECT_ID   3316

LwM2M Voltage Sensor object ID.

Definition at line 120 of file voltage.h.

Typedef Documentation

lwm2m_obj_voltage_args_t

typedef lwm2m_obj_ipso_base_sensor_args_t lwm2m_obj_voltage_args_t

Arguments for the creation of a Voltage Sensor object instance.

Definition at line 125 of file voltage.h.

Function Documentation

lwm2m_object_voltage_init()

lwm2m_object_t * lwm2m_object_voltage_init

(

lwm2m_client_data_t *

client_data

)

Initialize the Voltage Sensor object handle.

Parameters

[in]

client_data

Pointer to the LwM2M client data.

Returns

Pointer to the global handle of the Voltage Sensor object.

lwm2m_object_voltage_instance_create()

int32_t lwm2m_object_voltage_instance_create

(

const lwm2m_obj_voltage_args_t *

args

)

Create a new Voltage Sensor instance.

Parameters

[in]

args

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

Returns

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

<0 otherwise

lwm2m_object_voltage_update_value()

void lwm2m_object_voltage_update_value	(	const lwm2m_client_data_t *	client_data,
		uint16_t	instance_id,
		int16_t	value
	)

Update the value of the voltage 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.