LwM2M: working with devices
The LwM2M page lists every device that registered. Its device page shows the registration, all objects the device announced with their resources and last known values, and the device's traffic.
Operations
| Button | What happens |
|---|---|
| Read | Reads a resource, an instance or a whole object |
| Write | Writes a new value to a writable resource, e.g. switches a light on or off |
| Execute | Starts an action on the device, e.g. Reset Error Code |
| Observe | The device reports the value on its own whenever it changes (notifications), until you cancel |
| Discover | Asks the device which resources and attributes an object or instance has |
Reboot, factory reset, the bootstrap trigger, changes to the Security object and firmware updates are limited to administrators. Data the device sends on its own (LwM2M Send, e.g. a heartbeat) and notifications update the values on the device page and appear in its activity list.
Devices that sleep (queue mode)
A device in queue mode (binding UQ, or queue mode in LwM2M 1.1) is not always reachable. Requests to
it are queued and sent as soon as the device is awake again: after it sent a Registration Update, a Send or a
notification. The device page shows queued requests until they are answered.
Content formats
Choose the format on the device page; the list there only shows the formats your device announced in its Register message.
| Format | Content-Format | LwM2M version | Note |
|---|---|---|---|
| TLV | 11542 | 1.0, 1.1 | The format every LwM2M 1.0 client supports |
| SenML JSON | 110 | 1.1 | Readable, larger messages |
| SenML CBOR | 112 | 1.1 | Compact, the usual default of 1.1 clients |
| LwM2M JSON | 11543 | 1.0 | Older JSON format of LwM2M 1.0 |
| Plain text | 0 | 1.0, 1.1 | Single resources only |
| Opaque | 42 | 1.0, 1.1 | Single opaque resources only |
| CBOR | 60 | 1.1 | Single resources only |
Objects
The server knows all objects of the OMA LwM2M registry, with their older versions. A device gets the object
version it announces in its Register message (</3>;ver=1.1), otherwise the first version of the
object. See the list of objects.