USER MANUAL
STM 550B / EMSIB - EASYFIT MULTISENSOR FOR IOT APPLICATIONS (2.4 GHZ BLE)
© 2020 EnOcean | www.enocean.com
F-710-017, V1.0
STM 550B / EMSIB User Manual | v1.3 | June 2020 | Page 41 / 115
5.5
Payload structure
The payload of STM 550B data telegrams can in general be up to 31 bytes long (depending
on the size of the sensor data) and consists of the following fields:
◼
Length (1 byte)
The Length field specifies the combined length of the following fields and depends on
the size of the Sensor Status field. The minimum length is 13 byte and the maxi-
mum length is 31 byte
◼
Type (1 byte)
The Type field identifies the data type used for this telegram. For STM 550B data
telegrams, this field is always set to
0xFF
to designate manufacturer-specific data
field
◼
Manufacturer ID (2 byte)
The Manufacturer ID field is used to identify the manufacturer of BLE devices based
on assigned numbers. EnOcean has been assigned
0x03DA
as manufacturer ID code.
◼
Sequence Counter (4 byte)
The Sequence Counter is a continuously incrementing counter used for security pro-
cessing. It is initialized to
0
at the time of production and incremented for each tele-
gram (data telegram or commissioning telegram) sent.
◼
Sensor Data (variable size)
The Sensor Data field reports the measured values of the sensors. The encoding of
this field is described in chapter 5.5.1.
◼
Security Signature (4 byte)
The Security Signature is used to authenticate EnOcean BLE sensor data telegrams,
see chapter 6.
Figure 27 below illustrates the general telegram payload structure.
Figure 27
–
Telegram payload structure