What is the difference between EnOcean Frame, Telegram and Subtelegram
This page defines EnOcean Frame, Telegram and Subtelegram and mentions difference between EnOcean Frame, Telegram and Subtelegram.
Introduction: EnOcean technology is wireless self powered energy harvesting technology. The standard specifications are defined in ISO/IEC 14543-3-1X. EnOcean stack includes physical layer, data link layer and network layer specifications. It uses different frequency bands across the world for its operation viz. 868 MHz, 315 MHz, 902 MHz, 928 MHz and 2.4 GHz (for IoT).
EnOcean communication protocol is packet based. It uses three data units viz. frame, subtelegram and telegram. There are two parts in any of the EnOcean device viz. transmitter and receiver. Both transmitter and receiver consists of protocol layers viz. physical layer, data link layer, network layer and upper layers.
The encoded data at the output of physical layer is referred as frame. It is transmitted in serial sequence bit by bit. It contains control (i.e. PRE, SOF, INV and EOF) and synchronization information for receiver. The encoding process at transmitter converts subtelegram into a frame.
Decoding process at the receiver gives subtelegram as output. During decoding process control and synchronization information fields are removed from frame. The figure-1 depicts EnOcean protocol stack showing protocol layers with data units at transmitter and receiver.
One complete telegram consists of maximum of three subtelegrams. Bidirectional communication requires telegrams to have addresses. The addressing of telegram is done by encapsulation mechanism. Telegram type field (i.e. RORG) with 0xA6 value indicates encapsulated telegrams.
As shown in the figure, the subtelegrams are managed by data link layer. The EnOcean Radio Protocol (ERP) is designed to work as unidirectional protocol mostly without any handshaking. To order to maintain reliability during transmission, 3 identical subtelegrams are transmitted within particular time interval.
Subtelegram structure as specified in EnOcean Radio Protocol-1, V1.2
The fields of EnOcean subtelegram are described below.
RORG-CHOICE : Type of subtelegram
DATA : Payload of subtelegram
TXID/SourceID : Unique 4-byte transmitter identity
STATUS : Status of subtelegram transmission from repeater and integrity control mechanism type can be known by this field. This field is absent in switch telegram.
HASH/Checksum : Data integrity check value of all the bytes in a subtelegram.
The total length of ERP1 telegram is 21 bytes (maximum). The subtelegram length is not transmitted in the structure. It is determined by counting total bytes between RORG and HASH.
EnOcean wireless technology Related Links
• EnOcean Radio Protocol-1 V1.2, November 9, 2020
• Visit www.enocean.com for everything you would like to know about EnOcean technology from inventor and pioneer of this energy harvesting wireless technology.
• EnOcean Alliance