RFM92 Datasheet, PDF (69/126 Pages) List of Unclassifed Manufacturers – Low Power Long Range Transceiver Module

RFM92W/93W V3.0
Optional DC free data coding
CRC checksum calculation
Preamble
Sync Word Address
0 to 65536 bytes 0 to 8 bytes byte
Message
Up to 2047 bytes
CRC
2-bytes
Payload
(min 1 byte)
Fields added by the packet handler in Tx and processed and removed in Rx
Optional User provided fields which are part of the payload
Message part of the payload
Figure 33. Fixed Length Packet Format
Variable Length Packet Format
Variable length packet format is selected when bit PacketFormat is set to 1.
This mode is useful in applications where the length of the packet is not known in advance and can vary over time. It is then
necessary for the transmitter to send the length information together with each packet in order for the receiver to operate
properly.
In this mode the length of the payload, indicated by the length byte, is given by the first byte of the FIFO and is limited to
255 bytes. Note that the length byte itself is not included in its calculation. In this mode the payload must contain at least 2
bytes i.e. length + address or message byte.
An illustration of a variable length packet is shown below. It contains the following fields:
Š Preamble (1010...)
Š Sync word (Network ID)
Š Length byte
Š Optional Address byte (Node ID)
Š Message data
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