Datasheet

Table Of Contents

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SX1272/73

WIRELESS, SENSING & TIMING DATASHEET

Rev. 2 - July 2014

In continuous mode the received packet processing sequence is given below.

1 Whilst in Sleep or Stand-by mode select RXCONT mode.

2 Upon reception of a valid header CRC the

RxDone interrupt is set. The radio remains in RXCONT mode waiting for the

next RX LoRa

packet.

3 The

PayloadCrcError flag should be checked for packet integrity.

4 If packet has been correctly received the FIFO data buffer can be read (see below).

5 The reception process (steps 2 - 4) can be repeated or receiver operating mode exited as desired.

In continuous mode status information are available only for the last packet received, i.e. the corresponding registers

should be read before the next

RxDone arrives.

Payload Data Extraction from FIFO

In order to retrieve received data from FIFO the user must ensure that ValidHeader, PayloadCrcError, RxDone and

RxTimeout interrupts in the status register RegIrqFlags are not asserted to ensure that packet reception has terminated

successfully (i.e. no flags should be set).

In case of errors the steps below should be skipped and the packet discarded. In order to retrieve valid received data from

the FIFO the user must:

 RegRxNbBytes Indicates the number of bytes that have been received thus far.

 RegFifoAddrPtr is a dynamic pointer that indicates precisely where the Lora modem received data has been written up

to.

 Set RegFifoAddrPtr to RegFifoRxCurrentAddr. This sets the FIFO pointer to the location of the last packet received in

the FIFO. The payload can then be extracted by reading the register RegFifo, RegRxNbBytes times.

Alternatively, it is possible to manually point to the location of the last packet received, from the start of the current

packet, by setting RegFifoAddrPtr to RegFifoRxByteAddr minus RegRxNbBytes. The payload bytes can then be read

from the FIFO by reading the RegFifo address RegRxNbBytes times.

Packet Filtering based on Preamble Start

The LoRa

modem does not automatically filter received packets based upon an address. However, the SX1272/73

permits software filtering of the received packets based on the contents of the first few bytes of payload. A brief example is

given below for a 4 byte address, however, the address length can be selected by the designer.

The objective of the packet filtering process is to determine the presence, or otherwise, of a valid packet designed for the

receiver. If the packet is not for the receiver then the radio returns to sleep mode in order to improve battery life.