RFM95 datasheet(23/121 Pages) HOPERF

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Page 23

RFM95/96/97/98(W)

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WIRELESS & SENSING

PRELIMINARY

DATASHEET

4.1.1. Link Design Using the

LoRaTM Modem

4.1.1.1. Overview

The LoRaTM modem is setup as shown in the following figure. This configuration permits the simple replacement of the FSK

modem with the LoRaTM modem via the configuration register setting RegOpMode. This change can be performed on the

fly (in Sleep operating mode) thus permitting the use of both standard FSK or OOK in conjunction with the long range

capability. The LoRaTM modulation and demodulation process is proprietary, it uses a form of spread spectrum modulation

combined with cyclic error correction coding. The combined influence of these two factors is an increase in link budget and

enhanced immunity to interference.

Figure 4.

LoRaTM Modem Connectivity

A simplified outline of the transmit and receive processes is also shown above. Here we see that the LoRaTM modem has an

independent dual port data buffer FIFO that is accessed through an SPI interface common to all modes. Upon selection of

LoRaTM mode, the configuration register mapping of the RFM95/96/97/98(W) changes. For full details of this change

please consult the register description of Section 6.

So that it is possible to optimise the LoRaTM modulation for a given application, access is given to the designer to three

critical design parameters. Each one permitting a trade off between link budget, immunity to interference, spectral

occupancy and nominal data rate. These parameters are spreading factor, modulation bandwidth and error coding rate.

RFM95 Datasheet(PDF) 23 Page - Shenzhen Hope Microelectronics Co., Ltd.