Hardware

Specifications

The SX1272 chipset has been developed by the company Semtech. Based on this chipset, Libelium created the Waspmote-compliant LoRa module (or SX1272 module).

Module

Dual frequency band

Transmission power

Sensitivity

Channels

Distance

SX1272

863-870 MHz (Europe)

14 dBm

-134 dBm

8

22+ km

(13.4+ miles)

SX1272

902-928 MHz (US)

14 dBm

-134 dBm

13

22+ km

(13.4+ miles)

Figure: LoRa module
Figure: LoRa module with 4.5 dBi antenna

The user must keep in mind that there are two different antennas for LoRa modules regarding the frequency band: 868 or 900 MHz. Although the appearance of these antennas is the same, the user must choose which one needs to be purchased.

Note: It is not recommended to work without an antenna screwed to the module. The module could be damaged due to RF reflections.

The frequency used in Europe is the free ISM band of 868 MHz, using 8 channels with a bandwidth of 0.3 MHz per channel. That is shown in the following figure.

Figure: Frequency channels in the 868 MHz band

Note: These channels were chosen arbitrarily, according to the UN-111 appeared in the Spanish BOE-A-2013-4845. If necessary, users can select the appropriate channels according to their country regulations.

The frequency used in USA, Canada, Australia, Singapore or Israel is the free ISM band of 900 MHz, using 13 channels with a bandwidth of 2.16 MHz per channel. It is shown in the following figure.

Figure: Frequency channels in the 900 MHz band

Note: These channels were chosen arbitrarily; they fit the channels used by the equivalent XBee 900 MHz. If necessary, users can select the appropriate channels according to their country regulations.

Channel Number

Central frequency

Channel Number

Central frequency

CH_10_868

865.20 MHz

CH_00_900

903.08 MHz

CH_11_868

865.50 MHz

CH_01_900

905.24 MHz

CH_12_868

865.80 MHz

CH_02_900

907.40 MHz

CH_13_868

866.10 MHz

CH_03_900

909.56 MHz

CH_14_868

866.40 MHz

CH_04_900

911.72 MHz

CH_15_868

866.70 MHz

CH_05_900

913.88 MHz

CH_16_868

867 MHz

CH_06_900

916.04 MHz

CH_17_868

868 MHz

CH_07_900

918.20 MHz

CH_08_900

920.36 MHz

CH_09_900

922.52 MHz

CH_10_900

924.68 MHz

CH_11_900

926.84 MHz

CH_12_900

915 MHz

Figure: Channels used by the LoRa modules in 868 MHz and 900 MHz

Note: Due to the propagation characteristics of the 868/900 MHz bands, the near field effect could make that 2 modules cannot communicate if they are placed very close (\< 1 m). We suggest to keep a minimum distance of 3 or 4 meters between modules.

Power level

Regarding the energy section, the transmission power can be adjusted to several values:

Parameter

SX1272 power level

'L'

0 dBm

'H'

7 dBm

'M'

14 dBm

Figure: SX1272 output power level

How to connect the module

This module must be connected to the SOCKET0 placed in the Waspmote board.

Figure: Module connected to Waspmote in SOCKET0

Note: In case of using Waspmote v12, the LoRa module can only be used in special Waspmote v12 units which have been modified to drive the SPI pins to SOCKET0.

Topology

The LoRa module does not implement any security method. Encryption is provided through the Waspmote Encryption library. Specifically, through the AES algorithm with symmetric key, with a length of 128, 192 or 256 bits.

The classic layout of this type of network is Star topology (shown in the figure), as the nodes establish point to point connections with brother nodes through the use of parameters such as the Node Address.

Figure: Star topology

Note: OTA programming is not implemented for the LoRa module. Due to its low datarate, it would take much time to send one program.