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.