The SX1272 chipset has been developed by the company Semtech. Based on this chipset, Libelium created the Waspmote-compliant LoRa module (or SX1272 module).
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.
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.
Regarding the energy section, the transmission power can be adjusted to several values:
Figure: SX1272 output power level
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.
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.