Forwarding data to the server
We'll need a device to transfer data from the sensors (LoRa radio) to the server; this device is called a gateway, and usually made using a Raspberry Pi and various modules.
1. The Raspberry Pi gateway
1.1. How to make the gateway?
The gateway is composed of at least a Raspberry Pi board, a RFM95 radio module for receiving sensors data and a PCF8523 real-time clock, that will keep track of the date even when the network or the Raspberry are disconnected.
As a main gateway board, you can use either of these Raspberry Pi :
- Raspberry Pi 3A+
- Raspberry Pi 3B+
- Raspberry Pi Zero W
Connect the to modules to the board according to the following diagram:
1.2. How to make it work?
Once your gateway is assembled, you'll need to run a program that will send data to the server; this procedure follows three simple steps:
- asking for a gateway key (or rolling your own server);
- copying the example code;
- adding your encryption key to the gateway and running the code!
If you went to this section, you should already have visited the previous page about the sensors; if not, please read at least section 3 of the previous page; therefore, you're supposed to have downloaded the entire Task03 directory of the main Github repository.
First, please contact François Rebaudo to get a gateway key that will allow you to post data to the PI2P project server.
Once you have the key, you can simply go to the sit_final repository; the file there are required for encryption between the sensor and the gateway; you'll need to compile and install them with the following commands:
Nothing should go wrong, and you can now go to the gateway directory, and edit the file forward.py, to match the following:
- edit the
BASE_URLto match the server you're using (https://pi2p.ird.fr/sensors); - the
GW_KEYis the gateway key that was given to you by the server owner; - the server owner should also give you the ids of the sensors he configured for you, and you should match these ids in the
SENSOR_MAPobject; by default,"T"is temperature from the DS18B20,"H"is humidity from DHT11/22 and"U"is temperature from the DHT11/22.
Everything should be fine, so you can now execute python3 forward.py, and power a remote sensor to test your gateway.