How to collect long-distance temperature and humidity on LoRa wireless network

How to collect long-distance temperature and humidity through LoRa wireless network? Equipped with an IoT system to collect temperature and humidity to the cloud server, which can be viewed through a smartphone or other mobile device. With the RNDU470T and the temperature and humidity sensor SHT71, the use of the operating system is eliminated, making the solution simpler.

First, the meaning of the collection system

Temperature and humidity are the two physical parameters that deal with human beings in nature. Whether in production or experimental places, the collection and control of temperature and humidity are very frequent and important, such as computer room, substation, granary, cold storage, books. Museums, museums, pharmaceutical factories, etc. need to monitor the temperature and humidity of the environment. Moreover, networked remote collection of temperature and humidity and alarm is an inevitable trend in the development of modern science and technology.

If you purchase Remy's LoRa terminal and LoRa gateway, you can quickly set up an IoT system that collects temperature and humidity. The system can collect the temperature and humidity on the cloud server and view it through the smartphone as shown in the figure below.

How to collect long-distance temperature and humidity on LoRa wireless network

As shown in the red dotted line above, the RNDU470T and the temperature and humidity sensor SHT71 are used for the rapid design of the Demo system hardware. The development language is ASNI C and the development environment is IAR for STM8. The operating system is not used to reduce the complexity.

Second, the hardware connection

The acquisition system hardware is based on the RNDU470T design and its pins are defined as follows:

Pin No. Pin Name Pin Type Description

1VCCSupply3.3V power supply

2GNDSupply power ground

3RXDD IN/OUTUART Receive

4TXDD IN/OUTUART transmission

5CON1DIN/OUTUART output signal port

6CON2DIN/OUTUART input signal port

7CON3D IN/OUT reserved

8RSTD IN/OUT reset pin

A// fixed pin 1

B / / fixed pin 2

SMA / / welding antenna use

The SHT71 is a temperature and humidity sensor from SENSIRION. Its 4-pin pin is defined as follows:

Pin1234

FuncTIonSCKVDDGNDDATA

The connection between the acquisition system hardware and the SHT71 is shown in the figure on the left. The connection between the acquisition system hardware and the RNDU470T is shown in the right figure below.

How to collect long-distance temperature and humidity on LoRa wireless network

Third, the acquisition system logic

How to collect long-distance temperature and humidity on LoRa wireless network

The main program logic of the acquisition system is as shown in the figure above. It is very simple, based on the simplest software structure: while(1) infinite loop.

After the actual measurement: the acquisition system system collects the 12-bit humidity of the SHT71 for about 62 milliseconds, and the 14-bit temperature is about 216 milliseconds.

When is the temperature and humidity data collected by the acquisition system system suitable for transmission to the RNDU470T? This depends on the RNDU470T timing reporting frequency. If the timing report is 5 seconds, the acquisition system will transmit the temperature and humidity data every 5 seconds (ie, synchronous transmission). Of course, the user can increase the acquisition density (such as once every 1 second), perform a custom calculation (such as calculating the average of 5 acquisitions), and then transmit the data to the RNDU470T.

The timing diagram of the transmission system data transmission and the RNDU470T reporting temperature and humidity data is as follows:

How to collect long-distance temperature and humidity on LoRa wireless network

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