Solution on Lora Transmission System

1.?System Overview

The system adopts the LORA (Long Range) technology in the Low Power Wide-Area Network (Low Power Wide-Area Network) to realize the parameter configuration, data collection, alarm processing and other applications of the remote terminal equipment in the industrial field. The system consists of application server, LORA base station and LORA terminal. The application server is oriented to users to realize various applications of remote terminal equipment; the LORA base station can realize data interaction with the application server through Ethernet, WIFI, EIA-485, 4G, etc., and communicate wirelessly with the remote LORA terminal through the LORA network (private protocol); LORA terminals include thermometers, pH meters, pressure gauges, flow meters, etc. All terminals are powered by batteries and communicate with the LORA base station through the LORA network.

2.?LORA Base Station Solution

2.1?????Base Station Hardware Composition

The base station hardware consists of a power management unit (see Fig.2 power structure diagram for details), MCU processing unit, LORA communication unit, EIA-485 unit, 4G unit, Ethernet unit, WIFI unit, Bluetooth unit (reserved) and surge and static protection circuit, etc., see Fig3 base station system diagram for details.

2.1.1 Power Supply Topology

2.1.2 Power supply topology

2.2 Introduction to core hardware selection

2.2.1 Power management unit

The external input power of the base station is AC 220V, and the AC-DC module needs to be used to convert the AC power to realize the voltage conversion from AC 220V to DC 12V. The characteristics of this module are as follows:

◎ Input voltage: 85-264VAC/100-370VDC

◎ Output power: 12V/1.66A @20W

◎ Conversion efficiency: 82% @230VAC?

◎ Isolation voltage: 4000VAC

◎ Working temperature: -40℃ ~ +85℃

◎ EMC performance: CISPR32/EN55032 CLASSS B

◎ Mechanical size: 53.8mm(L)*28.8mm(W)*23.5mm(H）

2.2.2 MCU processing unit

The MCU processor adopts Cortex M4 microprocessor and its characteristics are as follows:

◎ ARM 32-bit Cortex-M4+FPU

◎ 100-PIN LQFP Package

◎ 168MHz highest main frequency

◎ 1Mbyte FLASH, 192+4Kbytes SRAM

◎ 4*USARTs/2*UARTs, 3*SPIs, 2*CAN, SDIO, MII/RMII

◎ 3*12bits, 2.4MSPS A/D, 24 channels

2.2.3 LORA communication unit

The LORA communication unit is connected to the main board of the base station through the Mini-PCIe interface. The communication unit uses the E22-400M30S LORA core communication module provided by Chengdu Ebyte Electronic Technology Co., Ltd. This module uses Semtech's latest SX1268 chip, which is higher than the previous generation SX1278 Compared with SX1268, it has higher transmitted power, lower receive current, and supports more communication bit rates. This module has a built-in power amplifier, and the maximum transmission power can reach 30dBm. The module features are as follows:

◎ Working frequency band: 410~493MHz

◎ LORA mode supports 0.018~62.5Kpbs bit rate

◎ Maximum transmit power 1W, multi-level adjustable by software

◎ Built-in PA+LNA, the communication distance can reach 12km under ideal

conditions

◎ Support 2.5~5.5V power supply, the maximum working current is 610mA

◎ Working temperature: -40℃ ~ +85℃

● Note: The LORA communication unit is designed separately from the main board, and the two are connected through 52-PIN MINI-PCIe. The LORA communication unit includes a LORA communication module, a control MCU, and an antenna interface (IPEX format). At the same time, the SPI control pins and IO pins of the module lead to the MINI-PCIe interface.

2.2.4 EIA-485 Communication Unit

The RS485 communication unit adopts the small-volume automatic transceiver control isolated 485 transceiver with its characteristics showing below:

◎ Maximum support 500Kbps baud rate

◎ 3-5V wide operating voltage

◎ Up to 64 nodes are supported

◎ Isolation voltage 2500V

◎ Working temperature: -40℃ ~ +105℃

2.2.5 4G communication unit

The communication module has the characteristics:

◎ Supply voltage: 3.3V-4.3V, typically 3.8V

◎ Working temperature: -40℃ ~ +85℃

◎ 3GPP E-UTRA Release 11

◎ The maximum downlink rate is 150Mbps, and the maximum uplink rate is 50Mbps

2.2.6 WIFI unit

WIFI unit is a low-power 802.11 b/g/n module designed for the application of wireless network communication in embedded systems. The module features are as follows:

◎ Supply voltage: 3.0V-3.6V, typically 3.3V

◎ Working temperature: -40℃ ~ +85℃

◎ Wireless standard: 802.11 b/g/n

◎ Support Socket transparent transmission

◎ Serial rate up to 3Mbps

2.2.7 Bluetooth unit

?The Bluetooth unit adopts the Bluetooth SOC chip with the peripheral circuit to realize the BLE5.0 function. The characteristics of the Bluetooth SOC are as follows:

◎ 64 MHz Cortex-M4 with FPU

◎ 512/256KB Flash, 64/32KB RAM

◎ Bluetooth Low Energy and Bluetooth mesh

Note: Bluetooth is only reserved for hardware, and Bluetooth software functions are not within the scope of development.

2.3 Introduction to the embedded software functions of the base station

The LORA base station is located in the middle layer of the entire transmission system and is used to connect the upper application server and the bottom terminal. At the same time, the base station has a storage function and can be used independently in an offline state (unable to connect to the application server) to receive data from the bottom terminal and store it.

List of software features:

◎ Support any one of Ethernet, 4G, WIFI, RS485 to connect to the upper server;

◎ The upper server connection parameters are saved after power off;

◎ LORA supports 2 data channels, 1 alarm channel, and 1 configuration channel;

◎ The LORA configuration channel supports the air wake-up function;

◎ LORA alarm channel and configuration channel support ACK confirmation;

◎ The LORA terminal access adopts the code matching method, and non-coded terminals are not allowed to access;

◎ LORA data ASE128+ software coded double encryption;

◎ LORA communication parameters can be flexibly configured through the upper server;

◎ LORA terminal information is saved locally.

2.4?????LORA base station technical indicators

3?LORA Terminal Solution

3.1?????Terminal hardware composition

Base station hardware consists of external battery, power management unit, MCU processing unit and peripherals, LORA

Composition of communication unit and external probe, see Fig5 terminal system diagram for details.

3.2 Introduction to core hardware selection

3.2.1 External battery

?????The LORA terminal is powered by an external battery. The proposed battery uses a battery pack composed of a lithium-sub-battery + a composite capacitor, considering the capacity of the battery pack and the discharge current. The specifications are as follows:

◎ Nominal capacity: 19000mAh

◎ Nominal Voltage: 3.6V

◎ Maximum contact discharge current: 500mA

◎ Working temperature: -60℃ ~ +85℃

3.2.2 MCU processing unit

The MCU processor with the characteristics of the processor showing below:

◎ ARM 32-bit Cortex-M3

◎ 48-PIN LQFP Package

◎ 32MHz highest main frequency

◎ 64Kbytes FLASH, 10Kbytes SRAM

◎ 3*UARTs, 2*SPIs

◎ 1.45uA Stop mode + RTC

3.2.3 LORA communication unit

The LORA communication unit uses Semtech's latest SX1268 chip. Compared with the previous generation SX1278, the SX1268 has higher transmission power and lower Receive current while supporting more communication bit rates. The module features are as follows:

◎ Working frequency band: 410~493MHz

◎ LORA mode supports 0.018~62.5Kpbs bit rate

◎ Maximum transmit power 1W, multi-level adjustable by software

◎ Built-in PA+LNA, the communication distance can reach 7km under ideal conditions

◎ Ultra-small size, 14*20mm

◎ Working temperature: -40℃ ~ +85℃

4. LORA terminal embedded software function introduction

The LORA terminal software realizes the data upload of the terminal probe, and at the same time realizes functions such as alarm information upload and real-time processing of configuration information (wake-up in the air).

List of software features:

◎ Support wake-up over the air;

◎ Support measurement data calibration;

◎ Data, alarm, configuration channel transmission;

◎ STOP+RTC+ACTIVE extremely low power mode.

5. LORA terminal technical indicators

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