原标题：基于ST STM32L051的LoRaWAN抄水表解决方案

　　抄水表的方案有很多种技术可以实现，目前主要有有线抄表和无线抄表两大类别。在各种抄表技术中，无线抄表技术是比较容易被接受的，因为不需要现场布线，安装方便维护更新简单。但一些无线技术方案也存在着一些应用上的问题和不足，如FSK距离短、穿透力差、无线信号不稳定，而GPRS虽然网络好但又太耗电。LoRa技术的出现为抄表应用解决了传输距离、网络信号和耗电等应用上的问题。本文推荐一个基于LoRaWAN的智慧水务解决方案。

　　下图是基于LoRaWAN的水表/气表抄表系统应用框图：

　　本方案采用了LoRaWAN网络的标准架构，并将传统的水表终端改造成了LoRa水表终端，网络服务器部分还针对抄水表的数据业务特点进行了相应地优化。

　　▌LoRa智慧水务解决方案网络架构

　　下图是本方案的网络系统架构示意图：

　　【终端层】 - 方案提供了具有LoRa功能的PCBA，并且对目前的水气表PCBA的刷胶工艺进行了改进，采用防水盒式设计，方便后期的维护和软件更新。LoRa天线针对水表的安装环境进行了设计和优化，收发性能良好。

　　【网络层】- 采用了基于LoRaWAN的协议标准，并针对水表数据业务进行了优化处理。低功耗广域(LPWA)技术为大规模数据采集系统的应用提供了很好的技术支撑。针对LoRa网络信号的盲区，还设计了一款低成本的LoRa中继设备，解决了LoRa网络覆盖的问题。目前，从试点的效果来看比较理想。

　　【云平台】 - 智能硬件云平台提供集群部署、协议和服务管理等。LoRaWAN的网络服务器(NS)可以私有云部署，也可以公有云部署，更方便项目灵活地部署。

　　【应用层】 - 智能水务应用平台负责运维管理、数据可视化等

　　▌LoRaWAN 水表产品

　　下图是水表和模块实物图片：

　　为解决后期的MCU固件升级更新问题，本方案还设计了一款专用工具和软件，可通过近距离无线升级方式(OTA)，无需拆卸表壳，节省了维护成本，提高了效率。

　　主要特性：

　　• 最低-147dBm的高链路灵敏度

　　• 最大20公里的空空通信距离

　　• 1.5~2.5公里的城市密集区域通信距离

　　• 最大20层的跨楼层通信能力

　　• 最低5uA的超低功耗设计，确保产品6~10年的有效使用周期

　　• 高精度脉冲数目计数误差：±1个/年

　　• 低延迟远程唤醒功能

　　• 智能OTA升级功能

　　• 先进的防偷盗水功能，远程自动报警

　　• 支持外部磁信号强制触发唤醒功能

　　• 无缝对接水表设备云及自来水厂管理平台，保证数据安全性

　　▌LoRaWAN 模组

　　LoRaWAN模组的主芯片采用了Semtech公司的SX1278和ST公司的 STM32L051C8。模组频率采用了中国适用频段470-510MHz，支持LoRaWAN标准协议。

　　主要特性：

　　• 内置STM32L051C8处理器

　　• 支持LoRaWAN™ 1.0协议栈

　　• 支持LoRaWAN™ Class A、Class C

　　• 使用TCXO

　　• 最大链路预算可达168dB

　　• 127dB的RSSI动态范围

　　• 9.9mA低接收电流，200nA待机电流

　　• 支持AES128/SM4等多种安全加密

　　• 支持FSK、GFSK、LoRa™等调制方式

　　• 自动射频信号检测,CAD模式和超高速AFC

　　• 多种加密技术(AES128/SM4)保证了网络和数据的安全。

　　▌LoRaWAN 网关

　　LoRaWAN网关符合LoRaWAN协议规范，支持多信道并发，POE供电，带有GPS功能，回程采用3G/4G/WiFi等多种链路。LoRaWAN网关经过抗干扰优化设计，可满足各种不同的环境应用。

　　主要特性：

　　• 可同时接收同一信道流量

　　• 易于扩展，增加网络容量

　　• 可同时解调2MHz的带宽

　　• 简单的星形网络一没有延迟

　　• 自适应链路速率

　　• 同时通讯节点10万指标

　　• 发射功率27dBm

　　• 链路灵敏度-157dBm

　　▌LoRaWAN 网络服务器

　　LoRa网络服务器可进行私有化部署或公有云部署，公有云如阿里云等。

　　主要特性：

　　• LoRaWAN. MAC

　　• GW网管及配置

　　• EN配置及OTA

　　• 与应用服务器数据交互

　　• 基于源数据选择最佳的下游路径

　　• RTCM高精度定位差分数据广播( 选购)

　　• 调度下行流量

　　• GWM接入数量：2000台

　　• EN接入数量：>100万

　　▌云平台及应用平台

　　智能水表应用平台主要功能介绍：

　　• 抄表管理(设置，小区、水厂管理等)

　　• 产品生命周期管理(测试、安装、追溯)

　　• 运营管理(监控、升级、记录等)

　　• 数据可视化(统计、查询、图表、报表)

　　智能硬件云平台主要功能介绍：

　　• 采用Dubbo分布式框架支持大容量高并发请求

　　• 采用Docker容器集群部署节约资源和时间

　　• 支持OAuth2.0协议认证授权

　　• 支持多协议通信(HTTP, MQTT, TCP/UDP等)

　　• 实时请求服务治理和服务监控

　　▌智能抄表管理平台、收费平台&智慧生活App

　　下图是抄表系统后台管理界面截图和App界面截图，提供了可视化的数据管理后台。

　　▌产品测试及测试设备

　　产品的研发和生产离不开测试仪器仪表，专业完善的仪器仪表保证了方案设计的品质。

　　▌解决方案部署现场

　　下图是方案的部署现场情况，一个LoRaWAN网络基本上覆盖了6幢楼，经过现场的设计和优化，基本做到了100% 成功抄表。

　　▌结语

　　本方案基于标准的LoRaWAN协议而设计，针对抄水表的数据业务而优化。在实际进行LoRaWAN网络部署的时，难免会存在信号的盲区，为此专门设计了低成本LoRaWAN网络的补盲中继器，实现了LoRaWAN网络信号的无死角覆盖。为方便水表的维护和升级还设计了一款空中升级工具，无需打开表壳，就可以进行MCU固件的升级操作，方便了现场的维护和软件更新。

　　本方案同样适用于抄气表等其他的应用。

　　场景应用图

　　展示板照片

　　方案方块图

　　核心技术优势

　　 实现了居民用水表的集中抄报

　　 并通过后台管理实现了智能化的数据管理

　　方案规格

　　1. 内置STM32L051C8处理器

　　2. 支持LoRaWAN™ 1.0协议栈

　　3. 支持LoRaWAN™ Class A、Class C

　　4. 使用TCXO

　　5. 最大链路预算可达168dB

　　6. 127dB的RSSI动态范围

　　7. 9.9mA低接收电流，200nA待机电流

　　8. 支持AES128/SM4等多种安全加密

　　9. 支持FSK、GFSK、LoRa™等调制方式

　　10. 自动射频信号检测,CAD模式和超高速AFC

　　【STM32L051C8】

　　Ultra-low-power ARM Cortex-M0+ MCU with 64 Kbytes Flash, 32 MHz CPU

　　The access line ultra-low-power STM32L051x6/8 microcontrollers incorporate the high-performance Arm® Cortex®-M0+ 32-bit RISC core operating at a 32 MHz frequency, a memory protection unit (MPU), high-speed embedded memories (64 Kbytes of Flash program memory, 2 Kbytes of data EEPROM and 8 Kbytes of RAM) plus an extensive range of enhanced I/Os and peripherals.

　　The STM32L051x6/8 devices provide high power efficiency for a wide range of performance. It is achieved with a large choice of internal and external clock sources, an internal voltage adaptation and several low-power modes.

　　The STM32L051x6/8 devices offer several analog features, one 12-bit ADC with hardware oversampling, two ultra-low-power comparators, several timers, one low-power timer (LPTIM), three general-purpose 16-bit timers and one basic timer, one RTC and one SysTick which can be used as timebases. They also feature two watchdogs, one watchdog with independent clock and window capability and one window watchdog based on bus clock.

　　Moreover, the STM32L051x6/8 devices embed standard and advanced communication interfaces: up to two I2C, two SPIs, one I2S, two USARTs, a low-power UART (LPUART), .

　　The STM32L051x6/8 also include a real-time clock and a set of backup registers that remain powered in Standby mode.

　　The ultra-low-power STM32L051x6/8 devices operate from a 1.8 to 3.6 V power supply (down to 1.65 V at power down) with BOR and from a 1.65 to 3.6 V power supply without BOR option. They are available in the -40 to +125 °C temperature range. A comprehensive set of power-saving modes allows the design of low-power applications.

　　Key Features

　　Ultra-low-power platform

　　1.65 V to 3.6 V power supply

　　-40 to 125 °C temperature range

　　0.27 μA Standby mode (2 wakeup pins)

　　0.4 μA Stop mode (16 wakeup lines)

　　0.8 μA Stop mode + RTC + 8 KB RAM retention

　　88 μA/MHz in Run mode

　　3.5 μs wakeup time (from RAM)

　　5 μs wakeup time (from Flash memory)

　　Core: Arm® 32-bit Cortex®-M0+ with MPU

　　From 32 kHz up to 32 MHz max.

　　0.95 DMIPS/MHz

　　Memories

　　Up to 64 KB Flash memory with ECC

　　8KB RAM

　　2 KB of data EEPROM with ECC

　　20-byte backup register

　　Sector protection against R/W operation

　　Up to 51 fast I/Os (45 I/Os 5V tolerant)

　　Reset and supply management

　　Ultra-safe, low-power BOR (brownout reset) with 5 selectable thresholds

　　Ultra-low-power POR/PDR

　　Programmable voltage detector (PVD)

　　Clock sources

　　1 to 25 MHz crystal oscillator

　　32 kHz oscillator for RTC with calibration

　　High speed internal 16 MHz factory-trimmed RC (+/- 1%)

　　Internal low-power 37 kHz RC

　　Internal multispeed low-power 65 kHz to 4.2 MHz RC

　　PLL for CPU clock

　　Pre-programmed bootloader

　　USART, SPI supported

　　Development support

　　Serial wire debug supported

　　Rich Analog peripherals

　　12-bit ADC 1.14 Msps up to 16 channels (down to 1.65 V)

　　2x ultra-low-power comparators (window mode and wake up capability, down to 1.65 V)

　　7-channel DMA controller, supporting ADC, SPI, I2C, USART, Timers

　　7x peripheral communication interfaces

　　2x USART (ISO 7816, IrDA), 1x UART (low power)

　　Up to 4x SPI 16 Mbits/s

　　2x I2C (SMBus/PMBus)

　　9x timers: 1x 16-bit with up to 4 channels, 2x 16-bit with up to 2 channels, 1x 16-bit ultra-low-power timer, 1x SysTick, 1x RTC, 1x 16-bit basic, and 2x watchdogs (independent/window)

　　CRC calculation unit, 96-bit unique ID

　　All packages are ECOPACK®2

　　The access line ultra-low-power STM32L051x6/8 microcontrollers incorporate the high-performance Arm® Cortex®-M0+ 32-bit RISC core operating at a 32 MHz frequency, a memory protection unit (MPU), high-speed embedded memories (64 Kbytes of Flash program memory, 2 Kbytes of data EEPROM and 8 Kbytes of RAM) plus an extensive range of enhanced I/Os and peripherals.

　　The STM32L051x6/8 devices provide high power efficiency for a wide range of performance. It is achieved with a large choice of internal and external clock sources, an internal voltage adaptation and several low-power modes.

　　The STM32L051x6/8 devices offer several analog features, one 12-bit ADC with hardware oversampling, two ultra-low-power comparators, several timers, one low-power timer (LPTIM), three general-purpose 16-bit timers and one basic timer, one RTC and one SysTick which can be used as timebases. They also feature two watchdogs, one watchdog with independent clock and window capability and one window watchdog based on bus clock.

　　Moreover, the STM32L051x6/8 devices embed standard and advanced communication interfaces: up to two I2C, two SPIs, one I2S, two USARTs, a low-power UART (LPUART), .

　　The STM32L051x6/8 also include a real-time clock and a set of backup registers that remain powered in Standby mode.

　　The ultra-low-power STM32L051x6/8 devices operate from a 1.8 to 3.6 V power supply (down to 1.65 V at power down) with BOR and from a 1.65 to 3.6 V power supply without BOR option. They are available in the -40 to +125 °C temperature range. A comprehensive set of power-saving modes allows the design of low-power applications.

　　Key Features

　　Ultra-low-power platform

　　1.65 V to 3.6 V power supply

　　-40 to 125 °C temperature range

　　0.27 μA Standby mode (2 wakeup pins)

　　0.4 μA Stop mode (16 wakeup lines)

　　0.8 μA Stop mode + RTC + 8 KB RAM retention

　　88 μA/MHz in Run mode

　　3.5 μs wakeup time (from RAM)

　　5 μs wakeup time (from Flash memory)

　　Core: Arm® 32-bit Cortex®-M0+ with MPU

　　From 32 kHz up to 32 MHz max.

　　0.95 DMIPS/MHz

　　Memories

　　Up to 64 KB Flash memory with ECC

　　8KB RAM

　　2 KB of data EEPROM with ECC

　　20-byte backup register

　　Sector protection against R/W operation

　　Up to 51 fast I/Os (45 I/Os 5V tolerant)

　　Reset and supply management

　　Ultra-safe, low-power BOR (brownout reset) with 5 selectable thresholds

　　Ultra-low-power POR/PDR

　　Programmable voltage detector (PVD)

　　Clock sources

　　1 to 25 MHz crystal oscillator

　　32 kHz oscillator for RTC with calibration

　　High speed internal 16 MHz factory-trimmed RC (+/- 1%)

　　Internal low-power 37 kHz RC

　　Internal multispeed low-power 65 kHz to 4.2 MHz RC

　　PLL for CPU clock

　　Pre-programmed bootloader

　　USART, SPI supported

　　Development support

　　Serial wire debug supported

　　Rich Analog peripherals

　　12-bit ADC 1.14 Msps up to 16 channels (down to 1.65 V)

　　2x ultra-low-power comparators (window mode and wake up capability, down to 1.65 V)

　　7-channel DMA controller, supporting ADC, SPI, I2C, USART, Timers

　　7x peripheral communication interfaces

　　2x USART (ISO 7816, IrDA), 1x UART (low power)

　　Up to 4x SPI 16 Mbits/s

　　2x I2C (SMBus/PMBus)

　　9x timers: 1x 16-bit with up to 4 channels, 2x 16-bit with up to 2 channels, 1x 16-bit ultra-low-power timer, 1x SysTick, 1x RTC, 1x 16-bit basic, and 2x watchdogs (independent/window)

　　CRC calculation unit, 96-bit unique ID

　　All packages are ECOPACK®2

　　CIRCUIT DIAGRAM CIRCUIT DIAGRAM

　　【SX1278】

　　137MHz to 525MHz Long Range Low Power Transceiver

　　The SX1276/77/78/79 transceivers feature the LoRa® long range modem that provides ultra-long range spread spectrum communication and high interference immunity whilst minimizing current consumption.

　　Using Semtech’s patented LoRa modulation technique SX1276/77/78/79 can achieve a sensitivity of over -148dBm using a low cost crystal and bill of materials. The high sensitivity combined with the integrated +20dBm power amplifier yields industry leading link budget making it optimal for any application requiring range or robustness. LoRa also provides significant advantages in both blocking and selectivity over conventional modulation techniques, solving the traditional design compromise between range, interference immunity and energy consumption.

　　Overview

　　Features

　　LoRaTM Modem 168dB maximum link budget

　　+20dBm - 100mW constant RF output vs. V supply

　　+14dBm high efficiency PA

　　Programmable bit rate up to 300kbps

　　High sensitivity: down to -148dBm

　　Bullet-proof front end: IIP3 = -11dBm

　　Excellent blocking immunity

　　Low RX current of 9.9mA, 200nA register retention

　　Fully integrated synthesizer with a resolution of 61Hz

　　FSK, GFSK, MSK, GMSK, LoRa and OOK modulation

　　Built-in bit synchronizer for clock recovery

　　Preamble detection

　　127dB Dynamic Range RSSI

　　Automatic RF Sense and CAD with ultra-fast AFC

　　Packet engine up to 256 bytes with CRC

　　Built-in temperature sensor and low battery indicator

　　Applications

　　Automated Meter Reading

　　Home and Building Automation

　　Wireless Alarm and Security Systems

　　Industrial Monitoring and Control

　　Long range Irrigation Systems

　　Packaging

　　QFN 28

　　Order Codes

　　SX1278IMLTRT - Pb-free, Halogen free, RoHS/WEEE compliant product