"IoT devices with Bluetooth features provide immediate available data access via smartphones and other gateway devices. But the low-power IoT solution for battery powers is still facing wireless testing and high-energy communication sub-system optimization. Designers must simplify design tasks for designers who are extremely urgent for the listing time schedule.
To help developers should combine their respective SENSORTILE development kits and Bluetooth software professional techniques, which are complicated with low-power design complexity and launch time stress. They launched a simple way to quickly develop battery-powered IoT equipment that meets tight power budget.
IoT hardware and software do not still matter
For designers who wish to use ubiquitous Bluetooth mobile devices, the emergence of integrated Bluetooth solutions makes them like a tiger. In addition to reducing design complexity, ready-made Bluetooth solutions can directly accelerate market delivery, because these solutions have been certified and regulatory requirements. However, for most developers, these tasks that contain multiple sensors with a master MCU combined with a host MCU are still a long and complicated process. In addition, even the most experienced development team, facing the relevant software drivers, the development of middleware and application software may be difficult.
The SENSORTILE development kit of STMic Semiconductors provides a complete set of IOT development solutions, which combines a wireless sensor system board, a pair of carriers and a comprehensive software development kit. The IoT.Over.beacon software platform of ENMO Technologies is designed to use the Sensortile environment to provide unique solutions to minimize the power consumption of IoT designs with Bluetooth features. With the Sensortile kit and the ENMO platform, developers can implement a complete low-power IOT device solution with minimal work, or use the same hardware and software components as the basis for custom design.
Wireless sensor node
As the core component of the kit, the Sensortile core system board is an independent sensor system with a 13.5 mm x 13.5 mm package and has a Bluetooth function. The core system is based on the STM32L4 MCU based on 32-bit ARM® Cortex®-M4F, including the SSD BluenRG Bluetooth transceiver and multiple sensors, all components communicate through the SPI connection or dedicated interface (Figure 1).
ST packs its own full-sized sensor, including LSM6DSM inertial measuring devices (IMU), LSM303AGR electronic compass modules, LPS22HB pressure sensors, and MP34DT04 MEMS microphones. Contained low voltage difference (LDO) regulators, the core plate contains a small balance of BALF-NRG-01D3, which integrates a harmonic filter and a matching network designed for the BluenRG transceiver. TDK ANT016008LCS2442MA1 multi-layer antenna makes the design of the wireless sensor system.
Developers can use two different scenarios to connect core boards to the kit supporting board, or its own system design. On both sides of the board, developers can use a set of pads to the saddle plate or other PC board. The back of the board contains a connector for mounting it to the expansion plate or any other cable or plate having the corresponding connector (Figure 2).
Both the PC plate pad and the back connector take a plurality of MCU pins, including SPI, I2C, and UART interfaces, a pulse density modulation (PDM) interface, multiple digital converters (ADCs), and ST serial line debugging. (SWD) Interface (Figure 3).
Although the core board can be used as a stand-alone solution, the load on the suite provides designers with an alternative to Sensortile development and deployment IoT design. The saddle plate and supporting schematic illustrate how developers use more sensors and other peripherals to expand the core system. The plate includes an integral semiconductor HTS221 sensor for humidity and temperature. In addition, the saddle plate also includes an SD card socket, a Micro-USB interface, a switch, and a battery pack. Designers only need to receive core plates to the respective pads on the saddle, and use more external settings. After the development is completed, the designer can remove the broken SWD interface of the saddle plate when delivering.
The expansion panel of the kit provides a simpler way to develop custom designs. Developers can insert the core plate into the expansion board with a dedicated connector (Figure 2). Similar to SWD interfaces for software development, the expansion board provides more connectors including Micro-USB connectors, audio jacks, and Arduino compatible connector.
Instant deployment
Simply insert the core plate into the expansion board (or weld it to the saddle plate), connect it to the host PC via USB to get the power supply, then download the supported Android or iOS mobile application, you can start exploration IoT design with Bluetooth features. The core system of the development kit has been programmed by firmware that supports three sample applications. These applications use low power Blueth (BLE) with ST Bluems applications suitable for Android or iOS, demonstrate the sensor. Data records to applications such as SD card, MEMS microphone audio flow and sensor data stream.
In addition to providing software for instant deployment SENSORTILE applications, these sample applications can also be used as guidance using the multilayer architecture of Sensortile. Contained ARM Cortex Microcontroller Software Interface Standard (CMSIS) components, the semiconductors provide hardware abstraction layers (HAL) and board-level support packages (BSP) based on their own STM32Cube environment. These layers are in turn with the base hardware interface on the STLCS01V1 core board, STLCX01V1 expansion plate, and STLCR01V1 saddle plate (Figure 4).
The hierarchical architecture although it seems complicated, a simple abstract view of the sensor data acquisition and wireless communication is provided for developers. For example, the BLE stream application demonstrates that developers can call several initialization routines before the primary wait loop (list 1). The main loop waits for critical events, including timers that are used to specify the wait time between sensor data sampling. When the timer handler sets Sendenv = 1, the routine will use a single call.
The SendenvironmentalData routine traverses individual sensors in a stepper method, using the BSP routine to collect data of each sensor. For example, pressure sensor BSP routines BSP_PRESSURE_GET_PRESS () will update the data contained in the specific data structure of the pressure sensor device. The SendenvironmentalData routine then uses the corresponding call to transfer the data to the BluenRG service routine MCR_BLUEMS_F2I_2D () via Bluetooth.
Designers can use the software application provided and add a little change, or rewrite it according to their own custom needs. The Sensortile Software Environment is supported by STM32 Open Development Environment (STM32 ODE), designed to support open source software libraries and frameworks. The kit has been prepared using the St. BlueMicrosystem open frame firmware.
The open environment of the semiconductor provides developers with another significant benefit. They can utilize third-party software libraries designed to enhance function, rather than continuing to limit the specific mechanism. This feature is especially important for power-limiting IOT devices that make it particularly important in utilizing higher energy efficiency.
Reduce power requirements
For many IoT applications, the related wireless sensor systems depends on battery power and requires strict power budget. The Sensortile core system meets this hardware requirements by using low power devices. For example, at low rates usually required in environmental and motion applications, the sensor only requires a micro-level power consumption. LSM6DSM IMU only uses only 9 μA current at 12.5 Hz sample rate, and the LSM303AGR electronic compass requires only 200 μA current at 20 Hz, and the LPS22HB pressure sensor is not more than 12 μA required at 1 Hz.
In addition, the STM32L476 MCU is only 100 μA / MHz (24 MHz) in operation mode. The Bluenrg Bluetooth Transceiver IC consumes 1.7 μA in the standby mode of maintaining an active BLE stack. Even so, active wireless transmission often consumes a major power share, and Sensortile is no exception. The BluenRG transceiver transmits data at 0 dBm at 8.2 mA, which is ideal for low power applications, but even so, it is still a power-to-power consumer.
System designers can solve power consumption related to wireless communication through simple power, to reduce the number of wireless transmission transactions and shorten their duration. However, using standard Bluetooth communication, developers only have few options for restrictions. A typical application with Bluetooth features depends on device discovery and pairing using repeated polling checks, which causes a lot of power consumption and no actual data exchange. Moreover, Standard Bluetooth pairs will bring serious logistical complexity to the IoT deployment, as each IoT device needs to be placed in discovery mode. Second, it must be paired with mobile devices or other data aggregators.
The label mechanism of Bluetooth provides alternatives to eliminating power consumption and logistics issues related to discovery and pairing. Unfortunately, the standard beacon cannot carry any data payload (such as sensor data).
However, using its IT.Over.beacon technology, ENMO Technologies can combine the power saving advantages of the beacon technology to the data exchange function of Bluetooth pairing equipment technology. Therefore, ENMO's mechanism provides up to 50 kB of variable size payload, while also meets the low-power requirements required for long-term operating battery IOT equipment.
Like this Sensortile environment, developers can utilize ENMO reference firmware. Although the ENMO reference firmware is processed to maintain transparency to developers, it replaces low-level integration semiconductor calls to calls to their existing IoT.Over.beacon libraries for SENSORTILE.
To this end, developers need to use the STM32 ST-LINK utility to load the reference firmware, which provides a simple graphical user interface to select and upload files. After the ENMO reference firmware is loaded into the Sensortile core, the ENMO is connected to the ENMO's Android and iOS mobile apps through low-power Bluetooth connection. Developers can easily display Sensortile data in the ENMO application, ie, using the gadget to display the sensor data as a graphic or table (Figure 5).
A key feature of traditional Bluetooth beacons is to trigger when mobile devices enter and leave the physical area covered by a beacon function. But for IOT equipment, concepts of physical entry and exit may not apply.
ENMO provides a special mechanism to mimic the traditional entry and exit mode of the Bluetooth cursor. Here, the developer specifies the conditions triggered and exited for the IoT device. For example, a temperature detection IoT device can initiate an "entry" or "exit" protocol when the temperature changes above or below a set threshold.
Like this Sensortile package, the ENMO reference firmware for Sensortile provides an immediate solution for rapid deployment of low-power IOT devices with Bluetooth function. Similarly, for custom Sensortile development, ENMO provides a software development kit (SDK) that allows engineers to integrate ENMO's IoT.Over.beacon mechanism to their own unique Sensortile IoT applications. Using ENMO SDK, developers use the custom SENSORTILE firmware to write the SSSORTILE firmware, and call ENMO's IoT. Over.beacon library when you need to send data through Bluetooth. The library will transparently perform data transfer in IT.Over.beacon mode, and provide software callbacks after completion of the transfer.
Summarize
Battery-powered IOT design has caused a major obstacle to developers who want to quickly deploy a Bluetooth sensor device. The STAD STASORTILE development kit provides a complete solution that can be used as a stand-alone device or as a subsystem to add to an existing design. Although Sensortile has low power requirements, the standard Bluetooth protocol may quickly exhaust the battery power supply system.
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