BLOGS!!!

Author: Mahesh Balan, Cypress Today, technology is advancing at an unprecedented pace, and devices are transforming the world into a smarter, more connected place. The emergence of new technologies has not only enhanced existing systems but also created entirely new market opportunities. One such innovation is Bluetooth Low Energy (BLE), a low-power, short-range, and low-data-rate wireless communication protocol developed by the Bluetooth Special Interest Group (SIG). BLE’s efficient layered protocol stack allows for the transmission of small data packets with minimal power consumption, making it ideal for battery-powered applications like low-power sensor networks that require periodic data collection and processing. This article explores how to effectively leverage BLE to maintain low power in wireless sensor applications where data changes infrequently. In today’s world, we are entering the era of the Internet of Things (IoT), where various systems must collect and exchange data seamlessly. BLE plays a crucial role in this ecosystem by enabling wireless connections between sensors, forming networks and facilitating data exchange between devices. A host device, such as a smartphone, can monitor and control all network nodes. IoT applications range from tracking daily activities to smart home automation, including efficient lighting, temperature and humidity monitoring, and remote control of consumer electronics. **Low-Power Bluetooth Power Modes** When a sensor is powered by a battery, minimizing power consumption is essential to ensure long operational life. BLE becomes the optimal choice in such scenarios. For example, a low-power temperature and humidity sensor, which updates data slowly, can be connected to a BLE-enabled microcontroller that processes and transmits the data to a host device. The BLE subsystem operates at a low frequency—such as once every 100 milliseconds—and enters low-power mode otherwise. Devices like Cypress’s PSoC 4 BLE offer multiple configurable power modes, allowing developers to optimize the BLE subsystem independently of the main processor. This flexibility helps reduce power usage significantly, extending battery life for years on a single charge. The system supports five power modes: active, sleep, deep sleep, sleep, and stop. The BLE subsystem, or BLESS, has three modes: active, sleep, and deep sleep. In deep sleep mode, the BLESS remains active with a current draw of just 1.3 microamps. It can send and receive data in active mode, while in sleep and deep sleep modes, it stays idle but maintains connectivity. These modes operate independently, giving developers the freedom to configure the system for maximum efficiency. With such features, it's possible to build systems that consume very little power, often running on button batteries. For instance, the average power consumption during a 1-second broadcast interval is only 26 microamps, and even lower during a 1-second connection interval, at just 17 microamps. **Sensors and Low-Power Bluetooth** Sensors can be broadly categorized into analog and digital types. Analog sensors are used for monitoring smoke, gas, ambient light, and motion, while digital sensors measure temperature, humidity, pressure, and acceleration. When integrated with a BLE subsystem, these sensors can be connected through various methods. An analog sensor might interface with a SAR ADC, whereas digital sensors can communicate via I2C, SPI, or other interfaces. Integrated timers, counters, pulse width modulators, and Universal Digital Blocks (UDBs) can further process sensor data. Once processed, the data is sent over the BLE interface for monitoring by a smartphone or another client device. As resource availability and cost vary, different BLE-enabled processors, such as PSoC 4 BLE, can be selected to suit various application needs. **Wireless Sensor Networks** Wireless sensor networks are commonly implemented as mesh or hub networks. In a hub network, all sensors are located in the same area and connect to a single BLE peripheral (server), which then sends data to a central device (client). In a mesh network, each node connects to a BLE peripheral and communicates with a central device remotely. This topology allows for extended coverage and robust communication. The built-in flexibility and rich resources of BLE-enabled processors allow sensors to interface with a single BLE device. Figure 2 shows a typical configuration using PSoC Creator, an IDE for developing applications around the PSoC architecture. The figure includes analog and digital sensor interfaces as well as the BLE subsystem, representing a common industrial data monitoring system for smoke, light, temperature, humidity, and pressure. Each component has an associated API and data table for configuration. **BLE Component Configuration** In the BLE configuration, the component is set as a slave in the GAP layer, allowing any BLE device to scan and connect to it when it broadcasts its name. In the GATT layer, the BLE device acts as a GATT server with a custom service profile. The BLE low-power feature is enabled within this component, and a single "Sensor Service" contains five features for collecting data from different sensors. Each feature includes a notification function to send sensor data. Everything in BLE is handled as an "event." The BLE stack provides a "definition" to manage these events. Below is a snippet showing some of these operations: ```c CyBle_Start(AppCallBack); void AppCallBack(uint32 event, void* eventParam) { CYBLE_API_RESULT_T apiResult; switch(event) { case CYBLE_EVT_STACK_ON: apiResult = CyBle_GappStartAdvertisement(CYBLE_ADVERTISING_FAST); if(apiResult != CYBLE_ERROR_OK) { /* Error */ } break; case CYBLE_EVT_GAP_DEVICE_DISCONNECTED: apiResult = CyBle_GappStartAdvertisement(CYBLE_ADVERTISING_FAST); if(apiResult != CYBLE_ERROR_OK) { /* Error */ } break; } } ``` Once connected, devices can send notifications with varying connection intervals. The `CyBle_ProcessEvents()` function should be called regularly in the `while(1)` loop. Data can also be sent as a notification in the same loop. Here's an example of sending one byte of temperature data: ```c void SendTempNotification(uint8 TempData) { CYBLE_API_RESULT_T bleApiResult; CYBLE_GATTS_HANDLE_VALUE_NTF_T TempHandle; TempHandle.value.val = &TempData; TempHandle.value.len = 1; TempHandle.attrHandle = CYBLE_SENSORSERVICE_TEMPERATURE_CHAR_HANDLE; do { bleApiResult = CyBle_GattsNotification(cyBle_connHandle, &TempHandle); CyBle_ProcessEvents(); } while((CYBLE_ERROR_OK != bleApiResult) && (CYBLE_STATE_CONNECTED == cyBle_state)); } ``` The processor and BLESS have independent low-power modes. If the device is disconnected, the processor can enter sleep or stop mode, while the BLESS can use deep sleep mode. Other components like ADCs or I2C peripherals can also enter their own low-power states and wake up when needed. This precise control over power allows developers to tailor energy usage based on the system’s requirements. Finally, modern BLE-enabled smartphones can scan and monitor sensor networks. Some manufacturers provide mobile apps for BLE communication, such as Cypress’s CySmart, which allows users to monitor BLE transmissions on Android or iOS devices. **BLE Beacons** BLE beacons transmit signals that can be captured by nearby smart devices. For such applications, only the BLE component needs to be configured as a broadcaster. Beacons consume minimal power and benefit from integrated processor designs. Solar-powered BLE beacons and wireless sensor nodes can also utilize BLE for communication. BLE has become a dominant force in many markets, including consumer, industrial, and embedded applications. Its success lies in its ability to operate with extremely low power consumption. BLE enables developers to create battery-powered, long-lasting, and user-friendly applications that meet the growing demands of the IoT era.

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