"Developers need to meet the rapidly growing demand for Bluetooth enabled portable multi-sensor designs in various markets; But finding effective solutions has always been a challenge. In order to seize the fleeting opportunity, in addition to meeting the basic requirements for ultra-low power performance, they must also be able to rapidly prototype, evaluate and customize such designs in device to cloud Internet of things (IOT) applications.
This article will introduce ON Semiconductor System on chip (SOC) of ultra-low power Bluetooth processor, and show how the SOC or related system level package (SIP) version meets the basic requirements for battery powered design. The related evaluation board and IOT development environment can further greatly simplify the process of developing multi-sensor devices to cloud applications.
Low power Bluetooth applications
In many intelligent product applications such as wearable fitness equipment, medical monitoring equipment, lighting, locks, electrical appliances and automobiles, battery powered devices supporting Bluetooth can provide connection and processing functions. User expectations and competitive pressures continue to drive the market demand for more comprehensive applications, which need to be driven by more accurate data provided by more sensors. In some fields such as industrial applications, multi-sensor function is essential to detect movement, vibration, impact, temperature and humidity levels or other data, which are necessary to ensure employee safety, equipment status or basic asset management.
In the daily activities of users, these devices must not only reliably transmit data from multiple sensors, but also reduce the need for frequent battery replacement or battery charging. This is critical to achieving a satisfactory user experience. At the same time, the underlying solution must help reduce the cost and complexity of battery powered Bluetooth product design.
From on semiconductor NCH-RSL10-101WC51-ABG Rsl10 SOC is such a solution. It can meet the requirements of ultra-low power consumption. At the same time, it also provides a hardware foundation for SIP and evaluation board to help speed up the development of final products. The integrated solution based on rsl10 can be used with on semiconductor software for customized development, or with digi key DK IoT Studio Use together to achieve rapid development, so that developers can quickly deploy and evaluate ultra-low power multi-sensor applications.
In depth discussion of rsl10 Bluetooth Wireless SoC
Rsl10 is a Bluetooth 5 Certified Wireless SoC designed to meet the growing demand for ultra-low power design of wearable devices, mobile products and other interconnected products. Rsl10 has a set of comprehensive integrated subsystems and functional modules, which can provide a single-chip solution and meet the requirements of typical IOT devices and wearable devices supporting Bluetooth (Fig. 1).
Figure 1: the rsl10 SOC of on semiconductor integrates the processor and wireless electronic system, providing a complete ultra-low power solution for Bluetooth 5 authentication devices（ Image source: on semiconductor)
The main processing module of the device includes arm ® Cortex ®- M3 core, proprietary lpdsp32 32-bit dual Harvard architecture digital signal processing (DSP) core, complete Bluetooth 5 certified wireless electronic system - all supported by a dedicated shared memory area. In order to protect code and data, an IP module provides a mechanism to prohibit external access to the device's on-chip flash memory, random access memory (RAM) or core. In addition to a full set of standard serial peripherals, the device also provides four channel analog-to-digital converter (ADC), universal IO (GPIO) and audio interface. By using a series of voltage regulators to supply power to the internal power domain separately, the device can output a voltage in the range of 1.1 volts to 3.3 volts with a single voltage source.
Although rsl10 can support various 802.15.4 low data rate wireless personal area network (WPAN) protocols, it can still provide comprehensive Bluetooth support through the combination of built-in hardware and software. The hardware supports the construction of integrated radio frequency (RF) front end based on Bluetooth physical layer (PHY). The baseband controller works with the RF front end to provide hardware support for the packet and frame processing layer of the Bluetooth protocol stack. Here, a small built-in software kernel provides event and information processing services for RF traffic management, information exchange and timer functions. Finally, the Bluetooth library and related profile libraries run on the arm Cortex-M3 processor to form a complete Bluetooth stack of application software (Fig. 2).
Figure 2: the rsl10 SOC of on Semiconductor provides a complete Bluetooth stack by combining the software running in the arm Cortex-M3 core with special hardware (including baseband processor and underlying RF front end)（ Image source: on semiconductor)
Based on the hardware support in the RF front-end and baseband processor, the software stack combines the lower level low-power Bluetooth (ble) protocol service layer, including logical link control and Adaptation Protocol (L2CAP), attribute protocol (ATT), Security Manager Protocol (SMP), general access profile (GAP) for defining connections Generic attribute profile (GATT) for defining data exchange based on services and characteristics.
In addition to this Bluetooth protocol stack, the rsl10 profile library also supports several standard Bluetooth profiles often used in wearable device applications (including heart rate, glucose monitoring and blood pressure), rezence wireless charging profiles, man-machine interface devices (HID), and profiles for positioning, running, cycling and other applications.
High energy efficiency
Perhaps the most important advantage for designers is that the rsl10 consumes relatively little current and provides Bluetooth connectivity at a data rate of 62.5 to 2000 Kbps. The peak receive (Rx) current is 5.6 Ma with a 1.25 volt power supply (Vbat) and only 3.0 Ma with a 3 volt Vbat. When the transmission power is 0 DBM (the decibel reference is one milliwatt), the peak transmission (TX) current is 8.9 Ma when using 1.25 V Vbat and only 4.6 Ma when using 3 V Vbat.
Rsl10 achieves high energy efficiency through its architecture. In the ulpmark certification test of EEMBC, its core profile score reaches 1090 points (when using 3-volt power supply) and 1260 points (when using 2.1-volt power supply), which is at the leading level in the industry.
Developers can further improve efficiency by selectively disabling hardware modules when rsl10 is in full speed operation mode, or placing devices in low-power standby or deep sleep mode during idle. It is worth noting that rsl10 automatically adopts these power mode mechanisms to maintain ble connection between transceiver events. Therefore, the device can perform Bluetooth advertising operations on all three Bluetooth advertising channels with an interval of 5 seconds and consumes only 1.1 Ma of current.
Standby mode provides developers with an option to enter the mode after the device remains low for hundreds of milliseconds (MS) to only a few milliseconds to save power.
During standby mode, the rsl10 uses clock gating for logic and memory and reduces the supply voltage to reduce leakage current and achieve a typical power consumption of only 30 ma. Since the on-chip power supply circuit remains active, the device can return to the working state relatively quickly.
Deep sleep mode provides multiple options to significantly reduce power consumption while maintaining the ability to respond to external events. When operating in this mode, the device provides 8 KB ram hold and consumes only 300 milliampere (NA) current when using 1.25 volt Vbat and 100 Na current when using 3 volt Vbat. When in the deepest sleep mode, the device consumes only 50 Na current at 1.25 volts (25 Na current when using 3 volt Vbat) and can wake up in response to the signal received on the dedicated wakeup pin.
Integrated design
The rich features of rsl10 help developers create power optimized designs without affecting performance or Bluetooth connectivity. Its high integration helps simplify hardware design. Characteristics such as integrated capacitor eliminate the traditional external capacitor requirements, that is, 32 kHz crystal is used for real-time clock (RTC), or 48 MHz crystal oscillator is used for RF front-end and main system clock. Therefore, rsl10 only needs a few external components to complete the design (Fig. 3).
Figure 3: as shown in the above buck mode working configuration, with high integration, the rsl10 SOC of on semiconductor can use relatively few components to provide a complete design（ Image source: on semiconductor)
The device integrates multiple programmable voltage regulators to supply power to digital, memory and RF front-end modules. The charging pump provides the higher voltage level required by the analog module and flash memory. With these integrated power supply systems, the device can output voltages in the range of 1.1 volts to 3.3 volts from a single power supply.
When the voltage level is lower than 1.4 volts, the designer can use the internal low dropout (LDO) regulator to power the device. Above this voltage level, the integrated step-down converter of the device can help improve efficiency with the help of an additional inductor. The only difference between the circuit design of the two power supply configurations is that when operating in LDO mode, there is no need to use additional inductors between VCC and VDC pins, as shown in Figure 3. On semiconductor will provide printed circuit board component mounting and physical design guidelines for rsl10.
System design using rsl10
For developers who do not have time or resources to build these hardware interfaces, on semiconductor's NCH-RSL10-101S51-ACG Rsl10 SIP provides an effective alternative for customized hardware implementation of system design. The overall dimension of rsl10 SIP is 6 mm x 8 mm x 1.5 mm, which integrates rsl10 SOC, radio antenna and a full set of necessary components in a single package. Using rsl10 sip, designers can put a complete ultra-low power Bluetooth authentication hardware solution into their own design and focus on meeting customized hardware requirements.
Similarly, on semiconductor's rsl10 software package can also help them focus on customization requirements. On semiconductor Rsl10 software development kit ( SDK) is built based on ARM cortex microcontroller software interface standard (CMSIS) hardware abstraction layer (HAL), and can provide drivers, utilities and sample code distributed in rsl10 CMSIS pack (Figure 4).
Figure 4: the rsl10 software environment of on Semiconductor provides a series of services and utilities in the benchmark software package. In addition, it also provides other software packages to support the development of Bluetooth mesh network and Bluetooth Internet of things（ Image source: on semiconductor)
The software package provides more professional services, including Bluetooth support, FreeRTOS real-time operating system (RTOS) and wireless firmware update (FOTA) utilities. In addition, on semiconductor also supports more professional functions through a separate Bluetooth mesh network software package and Bluetooth Internet of things development (b-idk) software package. For example, b-idk CMSIS pack provides services related to the Internet of things, including sensor drivers, cloud connection support and related application level software samples.
To carry out customized development, software engineers only need to load the benchmark package and optional package into the integrated development environment (IDE). Rsl10 software distribution supports on semiconductor's own IDE, arm keil µ vision and IAR embedded workbench environment. After loading the package, developers can study the sample application and learn the implementation of key features.
Ble multi-sensor board that can be deployed at any time
By using rsl10 SIP and rsl10 SDK together, you can quickly start developing customized devices that support Bluetooth functions and meet strict ultra-low power requirements. However, for some applications, we may not or even need to invest the time and resources required to build custom solutions.
For example, industrial multi-sensor monitors or smart locks and light switches may require a small device that supports Bluetooth, which can also extend battery life and provide data from a variety of sensors. For these applications, on semiconductor RSL10-SENSE-GEVK The multi-sensor evaluation suite provides an immediate hardware solution. The board of the Evaluation Kit is internationally certified and can be deployed in ultra-low power applications at any time.
Rsl10-sense-gevk board includes rsl10 sip, multiple sensors and on semiconductor N24RF64DWPT3G 64 kb near field communication (NFC) EEPROM, RGB LED, programmable button. The plate occupies a circular base surface with a diameter of less than 30 mm. This base surface is only larger than that included in the kit CR2032 Button battery and flexible NFC antenna are slightly larger (Figure 5).
Figure 5: on semiconductor's rsl10-sense-gevk evaluation board combines rsl10 SIP with a series of sensors commonly required in wearable devices and Internet of things devices（ Image source: on semiconductor)
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