In a series of blogs on BLE, we have discussed in detail about the Bluetooth technology, its classifications, its popular variant BLE and various hardware design considerations such as SoC selection, RF layout and Antenna selection. These posts were primarily in perspective of hardware design.  Bringing up the software functionality is mostly straight forward as the stack is provided by the silicon vendor and will run with little or no modifications. But improving and optimizing the performance is a different story altogether. In this series of blog, we will discuss about various parameters related to BLE operations and important considerations while working with BLE devices.

To begin with, some of the important aspects of Bluetooth low energy communication are as follows,

  1. Advertisement interval
  2. Connection interval
  3. Slave latency
  4. Connection supervision timeout
  5. Data throughput

Understanding the above aspects will help any developer to lower the device power consumption, increase the speed of connection and improve the reliability of data transmission and reception.

In the following sections of this blog, we will discuss in detail about the BLE Advertisement process along with a practical example based on Embien’s eStorm-B1 Bluetooth Low Energy module by capturing the Advertisement packets using the nRF sniffer.

BLE Physical Layer

It is important to know about the BLE physical layer, such that we understand the BLE communication better, because physical layer includes the actual RF radio and is in charge of sending the signals over the air.

Bluetooth Low Energy is similar to classic Bluetooth where both of them use 2.4GHz spectrum but differ from each other with different modulation index. Classic Bluetooth uses 79 channels whereas BLE uses only 40 channels and are the channels of both are spaced differently. Due to this, the BLE and classic Bluetooth cannot communicate. But there are modules that can support both BLE and classic Bluetooth which operates by switching its modulation parameters and the channels.

The 2.4GHz spectrum of BLE is divided into 40 channels (0 to 39) which extend from 2402MHz to 2480 MHz with 2MHz spacing. Among the 40 channels, BLE advertisement takes place in 3 channels (37, 38 and 39) and data exchange takes place in remaining 37 channels.

The following image illustrates the channel layout of BLE with 3 advertising and 37 data channels.

Channel Layouts of BLE

BLE – Channel Layout

BLE Communication

BLE communication takes place between a “central device” (for example Android Smartphone or iPhone) and a “peripheral device” (for example eStorm-B1 BLE module). Any BLE communication can happen only with the following two modes,

  1. Advertisement mode
  2. Connection mode

BLE advertisement mode by default is uni-directional and will be initiated only by the peripheral device through sending advertisement packets. The peripheral device will broadcast advertisement to every device around it.

Connection can be initiated only by the central device (within the communication range of the peripheral device) to receive more information. Only in connection mode, both the peripheral and central device can send packets.

Connection cannot be done between two devices without using advertisements and central device cannot send any packets to peripheral device without a connection. 

BLE advertisement Interval

BLE peripheral device in advertisement mode will send advertisement packets periodically on each advertising channels (channel 37, channel 38 and channel 39) at a user defined interval called “Advertisement interval”. Setting advertising interval is the first and foremost task for any developer, since the value has great impact on the connection speed and power consumption. The advertising interval can be as short as 20 milliseconds or as long as 10.24 seconds.

In practical case, the time interval between the advertisement packets will have a fixed interval set by the user and a random interval between 0 millisecond to 10milliseconds. This random interval will be added automatically in order to avoid collision between advertisements of different devices.

Interval between BLE Advertising events

BLE Advertisement Interval

A short advertisement interval will enhance the central device to find the peripheral device quickly. On the other hand, due to frequent radio operation the power consumption becomes higher. So the developer should set a value balancing the speed and power consumption.

eStorm-B1 module – UART to BLE setup for capturing advertisement packets and interval

In this example, eStorm-B1 BLE module and PC communication is established via UART. UART interface is available in the module in TTL level and a UART to USB Bridge is used to connect the module with the PC via USB port. A windows console application “UART_BLE” is developed to simply the process of communications such as,

  1. Starting and stopping advertisements
  2. Transmit and receive data’s
  3. Set and get BLE RF parameters such as
    1. Transmit power
    2. Advertisement interval and
    3. Connection interval
  4. Enabling interrupts
  5. Get interrupt status

nRF Sniffer, a windows application from Nordic Semiconductor, together with Wireshark, is used for viewing the Bluetooth Low Energy communication between two devices using BLE. In this example, BLE advertisement packets sent from eStorm-B1 and the interval between two advertisements are sniffed.

The following images are the screen shots that depicts the advertisement interval of 5 seconds being set in eStorm-B1 BLE module via “UART_BLE”, a windows console application and the Wireshark capture done via nRF sniffer application for observing the advertising packets and interval.

UARTBLE Console application

Embien’s UARTBLE-Console application for eStorm-B1


Nordic Sniffer application for BLE

nRF BLE Sniffer Application


Wireshark capture of BLE Advertisement interval

BLE Advertisement interval – Wireshark Capture


BLE Tags and BLE Beacons

 BLE advertisements in general are of two types such as connectable advertisement or non-connectable advertisement. Connectable advertisement type is most common. It is not directed and it is connectable, which means a central device can connect to the peripheral that is advertising and it is not directed towards a particular central device. Non-connectable advertisement is a type used when the peripheral does not wants to accept connections and broadcast only the data in the form of advertisement.

BLE Advertisement is more popular due to its significance of broadcasting data along with the advertisement. The advertisement packets itself has suitable bytes dedicated for custom data which can be used by a developer to broad cast data. The typical application of the non-connectable advertisement is the BLE tags and beacons.

BLE tags are mainly used for asset tracking were the advertisement data broadcasted will help to track each device to which they are connected.

Beacons evolved with the introduction of Apple’s iBeacon, targeted for proximity market such as shopping malls, retail showrooms, etc. Also we have Google’s Eddystone as an alternative for iBeacon for Android platforms. In both these technologies the device will transmit very small bits of data via BLE advertisement.

Application of BLE Beacons

BLE Beacon – Applications

In this blog we have briefly discussed about the BLE communication, BLE advertisement and advertisement interval. In the fore coming series of blogs, we will discuss in detail about the BLE connection parameters such as connection interval, slave latency, etc.

About Embien

Embien Technologies is a leading provider of embedded design services for the Semi-conductor, Industrial, Consumer and Health Care segments. Embien has successfully executed many projects like based on IoT such as healthcare Wearables, Gateways, and Data Analytics etc. Embien also offers a set of wearable design collections complete with electronics, firmware and Cloud that can be used to shorten product development costs and time significantly.

Saravana Pandian Annamalai
30. May 2017 · Write a comment · Categories: Embedded Software, Sparklet GUI Library, Technology · Tags: ,

Embien has been working on various types of embedded systems including those powered by FPGA’s for a variety of applications. Of late, there are a lot of requirements for GUI Application development on FPGAs for user interaction. In this blog, we introduce our Sparklet embedded GUI library along with our Flint FPGA UI Interface Editor for enabling FPGA for graphics. Also Sparklet running on a Linux powered Intel Cyclone V SX SoC FPGA is demonstrated with a Terasic DE1-SoC-MTL2 kit.

FPGA GUI Application Development

Modern FPGA’s have a multitude of IPs to handle different peripherals interfaces. Most of these FPGAs, called SoC FPGAs have an internal microcontroller core as a hard IP around with LEs are placed for configuration and customization.

Such a design warrants a powerful user interface for communication with the user for a seamless experience. Full fledged Intuitive GUI application development ecosystem is the need of the hour to enable a faster time to market. Developers need to dedicate their effort on FPGA and internal logic developments rather than working on nitty-gritty of FPGA GUI application development.

Sparklet – embedded GUI library is the right fit for such a FPGA based GUI development. Written purely in ANSI C, Sparklet can be ported across platform with minimal effort. The GUI Application development can be done using our Eclipse based Flint tool that supports Windows based emulation as well. The FPGA UI Interface Editor tool generates ‘C’ source files and headers that can be compiled in to the project to get a fully working application within a very short time.

Sparklet being a very modular and extensible design, it is also possible to take advantage of the Graphical acceleration engines with Sparklet to improve the rendering speed and quality.

Sparklet GUI on Intel Cyclone V FPGA

This demo of the Sparklet GUI library runs on a Intel Cyclone V SX SoC FPGA. Some of the salient features of the FPGA include

  • Dual-core ARM Cortex-A9 (HPS)
  • 85K programmable logic elements
  • 4,450 Kbits embedded memory
  • Fractional PLLs
  • Hard memory controllers
  • Multiple display interfaces
  • Multiple USB Host interface
  • Ethernet, UARTs, ADCs etc

The development kit from Terasic, DE1-SoC-MTL2 includes a DE1-SoC development board targeting Altera Cyclone® V SX SoC FPGA, along with a capacitive LCD multimedia color touch panel which natively supports five points multi-touch. The display is a 7-inch TFT LCD with pixel resolution of 800*480 and color depth of 16 million colors (8-bit RGB) along with a    LED backlight.

For such an FPGA based design, the underlying software can be designed with any of the following architectures:

  • Without an OS
  • With a minimal RTOS
  • With full fledged OS like Linux

Sparklet, providing design flexibility, is suitable for use with each of these approaches. The below demo showcases Sparklet running on top of Linux OS.

Though none-of the underlying Graphical engine features are not used in this case, it is possible to do so using the hardware acceleration engine changes.

Thus Sparklet along with Flint makes FPGA GUI application development a lot easier and enables developers work on core functionality there by reducing overall product development time.

About Embien: Embien Technologies is a leading service provider in the Embedded software domain. Our team has rich experience in working with various OS like Linux, Android, Windows CE, FreeRTOS, uC-OS, QNX etc. Learning from our experiences in various application domains, we have conceptualized and created the Sparklet Embedded GUI tool that can be used to develop UI’s faster and smaller.

Smart Metering

Today things are made smart and processes are becoming smart which enhances the life style of humans in many ways. One such example is the “Smart Metering”. All over the world, the mechanical energy meters are replaced by digital energy meters and currently advanced to smart meters which provide accurate results for greater period of time.

Digital energy meter is an electronic device that measures and stores the consumption of electric energy periodically and communicates the stored information to the provider (utility) via wired communication (Optical port, serial communication) as well as wirelessly for monitoring, analysis and billing. The wireless energy meters are referred as Smart Meters and most commonly used in industrial segments for various reasons and low end energy meters (wired communication) are used in domestic, commercial segments which supports digital interface such as RS232, RS485 serial communication.

Advanced Metering Infrastructure

Since the smart meters include wireless communication such as GSM/GPRS, low power radio, etc the readings can be updated in the central database from anywhere in the world and facilitates the customer (User) with plenty of information’s such as daily usage, peak demand, last interval demand, load profile, voltage profile, sag and swell events, phase information, power factor, tamper notifications, etc. This type of system is named as “Advanced Metering Infrastructure“(AMI). Such a huge amount of information is more important in building a smart grid by which the amount of power generation can be predicted based on power demands.

Automatic Meter Reading

Smart meters with AMI system are more advanced and expensive which makes them overrated for domestic segments. Similar to the “Advanced Metering Infrastructure” (AMI), Automatic Meter Reading (AMR) system is available as an automated way to collect basic meter reading from low end energy meters that are widely used in domestic segments where a system is required for collection only. AMR includes a handheld reading entry device where data from Smart Meters is acquired by connecting the device to the digital ports typically RS232 or RS485 serial ports using dedicated serial cables. The technician will have to plug these cables to the meter of concern and the handheld device will acquire the readings automatically. Likewise the technician will acquire data from each and every meter of his zone and the acquired readings are transferred to the central database for billing.

Though AMR has become common way of reading meters, it can be made more advanced. At present there are many wireless technologies available for small data transfer at very low costs. Among the various wireless technologies, BLE is the most popular. With the BLE enabled smart phones together with an Android app will simply replace the handheld AMR system which performs the similar functionality with wireless operation. Also a tiny BLE module with serial interface (RS232) like eStorm-B1 is sufficient to enable wireless connectivity for the energy meters.

Smart Metering using eStorm-B1 BLE Module

In previous blog, we have discussed in detail about eStorm-B1 BLE module application as a UART to BLE Bridge with a brief demo video. In this blog, we will demonstrate a Smart Metering application which can be realized by interfacing eStorm-B1 with energy meter via RS232 interface and by replacing the traditional handheld reading device with Smart AMR Android app running in Android smart phone with BLE connectivity.

The following video shows the demo of Smart Metering application,

In this demo, a digital energy meter is upgraded to a smart meter by adding eStrom-B1, an NXP KW31Z based BLE module via already available RS232 serial interface. In the other end, an Android Smart phone is equipped with a custom designed Android application “SMART AMR” which will communicate with the smart meter via BLE connectivity and acquire the reading when required.

The following are the features of Smart AMR Android application,

  1. Secured login – User name and password protection for authorized person login only
  2. Area selection – User configurable settings for selecting region, circle and section of his/her zone
  3. GPS based location mapping – Automatic mapping of the user’s present location
  4. One touch reading acquisition – Complete list of available registered meters in the particular location with complete details such as consumer name, ID, meter number, phase, load information and one touch acquisition of old, new reading and energy consumption.
  5. Auto update – Automatic update of acquired readings to central database via available 3G/4G connectivity in Smartphone.

This type of setup is very much suitable for AMR systems which can replace the handheld systems with the low cost smart phones and can reduce the burden on technicians by reducing more physical works that are present in the current handheld systems.

About Embien: Embien Technologies is a leading provider of embedded design services for the Semi-conductor, Industrial, Consumer and Health Care segments. Embien has successfully executed many projects like based on IoT such as healthcare Wearables, Gateways, and Data Analytics etc. Embien also offers a set of wearable design collections complete with electronics, firmware and Cloud that can be used to shorten product development costs and time significantly.