Before looking at the ATBTLC1000-XPro Bluetooth Low Energy extension board, here is a quick introduction to the ATBTLC1000 wireless microcontroller that it uses. This SoC device comprises an ARM Cortex-M0 microcontroller, a 2.4 GHz wireless transceiver, 128 kB of RAM, 128 kB of ROM, along with both AES-128 and SHA-256 hardware accelerators. In addition, the device offers a comprehensive range of GPIO and serial connectivity of Master/Slave SPI, I2C Master/Slave and UART interfaces. The device also features an integrated DC/DC converter and power management unit (PMU) that together aid the SoC to achieve a number of ultra-low-power profile modes. A single-channel 11-bit ADC, four PWM ports and general-purpose timers are also included. The ROM is used to store a qualified Bluetooth Smart protocol stack (Bluetooth 4.1) that includes L2CAP service layer protocols, security manager, attribute protocol (ATT), the generic attribute protocol (GATT) and the generic access profile (GAP). Application-specific profiles include proximity, thermometer, heart rate and blood pressure. Figure 1 shows the block diagram of this SoC device.
Capable of operating off a battery supply in the range 1.8 to 4.3 VDC, the device consumes down to 1.1 μA in deep sleep mode, with RAM retention and RTC running, up to a peak current of 4.0 mA when in receive mode using a 3.6 V supply.
Figure 1: ATBTLC1000 block diagram.
Many IoT applications will require a battery-powered device than can operate with a minimum number of truck-rolls to replace the battery. While inconvenient in an urban environment, the impact of this with IoT sensors in extremely remote and often hazardous locations, the expense incurred due to poor battery life is significant and potentially brand damaging for the sensor manufacturer. With an innovative power architecture, the ATBTLC1000 has eliminated the need for external regulators and off-chip components. The PMU block includes a high efficiency, typically 83%, DC/DC buck converter and low drop-out regulator (LDO) to convert battery voltage to power the BLE core and the RF transceiver.
Figure 2: Atmel ATBTLC1000 Xplained Pro extension board.
Atmel’s family of Xplained Pro boards provides an extremely fast and convenient route to commence a new microcontroller-based design. Supported by Atmel’s integrated development environment platform, Atmel Studio, together with the Atmel Software Framework (ASF), a comprehensive set of board support drivers, code examples and documentation, Xplained Pro boards are available across Atmel’s AVR- and ARM-based microcontroller product families. Extension boards, such as the ATBTLC1000 illustrated in Figure 2, use a standard connector header to provide an easy way to incorporate various forms of connectivity including wired and wireless, capacitive touch sensing controls, extended IO, and a range of MEMS-based sensors. Designed with the engineer in mind, they not only speed time to market but also give confidence in the design based on the well documented materials and application notes that are available for each board.
Figure 3: ATBTLC1000 smart link controller to host diagram.
Atmel’s API follows a straightforward programming model that typically contains three operation groups, these being platform/link controller initialization, device configuration, and
The ATBTLC1000 Xplained Pro incorporates the FCC and ETSI pre-certified wireless SoC in a module package, a digital temperature sensor, debugger header support (UART, I2C, and current measurement), and a 32 kHz crystal. It can be connected to a number of host MCU Xplained Pro boards. To make things even easier, the extension board and an Atmel SAML21 Xplained Pro board are available as a complete kit or you can buy the MCU board separately.
Getting started with any Xplained Pro platform couldn’t be much easier. Before starting you need to download the free of charge Atmel Studio (currently version 7) from the Atmel website. The Atmel Software Framework is part of the download so you’ll get ready to use code examples, too. Once installed, launch Atmel Studio and connect the extension board to your microcontroller board. Atmel Studio will automatically detect which MCU and extension boards are connected and show a landing page for the combination that provides relevant documents and datasheets along with the option to launch the Atmel Software Framework to access example applications.
Figure 4: API programming model – application flow.
The operation of the API is best illustrated by use of a scheduling diagram: see Figure 5. In this example, that of setting up GAP advertising, the process means that the peripheral will issue a unidirectional broadcast data over the air in order to be discovered by
As mentioned above, the ATBTLC1000 SoC features a Bluetooth Smart Link Controller that facilitates the host microcontroller to perform all the standard Bluetooth server and client operations such as GAP and GATT. The SoC provides all the BLE 4.1 link layer and application profile functionality via the on-chip firmware. Atmel provides an Adapter API to enable host communication with the link layer firmware.
Figure 5: Scheduling diagram of GAP advertising process.
The operation of the API is best illustrated by use of a scheduling diagram: see Figure 5. In this example, that of setting up GAP advertising, the process means that the peripheral will issue a unidirectional broadcast data over the air in order to be discovered by another Bluetooth device. In addition to the required advertising data, such as device name and ID, additional information can be communicated that might assist in making a connection.
This additional data is call response data. After the initialization function at_ble-init() the advertising data needs to be set within theat_ble_adv_data_set function prior to making the call to the advertising function. If the intention is to advertise and then establish a connection, then you call at_ble_adv_start(connectable). The code example in Figure 6 illustrates just the first part of an application that starts this process from defining and setting the device name, initializing the device, setting the advertising response data and then commencing advertising. This is just an example of the simplicity achieved by using Atmel’s Bluetooth API when designing an application. More information can be found within the noted reference sources.
Figure 6: Code example illustrating the first part of an application.
For designers about to embark on developing a battery-powered IoT application, such as a temperature sensor, provisioning ultra-low-power communications is essential. Faced with having to learn and comprehend the Bluetooth protocols can be a significant challenge and may well occupy a major part of such a design. With the ATBTLC1000 Xplained Pro expansion board, Atmel has made the task extremely straightforward. The embedded developer can incorporate Atmel’s Bluetooth API function calls within the IoT application making the task quick and simple. With its FCC and ETSI radio regulatory approvals and compliance to Bluetooth SIG standards, the ATBTLC1000 is ideal to be incorporated into your design wherever it may be used.
https://www.digikey.com/en/articles/techzone/2015/dec/speeding-the-design-of-bluetooth-connectivity-for-iot-applications
