The entry-level class: M0 core systems
A small ARM Cortex M0 or M0+ core is sufficient for many applications. It enables measurement data to be transferred to the Cloud in order to make wear assessments and carry out remote adjustments. With over-the-air updates, firmware, wireless stacks and application code can be updated in response to new legislation, bugs or security threats, including in after-sales.
The smartphone is often the first point of access to the Internet. An energy-efficient option for it is the Bluetooth Low Energy (BLE) interface. The following one-chip wonders are a popular choice in implementing it:
The market leader in BLE interfaces is Nordic Semiconductor's nRF51822. The product family is available with 16 or 32kB RAM, with 128 or 256kB of flash memory, and in a QFN or WLCSP package. The hardware is designed for low power consumption, and is backed by the company's in-house Bluetooth stacks, lots of application-specific SDKs, and outstanding support. The success of this IC family and its extensive software is also down to the module manufacturers:
Fujitsu's nRF51822 based modules are targeted more at customers with higher production ambitions.
Dynastream's nRF51422 uses the big nurse call of the nRF51822. So the modules of the N5 family additionally support the SoftDevices S210 and S310. While the S210 protocol is a pure ANT stack, the S310 is the corresponding multi-protocol variant for simultaneous use of ANT and BLE. This is useful to connect a power-saving ANT mesh network to an Apple iPhone which itself does no support ANT.
RF Digital markets the RFduino family alongside the naked nRF51822 variants. The RFduino family features a pre-installed S110 SoftDevice, with a software layer configured above it which simplifies the control of BLE and the GPIOs. In this way, actuators or sensor devices can be implemented with just a few lines of code. A rule applicable to all BLE applications is that custom apps have to be programmed for different smartphone operating systems. That is not the case with the SIMBLEE nRF51822 module: The associated app is programmed once, and stored in the wireless module. All that is necessary is to install the SIMBLEE app, which imports the actual content from the module, from the smartphone operating systems' stores.
The newest addition to the Rutronik linecard is Insight SiP with its system-on-module solutions based on the nRF51822. At just 8x8mm in the LGA package, the ISP1302 modules even have a built-in antenna.
The latest releases of the TC35678 and TC35679 ICs from Toshiba focus on an ultra-low-power variant. At 3V operating voltage, they consume just 3.6mA in TX mode and 3.3mA in RX mode.
Microchip/Atmel's SAM B11 features 128kB of RAM and a 256kB flash memory.
With an in-house 16-bit core clocked at 32 MHz and delivering 41 DMIPS processing power, the RL78/G1D family by Renesas is playing in the same league. Four variants are available: SoCs with 128kB, 192kB and 256kB flash and an SoM based on the 256kB flash IC.
For more demanding needs: M4 core Systems
With an EEMBC CoreMark rating of 215 - meaning 65 CoreMarks per mA, or 3.36 CoreMarks per MHz - the nRF52832 is likely the most efficient BLE SoC at present. In a 6x6mm 48-pin QFN or 3.2x3.0mm WLCSP package, it is designed for easy processing and comes in a highly compact form factor. With battery-friendly supply voltage from 1.7V and adjustable transmission power between +4dBm and -20dBm, it is suitable for larger ranges as well as for security-critical applications which require a short range.
The nRF52832 is increasingly being used in developments for which an nRF51822 would sufficient. Arguments in favor of that include the integrated balun filter and the built-in NFC transceiver for Bluetooth fast pairing. In terms of external components, only 11 passive components and one 32MHz quartz crystal are required!
There are also SoM variants alongside the SoC. They come pre-certified, normally for Europe, the USA and Canada. The Dynastream D52 series based on the nRF52832 also offers certification for Japan, Australia, New Zealand and Korea. Although both quartz crystals and a printed antenna are built-in, the module measures just 14x9.8mm. Users willing to sacrifice an additional 20x20mm on their PCB can also opt for the variant with 30 GPIOs or integrated 3-axis accelerometer.
Telit and Fujitsu also make modules based on the nRF52832. As in its cellular series, Telit relies on a family concept for its Bluetooth modules: The new BlueMod+S42 with 10x17mm is compatible in terms of form and pins with the older BlueMod+S and BlueMod+SR models, and also has the same software interfaces. The FWM7BLZ20 from Fujitsu, at 15.7x9.8mm and featuring 5.4mA power consumption, is not only small but also an ultra-low-power module.
The ISP1507 module from InsightSiP impresses with a built-in antenna, and has a footprint of just 8x8mm.
Redpine Signals likewise uses an ARM M4 core, but adopts a different approach in terms of connectivity: The WiSeMCU family also supports conventional Bluetooth EDR, ZigBee and dual-band WiFi in addition to BLE. All the protocols and application profiles of the various wireless standards are already integrated, so the 128kB SRAM and 1MB Flash memory is generously dimensioned. Users for whom the 21x15mm RS10003-NBZ-D0M with all the peripherals is too big will find a lower-cost variant in the RS100002-NBZ-S0M, without 5GHz support, but featuring 104kB SRAM, 512kB Flash, and in a slim 14x15mm form factor. Both versions can be specified without ZigBee, WiFi or Bluetooth 4.0DM. That is not only more cost-effective, but also saves on available storage space.
The professional segment: Atom core systems
Intel is demonstrating more and more benefits in the application of its x86 core architecture. The tried and proven command sets familiar from Pentium times are now also being used in small microcontrollers down to the scale of the Quark family. Now Intel is unpacking the jackhammer, presenting the Joule: an SoM based on a 1.5GHz and 1.7GHz Atom core. With up to 8 gigabytes (!) of RAM and 16GB of flash memory, WiFi, BLE, HDMI, USB 3.0 and pre-installed Linux Distribution, the compact 24x48mm module offers the power for real-time 3D modeling, people tracking, human interaction, and object recognition tasks. There is connectivity based on WiFi and Bluetooth integration, but local computing power can significantly reduce the data traffic up to the Cloud in many applications. Joule is even suitable for building drones, robots, VR headsets, data-gloves or intelligent gateways.
For individualists: Multi-chip Do It Yourself
All SoC and SoM systems have one thing in common: they are never perfect. Something is always too much - be it the peripherals, the computing resources, the certification, or the software in the memory. So ultimately customers are paying for features they don't need. A technically perfect solution is always a custom one. That is true in relation to the hardware configuration and the wireless protocols. In terms of hardware, the ballast is accepted in order to save on certification costs and time to market. In a radical Do-It-Yourself implementation of a high-frequency design,100 man-years and more would rapidly be accumulated. That is something which corporations can little afford nowadays.
Thumbs-up for SoC and SoM
State-of-the-art SoCs and SoMs offer enormous savings, and developers are able to focus fully on their application-specific core tasks. As the single-chip solutions market grows, the scalability of the component choice is also improving. What is ultimately the best chip choice depends on the specific tasks at hand, so across-the-board recommendations are useless. What certainly is a useful idea is to consult an expert from the Wireless Competence Center.