Dialing the Right Designs for Mobile Accessories

What are the new technologies in the arena?

The fast growing mobile market is fueling the demand for new accessories. In this arena, designers must consider new technologies and standards. Among the emerging applications are sports and fitness devices, portable medical instruments, home automation, and automotive and industrial diagnostics.

To get a handle on the market, Semiconductor Manufacturing & Design separately caught up with Lee Koh, mobile accessory group marketing manager at Microchip Technology; Sam Toba, director of business management at Maxim Integrated Products; and Dave Freeman, a fellow and chief technologist for power supply solutions in the Power Management business unit at Texas Instruments.

SMD: What are the biggest challenges faced by accessory developers?

Koh: There are many challenges. Some of them include the physical interfaces to the mobile device, firmware/SDK, power consumption, applications/user experience, and certification. The physical interfaces connect the accessory to the mobile device and then transmit data-oriented protocol between the electronics. They can be wired (i.e., USB) or wireless (Bluetooth or Wi-Fi).  The physical interfaces involve connectors, and sometimes proprietary information, such as iPhone 30-/8-pin connectors and its hand-shaking protocol.  The firmware/SDK is an integral part of the interfaces.  It manages the accessory over the mobile device, interacts with the mobile device OS (i.e., iOS, Android) and presents an API to the apps.  Getting the physical and SDK interface functionality to work properly requires significant coordination between the firmware engineer and electronics engineer.  In addition, a low power design is fast becoming a demand. If the accessory is correctly designed, it shall only consume a fraction of the power from the smartphone/tablet, and doesn’t wear out the battery life. Hence, designing with low power electronics (i.e. microcontrollers), and balancing the data-bandwidth and app responsiveness are critical to achieving the best power consumption requirement for an accessory.

Toba: We usually see single Li+ powered accessories, often with USB connectors.  These usually require some sort of a charger.  If it’s a complex piece of equipment/accessory, it would have a microcontroller plus a display.  In this case, a PMIC would be required.  We also sometimes see LTE dongles that have big batteries.  I would say the biggest design challenge is to keep costs low even when integrated solutions aren’t always available. Customers also often have a need to minimize heat when charging up the battery in a very small enclosure.

Freeman: The interface protocols are pretty much dictated by the host device: notebook, pad computer and smart phone. The biggest challenges for accessories include data acquisition (e.g. from sensors), data processing, power and energy management and communication.  While most of the accessories support charging over a micro-USB connector of the accessories, typical mobile host devices are not ready to share their precious energy with an accessory.  Wired charging is not the friendliest user experience.  Wireless charging is therefore becoming more popular for these devices. In the context of upcoming wireless protocols, interoperability is a challenge.  Additionally, wireless connectivity such as Bluetooth Low Energy is becoming more sought-after to easily interface to the many smartphones and tablets that include the technology. However, many accessory developers lack the RF hardware and software knowledge to integrate wireless connectivity into their devices and need easy to integrate SoCs.

SMD: What else is required?

Koh: To ensure the accessory is of the highest quality and provides the best user experience, the developers must produce compelling industrial and mechanical designs, develop a seamless interaction between the hardware and software, and finally produce an app that is attractive to end users.  Each of these tasks is challenging on its own, but they become interrelated when a smartphone/tablet accessory is developed. Each platform has its own custom certification process.  For example, accessories made for an Apple Made-for-iPod program require Apple’s certification and approval to ensure the accessory doesn’t interfere with the phone or vice versa.  Standards approvals, such as Bluetooth SIG and FCC are required if Bluetooth technology is used in the accessory.  Individually, these approvals are time-consuming and often capital investments are required. Such a design project is a complex endeavor that requires the efforts of a cross-disciplinary team.

SMD:  What are the emerging and future technology trends?

Koh: Future trends include Apple Made-for-iPod standards/specs, wireless technology embedded in the smartphone/tablet, customized phone manufacturers’ standards such as Samsung Allshare and HTC Connect. We don’t believe there is a complete shift to 32-bit MCUs to support all accessories.  We believe 32-bit MCUs are more applicable to data-intensive applications, audio and video, while 8-/16-bit MCUs are more applicable to control-related applications and low power consumption.

Toba: Most of our customers want to charge their accessories as quickly as possible with as little heat generation as possible.  Enumeration and adaptor type detection capability are important features.  For in-car accessories such as navigation systems, I’ve also seen a need for autonomous safe charging capabilities, where charge current and battery regulation voltage is controlled as a function of temperature.  We also expect wireless charging to become a big trend.

Freeman:  The future trends are towards more application-specific CPUs, combined in single SOCs.  Not only do these specialized processors provide higher performance, but at a lower power.  Low power is a key enabler for accessories. Battery technology is also key. New batteries that include silicon can add additional runtimes at approximately 25%. Other areas of innovation include wireless charging, sensor fusion/aggregation, richer data exchange and user experience (HD video on smart phones), higher end cameras and projector capability.  While late compared to Android and iOS, it will also be interesting to see how Microsoft innovates and the traction it could get from its Windows platform.

SMD: What are the emerging and future applications in the accessory world?

Koh: Smartphone/tablet computing speeds and capabilities have been advancing at an exponential rate. Wireless technology is redefining the audio market. The speaker dock and the sound bar categories have seen growth due to mobile devices and streaming services. The recent addition of audio support on Android OS 4.1 will further accelerate the adoption of consumer audio. It is also believed that medical and fitness applications will fuel the growth of the accessory market.

Freeman: Sensors are certainly part of the emerging accessory market.  Other emerging applications include smart home control and monitoring.  Industrial sensor control and monitoring and consumer device interaction (e.g. with smart TVs) are also emerging.

SMD: What hardware interfaces are available for accessory developers?

Koh:  WiFi, Bluetooth, and USB are the major interfaces. USB presents itself in both USB host and USB peripheral formats depending on the target device. Devices that fully implement the USB Battery Charging (BC) specification are likely to increase in the near future.  More phones/tablets are requiring more than 500mA to charge, which will require devices to start using the USB Battery Charging specification to draw larger currents. The USB BC spec is already being used by dedicated USB charging wall converters.  These types of devices are called Dedicated Charging Ports (DCPs).  There is another type of device called a Charging Downstream Port (CDP), which allows both high charge rates as well as full communications.  The first stage of detecting a USB BC port is the ability to distinguish between a DCP and a CDP.  This first step is called primary detection in the specification.  There are two ways after primary detection to determine if the port attached is a DCP or a CDP.  The first is by just trying to enumerate and seeing if communications is also possible.  The second is a process that requires additional hardware/firmware called secondary detection.  Currently, many phones/tablets assume that they are connected to a DCP if the primary detection returns a positive result, thus never communicating to a CDP. The end result is a phone/tablet that can either charge at a high rate, or communicate, but can’t do both.  This doesn’t work well for dock manufacturers.  These types of products need to both charge at the higher rate to quickly charge the phone/tablet, while still communicating to perform their specific function (i.e. audio, data back-up, data synchronization, etc.). Microchip offers products on both sides of the problem to help phone/manufacturers develop BC capable charging ports that also communicate, as well as the USB peripheral side to detect which type of port they are connected to.  An even more interesting possibility in the future would be for phones/tablets to adopt the USB BC Accessory Charger Adaptor (ACA) implementation.  In this configuration, the phone/tablet could be the USB host, but still draw a charge from the dock. This would allow a phone/tablet to be docked and charging with standard USB devices attached, such as a keyboard, mouse, printer, speakers, etc.

Freeman: The focus for accessories seems to be wireless connectivity for both signal and power.  ZigBee and Bluetooth Low Energy are two interface technologies that are becoming very important for future accessories to connect them to smartphones and tablets or larger home and smart grid systems. NFC is also gaining traction especially for BT pairing and WiFi handover, as well as payment applications today.

SMD: What are the important things to know in developing accessories?

Koh: For Android, some phones/tablets do not support a USB host.  There is an Android Open Accessory protocol (AOA) for those devices that allow accessory developers to enable accessories with these devices.  This library, however, is not available on all Android devices and can be added/removed by the manufacturer of the device.

Toba: It will really depend on the type of accessory.  Quick turn design will be important. Being able to leverage reference designs will help.

Freeman:  It is important to manage the energy to provide acceptable battery run-time.  Making the proper trade-off at the system level is important. 

SMD:  What resources are available to create accessories?

Koh: Microchip offers low power MCUs, firmware examples, source code, apps, demo boards, and specialized design partners to help customers create their accessories.

Freeman:  Reference designs, including antenna possibilities and regulatory compliance pre-testing, are available.  Finally software stack/examples are also a key to complete the user experience.



Mark LaPedus has covered the semiconductor industry since 1986, including five years in Asia when he was based in Taiwan. He has held senior editorial positions at Electronic News, EBN and Silicon Strategies. In Asia, he was a contributing writer for Byte Magazine. Most recently, he worked as the semiconductor editor at EE Times.

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