How to design and develop impressive wireless products

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Dilin Anand and Abhishek Mutha of EFY spoke to Badri Kothandaraman, Executive Vice President of Data Communications Division and head of Cypress Semiconductor India about wireless USB, Bluetooth 4.0, benefits of using Programmable System on Chip PSoC® and much more. Read on to find out the interesting technologies in the wireless and USB space.


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Badri Kothandaraman

Q. When devices are wireless, design and testing presents an array of new and varied challenges to the test engineer. How do you manage these challenges?
A. First, a significant Design For Testability (DFT) needs to be built into the chip. We need to have built-in self-test (BIST) where the chip is capable of testing itself. Testing RF is always tricky. In the last 2 years, we are doing pre-silicon validation platform (PSVP) testing. This means we model/ mimic the chip as close as possible and build a real interface to the external world. PSVP is challenging to create – for analog circuits, a test chip is needed and for digital circuits, RTL can be ported into an FPGA. There are limitations on PSVP, but it helps to get rid of the obvious or mundane issues and allows more efficient silicon debug to focus on real issues. It is also possible with a well-constructed PSVP, we can test for all kinds of interference and do interoperability testing on multiple OS systems. Once this is done, the firmware algorithm can be tweaked and algorithms fine-tuned with respect to frequency hopping, for example. We are pretty disciplined about not starting silicon, until we do a good job on PSVP. However, PSVP can only help upto a certain extent. When we design-in wireless USB parts at customers, issues at each customer are usually different. For example, wireless USB is a proprietary 2.4GHz and there is no standardized way of designing the antenna. The inter-operability and interference criteria are also different for each customer. On the other hand, it will be relatively easy to design with Bluetooth low energy, as it is standards-based technology and there will be no dongle design as the hosts (laptops, tablets, smart phones) have the radio embedded in their RF combo chip sets.

Q. How difficult is it to integrate low power, reliability and interference immunity into wireless products? What are the design challenges faced?
A. Integrating analog and digital into the same chip is always a design challenge. Substrate noise is a very big challenge and we need to isolate switching blocks from analog blocks. On the other hand, with the latest advances in technology, CMOS Low Power RF is now possible. Consider the WirelessUSB™ NL from cypress (http://www.cypress.com/?rID=54419) chip that consumes only about 15/18 milliamp in TX/RX communication. While meeting power requirements is a modest challenge, signal loss or report loss due to interference is a real issue. To deal with it, there are common design techniques. One of them is frequency hopping to move from one frequency to another. Another technique to counter interference which was used very successfully in Cypress first generation radios was DSSS (Direct Sequence Spread Spectrum) where the transmitted signal has a higher bandwidth in order for it to be more robust.

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Q. Could you elaborate more on wireless USB and its applications? Is there an alternative to it?
A. The most common application of wireless USB is a wireless mouse with a dongle attached to the PC via USB. Cypress is into such human interface devices such as wireless mice, keyboards, remote controls, wireless trackpads and toys. These are all proprietary protocols in 2.4GHz RF, so each design is custom. However, the future is going towards Bluetooth low energy (BLE) which is a standard-based technology, still in 2.4GHz range. This means that a USB dongle is no longer required, as BLE capability would be built into the combo-radio chipsets inside the hosts. The BLE mice would directly communicate to the combo-radio chipsets inside laptops, phones, tablets.

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Q. With respect to the Wireless USB solutions, how can a design engineer incorporate them in his design? How will it assist him?
A. If a design engineer wants to connect something to the PC wirelessly, all he needs to do is add short –range low power connectivity by using our wireless chips at each end. For example, consider someone who wants to transfer data from UART to PC with a wireless link. He could use one of our enCore series MCU’s to convert UART data into a SPI format (Serial Peripheral Interface) and our radio chip takes the SPI data and transmit it to the other end over a 2.4GHz link. At the other end, there is a nano-dongle with a USB MCU which provides PC connectivity. However, note that transfer at high data rates (>1 Mbps) is not feasible with this technology as it is for control signals only, communicating state information. That’s the limitation, it is not the same as Wi-Fi. The emphasis is totally on low power.

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Q. With respect to Bluetooth 4.0, you mentioned that it would not require a dongle. Why is that limited to Bluetooth 4.0 and not possible in the previous versions?
A. Of course, it is possible in the previous generation too, but Bluetooth 3.0 is more power-hungry and has a higher throughput than Bluetooth 4.0 (also called BLE). The real throughput of Bluetooth 4.0 is as low as 0.3 Mbps, so it is not designed for data-heavy applications but it is designed to only transfer control signals, communicating state. The connection efficiency in BLE is maximized and very short (3ms) compared to standard bluetooth for achieving the ultra-low power. Majority of these BLE peripheral devices are envisioned to have coin-cell batteries only as they are going to be in sleep mode greater than 95% of the time.

Q. Considering Cypress is into USB controllers, what is the most exciting development happening here that would interest system designers?
A. The most exciting innovation today is USB 3.0 where the speed of transferring data is about 5 Gbps. Cypress has a USB 3.0 product called FX3, which plays in the peripheral device segment. What I mean is we don’t play in the PC with FX3, but we help adding USB 3.0 5 Gbps connectivity to any device that connects to the PC. Common devices where FX3 goes in are industrial cameras, gaming systems, document scanners, video-conferencing equipment, surveillance cameras etc. One end of FX3 connects to the PC USB 3.0 port and on the other side we connect a parallel interface. Most image sensors do have a parallel interface and FX3 can flexibly connect to this parallel interface via GPIF (general programmable interface). If you order one of our FX3 development kits and use one of our example projects, you can make the FX3 chip connect immediately to the image sensor and have data flow from image sensor to the PC in minutes, enabling seamless video streaming on the PC.

Q. What would be the major differences between USB 3.0 pipe in a video sensor compared to that of say a couple of sound sensors? Is there a difference in the hardware that you implement in these peripherals? What about video transfer with USB 3.0 ?
A. No, the hardware is the same but people do not use audio yet for USB 3.0. At this point, USB 3.0 is primarily for high-definition imaging. The USB-IF (USB Implementers’ Forum) is working on what is called AV – Audio Video with USB 3.0. There is no standard protocol yet and we are working with USB-Implementers Forum (USB-IF) to come up with that as well. Until that point, it is proprietary.

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About Cypress India

Cypress has been operating in India for more than 15 years. The company has 650 employees in its Bangalore office, including half of its global design engineers. Cypress is unique among multi-national semiconductor companies in that it conducts all aspects of product development in India, including design engineering, product engineering, testing and characterization, applications engineering, software development, IT, strategic marketing, marketing support, planning, operations and finance. Cypress offers Indian professionals unparalleled opportunities to grow careers in a variety of areas, unbounded by geographical barriers

About Cypress
Cypress delivers high-performance, mixed-signal, programmable solutions that provide customers with rapid time-to-market and exceptional system value. Cypress offerings include the flagship PSoC 1, PSoC 3, PSoC 4, and PSoC 5 programmable system-on-chip families. Cypress is the world leader in capacitive user interface solutions including CapSense® touch sensing, TrueTouch® touchscreens, and trackpad solutions for notebook PCs and peripherals. Cypress is the world leader in USB controllers, which enhance connectivity and performance in a wide range of consumer and industrial products. Cypress is also the world leader in SRAM and nonvolatile RAM memories. Cypress serves numerous major markets, including consumer, mobile handsets, computation, data communications, automotive, industrial, and military. Cypress trades on the NASDAQ Global Select Market under the ticker symbol CY. Visit Cypress online at www.cypress.com.


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