HyungWon Kim

Efficient Multi-Touch Detection Algorithm for Large Touch Screen Panels

Large mutual capacitance touch screen panels (TSP) are susceptible to display and ambient noise. This paper presents a multi-touch detection algorithm using an efficient noise compensation technique for large mutual capacitance TSPs. The sources of noise are presented and analyzed. The algorithm includes the steps to overcome each source of noise. The algorithm begins with a calibration technique to overcome the TSP mutual capacitance variation. The algorithm also overcomes the shadow effect of a hand close to TSP and mutual capacitance variation by dynamic threshold calculations. Time and space filters are also used to filter out ambient noise. The experimental results were used to determine the system parameters to achieve the best performance.

Low power routing and channel allocation method of wireless video sensor networks for Internet of Things (IoT)

We propose a new method of multichannel allocation and routing for wireless mesh networks where each node generates event-driven video sensor data. Battery powered video camera sensors are often connected wirelessly to cover a large area. Such wireless video sensor networks are considered as major applications of Internet of Things (IoT). We analyze the power consumption model for wireless video sensor network. We then propose an algorithm to route the sensor nodes and allocate channels in a way that minimizes the overall power consumption while satisfying the required data transmission. We developed a wireless video sensor network simulator to prove the performance advantage of the proposed algorithm. Simulation results are provided with wireless sensor networks of various sizes.

Efficient algorithm for accurate touch detection of large touch screen panels

Large mutual capacitance touch screen panels (TSP) are susceptible to display and ambient noise. This paper presents a multi-touch detection algorithm using an efficient noise compensation technique for large mutual capacitance TSPs. The algorithm starts with a calibration technique to overcome TSP mutual capacitance variation. It also overcomes the shadow effect of a hand close to TSP and mutual capacitance variation by applying dynamic threshold calculations. Time and space filters are also used to filter out noise. Experimental results are used to determine system parameters for best performance.

Concurrent Driving Method with Fast Scan Rate for Large Mutual Capacitance Touch Screens

A novel touch screen control technique is introduced, which scans each frame in two steps of concurrent multichannel driving and differential sensing. The proposed technique substantially increases the scan rate and reduces the ambient noise effectively. It is also extended to a multichip architecture to support excessively large touch screens with great scan rate improvement. The proposed method has been implemented using 0.18 μm CMOS TowerJazz process and tested with FPGA and AFE board connecting a 23-inch touch screen. Experimental results show a scan rate improvement of up to 23.8 times and an SNR improvement of 24.6 dB over the conventional method.

Voltage shifting double integration circuit for high sensing resolution of large capacitive touch screen panels

We propose a new touch screen sensing circuit based on voltage shifting double integration scheme for large touch screen panels. The proposed circuit increases the sensing resolution by shifting integrated signal, while reducing the detection time by integrating both edges of sense signals. We implemented the proposed technique in FPGA and analog circuit with touch detection software. Experiments show that the proposed circuit improves both the touch performance and frame rate - key requirements for large touch screen controllers.

Ultra-low power OTA based on bias recycling and subthreshold operation with phase margin enhancement

An ultra-low power and wide bandwidth operational transconductance amplifier (OTA) is presented. The proposed OTA employs a folded cascode (FC) structure with an enhanced current recycling technique. It provides the advantages of rail-to-rail input and output swing, while presenting lower power consumption and higher DC gain than conventional FC. It substantially reduces the power consumption by operating all devices under subthreshold region. In addition, it improves the phase margin of the OTA via special property of all-subthreshold operation substantially enhanced recycling effect of RFC OTA that ensures high gain and bandwidth. We implemented the proposed OTA in a 65nm CMOS process technology. The post layout simulation results demonstrate a robust performance exhibiting a DC-gain of 50.7dB, and a unity gain bandwidth of 2.1KHz 27.3MHz for a capacitive load of 0.5pF15nF. It also provides high phase margin (PM) up to 90.5 with extremely low power consumption of 3.9W under a low supply voltage of 0.5V.

Design of a Frequency Division Concurrent sine wave generator for an efficient touch screen controller SoC

This paper presents an interleaved sine wave generator using an efficient memory access technique for large touch screen controllers. It concurrently applies sine waves of different frequencies. The proposed circuit improves the speed of touch detection and reduces the chip area compared with conventional analog oscillators. The range of sine wave frequencies and the gap between each of frequencies can be configured by adjusting the address calculation algorithm to fetch samples values stored in memory. Therefore it provides higher flexibility with configurable sine wave frequencies than conventional schemes. It also minimizes the memory size required to regenerate all the sine waves needed. The proposed architecture has been implemented the proposed sine wave generator in a touch screen controller with FPGA and analog front end board.

Distributed architecture of touch screen controller SoC for large touch screen panels

Currently large touch screen panels (TSP) tend to use projected capacitance technology, which allow multi touch and high sensitivity. For large TSPs with a large number of TX (driving) and RX (sensing) lines, however, it is increasingly challenging to achieve high sensitivity, high detection rate, and multi-touch. In this Paper, we propose a distributed architecture of touch screen controller where multiple controller SoCs collaborate in driving and sensing each section of a large TSP. We show that the proposed architecture and SoC design can increase the detection rate without loss of sensitivity performance. It also allows a smaller SoC implementation, while its chip expandability provides the flexibility of supporting a large range of TSP sizes. We implemented the proposed distributed SoC using TSMC CMOS 0.18um with a low power ARM core, AHB-lite bus, memories, and embedded touch algorithm software.

Utilization-Aware Channel Allocation and Routing for Mesh Networks for Battery-Powered Surveillance Cameras

Battery powered video camera sensors are often connected wirelessly to cover a large area. We propose a multi-channel allocation and routing method for wireless mesh networks where each node generates event-driven video sensor data. How the routing and channel allocation is done has large impact on the battery life time of such networks. We realistically analyze the power consumption model based on the utilization of each link. We then present an optimization formula of utilization-aware channel allocation and routing that minimizes the overall power consumption while transferring all the required video data. We developed an efficient heuristic algorithm that accurately approximates the formula. A network simulator has been developed, which show that the proposed method can reduce the overall power consumption.

New FFT design with enhanced scan rate for frequency division concurrent sensing of mutual-capacitance touch screens

As the touch screens become larger and demand higher resolution, various concurrent sensing methods have been developed for higher scanning speed and performance. One of such fast detection methods called the frequency division concurrent sensing (FDCS) employs an FFT to distinguish concurrent driving sine waves of different frequencies. In this paper, we propose a new FFT architecture and design, which can further improve the speed of the FDCS based controller for large mutual capacitance touch screens. The proposed FFT is used to increase the frame scan rate without duplicating sensing circuit. It uses only half the cycle of the driving signals to reconstruct the complete cycle of the signals, and so it can convert the signals to the complete frequency domain data. This paper shows that the proposed FFT architecture can double the frame scan rate with negligible loss in signal to noise ratio (SNR) and small area overhead.