Design and Application of a Contact Barcode Reader, for Use on Low-Visibility Printed Conductive Patterns
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Brunel University School of Engineering and Design Julian Wood Design and application of a contact barcode reader, for use on low-visibility printed conductive patterns MPhil Thesis Brunel University School of Engineering and Design MPhil Thesis Academic Year 2007 - 2008 Julian Wood Design and application of a contact barcode reader, for use on low-visibility printed conductive patterns Supervisors: Prof. D. Harrison, Dr D. Southee December 2008 This thesis is submitted in partial fulfilment of the requirements for a degree of Masters of Philosophy Abstract This thesis presents the design and development of a hand-held electronic reader, designed to decode conductive patterns printed on a paper substrate. Data read from the patterns, by the reader, is used to trigger events in the digital domain. The reader and associated conductive patterns are devices for linking paper documents with the digital world. The patterns are formed by masking conductive-coated paper with a non-conductive, printed lacquer. The reader is a low cost and ergonomic device, capable of transmitting the embedded data from the conductive paper to the computer. The first reader designed and developed was tethered to a computer by data cable, using the USB communication protocol. The second design was developed further, with transmission of data achieved by replacing the cable with short-range Bluetooth wireless technology. Both devices were designed and developed using embedded systems and low cost electronic components. Additional work was undertaken to optimise the device's mechanical structure, ergonomics and integration of hardware. Alongside the development of the reader, test and development work was carried out to optimise the printed media, in materials and design. User trials demonstrated that the complete printed and reading system was functional, with varied rates of success among participants. Further work is required to improve the conductivity of the coated paper, and the accuracy of the decoding algorithm. II Acknowledgements Our gratitude goes to the EU FP6 for funding the research project and to all of our partners: King’s College London, Acreo AB, Anoto AB, ArjoWiggins SAS, ETH Zurich, Malmö University, Pearson Education and Edexcel, and all the participants of the user studies who volunteered their time. III Table of Contents Abstract ........................................................................................................................... II Acknowledgements ........................................................................................................III Chapter 1: Introduction................................................................................................. 10 1.1 Objectives of the research................................................................................. 10 1.2 Background........................................................................................................ 11 1.3 Overview of the design of the new Brunel tethered barcode reader............. 13 1.4 Thesis Structure................................................................................................. 15 Chapter 2: Literature review ......................................................................................... 16 2.1 The persistence of paper ................................................................................... 16 2.1.1 Linking devices and hardware solutions: wands, barcode readers, pens, tablets, and cameras................................................................................................ 17 2.1.2 Barcode history and symbology ................................................................... 17 2.1.3 Integrated systems utilising barcodes and other patterns ....................... 20 2.1.4 Anoto pen and related technologies ............................................................. 23 2.1.5 Paper++ and SuperInks................................................................................. 25 2.1.6 Similar contact technologies......................................................................... 27 2.1.7 Natural History Museum trial of augmented paper...................................... 27 2.2 Summary .......................................................................................................... 28 Chapter 3: Mechanical and ergonomic design of the reader ...................................... 29 3.1 The Conductive Tip...................................................................................... 29 3.1.1 Previous work in this area ............................................................................ 29 3.1.2 Investigation into electrical and physical robustness of tip configurations.. 29 3.1.3 Evaluation of the parallel tip design............................................................. 30 3.1.4 Design of concentric tips.............................................................................. 30 3.1.5 Evaluation of the concentric tip design ........................................................ 31 3.1.6 Fully floating concentric tip design............................................................ 34 3.1.7 Evaluation of the fully floating concentric tip design ................................... 35 4 3.2 Synthesis of tip designs: the cantilever tip ...................................................... 35 3.3 Discussion on influence of tip configuration .................................................... 36 3.4 Appraisal of lacquer masks and conductive substrate.................................... 37 3.5 Ergonomic design of reader casings ................................................................ 39 3.6 First integrated reader design .......................................................................... 41 3.6.1 Evaluation of first integrated reader design................................................... 42 3.7 Second integrated reader design ...................................................................... 42 3.7.1 Evaluation of the second integrated reader design ........................................ 42 3.8 Final casing design for reader .......................................................................... 44 3.8.1 Evaluation of final reader casing design........................................................ 45 Chapter 4: Electronics: signal amplification and processing..................................... 46 4.1 Signal filtering.................................................................................................... 47 4.2 The microcontroller........................................................................................... 50 4.3 Wireless communications, and hardware integration ................................... 51 4.3.1 Selection of wireless protocols and electronics design ................................ 52 4.3.2 Further development of the wireless hardware............................................. 54 4.4 Power supply and management ....................................................................... 55 4.4.1 Power management using Sleep mode ......................................................... 56 4.4.2 Battery selection ........................................................................................... 59 4.4.3 Integrated wireless power management ....................................................... 62 Chapter 5: Software and firmware development......................................................... 64 5.1 Introduction ....................................................................................................... 64 5.2 Software interface.............................................................................................. 64 5.3 Microcontroller firmware................................................................................. 66 5.3.1 Initialising the microcontroller ..................................................................... 67 5.3.2 Basic swipe reading and decoding structure................................................. 67 5.3.3 Removing noise-derived data values............................................................ 67 5.3.4 “Glitch” procedure.................................................................................. 68 5 5.4 Introducing the barcode pattern...................................................................... 72 5.4.1 Decoding the barcode pattern....................................................................... 73 5.4.2 Adjustment of the data set ............................................................................ 73 5.4.3 Deducing the pattern in the data set.............................................................. 74 5.4.4 Decoding the pattern..................................................................................... 76 Chapter 6: Digital Pencil.............................................................................................. 78 6.1 The alternative nib concept .............................................................................. 78 6.1.1 Introduction .................................................................................................. 78 6.1.2 Prototypes and test method........................................................................... 79 6.1.3 Results .......................................................................................................... 80 6.1.4 Conclusions .................................................................................................. 81 6.2 'Digital'