S.N.A.K.E.: A Dynamically Reconfigurable Artificial Sensate Skin ...

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Once the process is stopped, the file is closed, the thread is finished and all buttons are now enabled (except for the Stop Sampling button). The file is stored in a Microsoft Excel readable format so that further processing/plotting can be done. It is important to mention that although the application is capable of showing the data from any one of the sensor modalities in the Skin Patches, the functionality to extract data from all sensing modalities at once has not been implemented so far 12 because of the complexity involved in displaying data from many different sensing modalities effectively. Sampled data is also controlled by the installed application on the nodes, therefore if a different sensor needs to be sampled, the application on the nodes has to be changed. Data extracted from all types of sensors will be shown in the results chapter. 4.2.4 Other Functions Finally there were some other minor functions that were not mentioned before, but that are also useful to have. These are summarized in the following list: Resetting Brains (Button 12): useful if either the Brain or the I 2 C bus gets stuck Executing node applications (Button 10): to indicate the Bootloader to start execution Resetting nodes (Button 9): resets either a single node, or the entire patch. Amount of bytes received (component 15): useful to debug the network. Address validation (component 7): The node address must be in the valid range (0-1023) or the task buttons will not be enabled Many other functions of the software were left unmentioned intentionally, however the reader is welcome to check the full listing of the different project files in Appendix E. 12 This means for example that temperature readings and light readings can’t be sampled at once, but not that several nodes can’t be sampled at the same time which as it was previously noted is indeed possible 100
4.3 Communications Software The last part of the software section corresponds to the specifics of the communications channels used in the entire project. This will briefly outline some of the necessary design choices that were taken along the whole process. 4.3.1 I2C Backbone We have talked about the hardware considerations of the I 2 C backbone, but nothing has been mentioned about the software that runs the bus. The I 2 C bus requires two lines to be routed among all devices which are to be connected to it plus a common ground. This means that whenever a device needs to talk to another one in the bus, it needs a way to address it. In fact the I 2 C bus has two different addressing schemes: 7-bit and 10-bit. The addressing scheme is actually the theoretical limit to the number of devices that can coexist in the same bus. The first one allows a maximum of 2 7 − 1 = 128 devices while the second one allows 2 10 − 1 = 1023 devices. Naturally, the second one was chosen to allow a larger number of devices to be connected to the bus. These numbers are not the actual allowed limit, because the input capacitance of all pins connected to the bus add to the total, which as we already mentioned cannot exceed 400 pico-farads. We already mentioned some ways to get around this limitation, however for the case of the current project, the real limit to this will be presented in the Results Chapter. There are however several questions that must be answered though: How are these addresses assigned? Is it the Bootloader which assigns the address or is it the application code or both? What happens if there are more than one device in a Skin Patch with the same address? How is the bus arbitrated? First of all, the scope of an I 2 C address is limited to the Patch of Skin to which the node is connected. So although there can’t be two nodes with the same address in the same Patch of Skin, addresses can be reused if a different Brain is used. In other words, as long as there are not two nodes with the same address on the same Skin Patch, addresses can be 101
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Author S.N.A.K.E.: A Dynamically Re
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S.N.A.K.E.: A Dynamically Reconfigu
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Table of Contents Abstract 3 Acknow
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List of Figures 2-1 Created by MIT
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E-1 OpenGL Control Header File . .
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Chapter 1 Introduction “Imaginati
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The current project, named S.N.A.K.
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Hardware Each Skin Patch is compose
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living tissue. Particularly in the
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Figure 2-2: Leonardo’s Hand great
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Artificial Sensate Skins elsewhere
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2.1.2 Ultra-dense Sensor Arrays Thi
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2.2 Flexible Circuits Although, not
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2.2.2 Other Technologies Figure 2-6
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human skin. The following design pr
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(a) Skin Patches as data extraction
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Figure 3-3: I 2 C Routing pattern T
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3.2.2 Peer to Peer As we already me
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5. Audio: by adding a MEMS micropho
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Table 3.1: Material thicknesses and
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(a) Node Front (b) Node Back Figure
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Page 52 and 53: used, which only further complicate
Page 54 and 55: 8. Teardrops and filleting were add
Page 56 and 57: (a) 7.4V, 2.2mAh Li-ion Battery (b)
Page 58 and 59: in more detail in the Results Chapt
Page 60 and 61: has a 30mA forward current with a f
Page 62 and 63: Figure 3-14: Strain gage layer prot
Page 64 and 65: an unbalanced Wheatstone bridge, fr
Page 66 and 67: Figure 3-16: QTC response curve for
Page 68 and 69: (a) Prototype boards used to calibr
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Page 72 and 73: Sound The only sensing modality add
Page 74 and 75: Figure 3-20: Brain regular PCB fabr
Page 76 and 77: 3.4.3 Communications unit The Commu
Page 79 and 80: Chapter 4 Software “A Scientist d
Page 81 and 82: Networks. Why is this relevant? Mai
Page 83 and 84: Figure 4-1: Bootloader memory map C
Page 85 and 86: Bit Flag Name Description 0x01 FILE
Page 87 and 88: Figure 4-3: Sampling timing example
Page 89 and 90: We also mentioned before that there
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Page 93 and 94: Component Description 1 Indicates t
Page 95 and 96: last chapter. Figure 4-5: Automatic
Page 97 and 98: An important point to stress is tha
Page 99: (a) Rotation control (b) Zooming co
Page 103 and 104: 4.3.2 Peer to Peer Peer to peer com
Page 105 and 106: Chapter 5 Analysis of Results and E
Page 107 and 108: Figure 5-1: Stress concentration po
Page 109 and 110: of the assembled skin patch don’t
Page 111 and 112: Node SG1 SG2 R(X) R(Y) Δ(X) Δ(Y)
Page 113 and 114: Or, ∆R = R3 R3 R3 + RC (5.2) Howe
Page 115 and 116: R3 Microstrain 162Ω −99.7337969
Page 117 and 118: Figure 5-3: Strain Gage electronic
Page 119 and 120: (a) Data from both strain gages (b)
Page 121 and 122: (a) Pressure data being extracted f
Page 123 and 124: many of these did not work as expec
Page 125 and 126: Data plots were also extracted for
Page 127 and 128: (a) Temperature sensor data plots (
Page 129 and 130: Figure 5-12: Raw microphone data wi
Page 131 and 132: (a) Activity sensor data (b) Whiske
Page 133 and 134: 5.3 Performance Metrics We have pre
Page 135 and 136: (a) I 2 C data when a 1500Ωs resi
Page 137 and 138: Component # per node Current consum
Page 139 and 140: Finally, since power is readily ava
Page 141 and 142: Chapter 6 Conclusions and Future Wo
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Page 145 and 146: Implement P2P Communications: curre
Page 147 and 148: Appendix A Abbreviations and Symbol
Page 149 and 150: Appendix B Bill of Materials 149
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Appendix C Schematics and PCB Layou
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1 1 2 2 3 3 4 4 D D C C B B A A Tit
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Amp1 P0Amp101 P0Amp102 P0Amp103 P0A
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P0Cin02 P0East06 P0North06 P0South0
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Cain P0C ain01 P0Cain02 L1 P0L101 P
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Figure C-10: Node Bottom Overlay 16
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4 3 2 1 A A Brain Communications Ac
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C3v P0C3v01 P0C3v02 Cavcc P0Cavcc01
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Appendix D Firmware 167
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C:\Documents and Settings\Gerardo\M
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Appendix E PC Code 183
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1 c:\Documents and Settings\Gerardo
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12 c:\Documents and Settings\Gerard
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Bibliography [1] John C. Ansel. Ski
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[33] Joseph Jacobson, B Comiskey, C
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[68] Vilis Tutis. The physiology of
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