paul@8 | 1 | Introduction
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paul@8 | 2 | ------------
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paul@8 | 3 |
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paul@8 | 4 | The AcornElectronCartridge distribution provides schematic and circuit layout
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paul@8 | 5 | files for use with KiCad describing a breakout or prototyping cartridge
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paul@8 | 6 | suitable for use with the Acorn Electron microcomputer's Plus 1 expansion
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paul@8 | 7 | unit.
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paul@8 | 8 |
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paul@8 | 9 | The following resources are provided:
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paul@8 | 10 |
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paul@8 | 11 | AcornElectronCartridge.kicad_pcb The circuit board layout
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paul@8 | 12 |
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paul@8 | 13 | AcornElectronCartridge.net The netlist, generated from the schematic
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paul@8 | 14 | and distributed here for convenience
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paul@8 | 15 |
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paul@8 | 16 | AcornElectronCartridge.pro The KiCad project file
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paul@8 | 17 |
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paul@8 | 18 | AcornElectronCartridge.sch The circuit schematic providing the
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paul@8 | 19 | relationships between components
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paul@8 | 20 |
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paul@8 | 21 | AcornElectron.lib Acorn Electron component library
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paul@8 | 22 | containing definitions for the edge
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paul@8 | 23 | connector (used by the schematic editor)
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paul@8 | 24 |
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paul@8 | 25 | AcornElectron.pretty Acorn Electron component footprint library
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paul@8 | 26 | containing definitions of the edge
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paul@8 | 27 | connector (used by the PCB editor)
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paul@8 | 28 |
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paul@8 | 29 | BoardOutline Drawings defining the board outline plus
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paul@8 | 30 | descriptions of the drafting workflow and
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paul@8 | 31 | KiCad import considerations
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paul@8 | 32 |
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paul@8 | 33 | Overview
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paul@8 | 34 | --------
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paul@8 | 35 |
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paul@8 | 36 | The purpose of a cartridge breakout is to route the signals from the cartridge
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paul@8 | 37 | socket to "breakout" connectors that are easily accessed for prototyping
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paul@8 | 38 | purposes. The circuit board is plugged into the cartridge socket and the two
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paul@8 | 39 | sides of the board edge connector make contact with the socket contacts.
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paul@8 | 40 |
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paul@8 | 41 | Preparing the Schematic
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paul@8 | 42 | -----------------------
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paul@8 | 43 |
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paul@8 | 44 | Since the purpose of the board is merely that of routing signals, the
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paul@8 | 45 | schematic is very simple. Connectors corresponding to the two sides of the
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paul@8 | 46 | board edge connector are introduced, together with breakout connectors
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paul@8 | 47 | corresponding to the exposed signals. Each edge connector pin is labelled and
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paul@8 | 48 | a corresponding breakout connector pin is given a matching label. Thus, an
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paul@8 | 49 | association is established between the edge connector pin and the breakout
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paul@8 | 50 | pin.
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paul@8 | 51 |
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paul@8 | 52 | The CvPcb tool in KiCad associates components with footprints. For convenient
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paul@8 | 53 | prototyping, the breakout connectors are associated with headers with 0.1 inch
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paul@8 | 54 | pin spacing (or pitch). The edge connectors are associated with specially
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paul@8 | 55 | designed footprints for the Acorn Electron cartridge provided by the Acorn
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paul@8 | 56 | Electron footprint component library (AcornElectron.pretty).
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paul@8 | 57 |
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paul@8 | 58 | Preparing the Board Outline
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paul@8 | 59 | ---------------------------
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paul@8 | 60 |
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paul@8 | 61 | In order to produce a board of the right shape (or indeed of any shape), a
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paul@8 | 62 | board outline must first be produced. The BoardOutline directory contains
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paul@8 | 63 | documentation of the workflow involved in applying measurements used by other
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paul@8 | 64 | cartridges to produce a suitable drawing (cartridge_board_rear.dxf) which can
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paul@8 | 65 | then be used in KiCad (and by subsequent production tools) to establish the
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paul@8 | 66 | correct positions and dimensions of board features such as mounting holes and
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paul@8 | 67 | the edge connector portion of the board.
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paul@8 | 68 |
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paul@8 | 69 | This board outline is exported as DXF (using version 14 in Inkscape) and
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paul@8 | 70 | imported into KiCad to provide the basis of the board itself. The outline is
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paul@8 | 71 | imported into the Edge.Cuts layer, indicating that it shall be used to direct
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paul@8 | 72 | cutting tools to define the shape of the board. In order to align the outline
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paul@8 | 73 | with a grid using 0.127mm (0.05 inch) units, the origin of the outline is
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paul@8 | 74 | positioned at (60.445mm, 127mm). More information about the calculations can
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paul@8 | 75 | be found in the BoardOutline documentation.
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paul@8 | 76 |
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paul@8 | 77 | Preparing the Board Layout
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paul@8 | 78 | --------------------------
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paul@8 | 79 |
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paul@8 | 80 | Each component must be positioned appropriately on the board for it to make
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paul@8 | 81 | any physical sense. The edge connector footprints must be placed on each side
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paul@8 | 82 | of the protruding portion of the board, and the breakout connector footprints
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paul@8 | 83 | must be placed high enough up on the board to be accessible when the cartridge
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paul@8 | 84 | is inserted into the Plus 1. Beyond this, board layout is mostly a matter of
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paul@8 | 85 | routing tracks between connectors and avoiding board features such as mounting
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paul@8 | 86 | holes and the board edges.
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paul@8 | 87 |
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paul@8 | 88 | Design Rules and Production
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paul@8 | 89 | ---------------------------
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paul@8 | 90 |
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paul@8 | 91 | It was decided that OSHPark would be used to make the first set of boards.
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paul@8 | 92 | Thus, the design rules for OSHPark were added to the project configuration.
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paul@8 | 93 | Such rules can be found here:
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paul@8 | 94 |
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paul@8 | 95 | http://docs.oshpark.com/services/two-layer/
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paul@8 | 96 | http://docs.oshpark.com/design-tools/kicad/kicad-design-rules/
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paul@8 | 97 |
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paul@8 | 98 | The board uploaded to OSHPark was tagged with oshpark-648KdmKd in this
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paul@8 | 99 | repository. It resides on OSHPark at the following location:
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paul@8 | 100 |
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paul@8 | 101 | https://oshpark.com/shared_projects/648KdmKd
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paul@8 | 102 |
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paul@8 | 103 | Contact, Copyright and Licence Information
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paul@8 | 104 | ------------------------------------------
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paul@8 | 105 |
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paul@8 | 106 | The author can be contacted at the following e-mail address:
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paul@8 | 107 |
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paul@8 | 108 | paul@boddie.org.uk
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paul@8 | 109 |
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paul@8 | 110 | Copyright and licence information can be found in the docs directory - see
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paul@8 | 111 | docs/COPYING.txt and docs/gpl-3.0.txt for more information.
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