2020-08-08 15:47:34 +02:00
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<!DOCTYPE html>
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<html>
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<head>
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<title>XSCHEM ELEMENTS</title>
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<link rel="stylesheet" type="text/css" href="xschem_man.css" />
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/* Local styling goes here */
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p{padding: 15px 30px 10px;}
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</style>
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</head>
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<body>
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<!-- start of slide -->
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<div class="content">
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<!-- navigation buttons -->
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<a href="run_xschem.html" class="prev">PREV</a>
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<a href="xschem_man.html" class="home">UP</a>
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<a href="building_xschem_symbol.html" class="next">NEXT</a>
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<!-- slide title -->
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<h1> XSCHEM ELEMENTS</h1><br>
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<h3> WIRES </H3>
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<p>
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Wires in XSCHEM are the equivalent of copper traces in printed circuit boards or electrical conductors.
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Wires are drawn as lines but the electrical connectivity graph is built by XSCHEM.
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To draw a wire segment point the mouse somewhere in the drawing window and press the <kbd>'w'</kbd> key.
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A rubber wire is shown with one end following the mouse. Clicking the left mouse button
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finishes the placement. The following picture shows a set of connected wires. There are many
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wire segments but only 3 electrical nodes. XSCHEM recognizes connection of wires and uses this
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information to build up the circuit connectivity. All wires are drawn on the 'wire' layer. One
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electrical node in the picture below has been highlighted in red (this is a XSCHEM function we
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will cover later on).
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</p>
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<img src="xschem_wires.png">
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<h3> LINES </h3>
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<p>
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Lines are just segments that are used for drawing. Lines do not have any electrical meaning, in fact
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when building the circuit netlist, lines are completely ignored. XSCHEM uses different layers to draw
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lines. Each layer has its own color, allowing to draw with different colors. Lines are placed like
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wires, but using the <kbd>'l'</kbd> key. The 'Layers' menu allows to select various different layers (colors)
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for the line.
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</p>
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<img src="xschem_lines.png">
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<h3> RECTANGLES </h3>
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<p>
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Rectangles like Lines are drawable on multiple layers, and also do not carry any electrical information.
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A specific 'PIN' layer is used to make pins that are used to interconnect wires and components.
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Different fill styles (or no fill) can be defined for each layer. Rectangles are placed with the
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<kbd>'r'</kbd> bindkey
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</p>
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<img src="xschem_rectangles.png">
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<h3> POLYGONS </h3>
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<p>
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Polygons are paths that can be drawn on any layer. Placements begins with the <kbd>'ctrl-w'</kbd> key
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2020-09-09 00:21:40 +02:00
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and continues as long as the user clicks points on the drawing area. Placement ends when:</p>
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2020-08-08 15:47:34 +02:00
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<ul>
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<li> the last point is coincident to the first point.</li>
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<li> or by clicking the <kbd>right mouse button</kbd>, for an open polygon. </li>
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<li> or by hitting the <kbd>Return</kbd> key, for a closed polygon
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(this can be done also by clicking the last point coincident to the first polygon point).</li>
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</ul>
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2020-09-09 00:21:40 +02:00
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<p>
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A <kbd>fill=true</kbd> attribute may be given to have the shape filled with the layer fill style.
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2020-08-08 15:47:34 +02:00
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</p>
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<img src="xschem_polygons.png">
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<h3> CIRCLES / ARCS </h3>
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<p>
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Arcs may be placed by hitting the <kbd>Shift-C</kbd> key. First click the start point, then the end point.
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Moving the mouse will show the arc passing thru the 2 points and the mouse waypoint.
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Clicking will place the arc.
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Arcs may be modified after creation by selecting in stretch mode (<kbd> Ctrl-Button1-drag </kbd>) one of the arc ends
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or the arc center:<br>
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- (end point selected in stretch mode): by starting a move (<kbd>m</kbd>)
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operation and moving the mouse the arc sweep may be changed.<br>
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- (start point selected in stretch mode):by starting a move (<kbd>m</kbd>) operation and moving the mouse the start arc angle may be changed.<br>
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- (arch center selected in stretch mode): by starting a move (<kbd>m</kbd>) operation and moving the mouse the arc radius may be changed.<br>
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If a circle is needed then use the <kbd>Ctrl-Shift-C</kbd> key combination.
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<br>A <kbd>fill=true</kbd> attribute may be given to have the shape filled with the layer fill style.
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</p>
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<img src="xschem_elements_01.png">
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<h3> TEXT </h3>
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<p>
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Text can be placed with the <kbd>'t'</kbd> bindkey.
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A dialog box appears where the user inputs the text and text size.
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</p>
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<img src="xschem_texts.png">
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<p>
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The <kbd>layer</kbd> property can be used
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to draw text on a different layer, for example, setting <kbd>layer=6</kbd> will draw on cyan color.
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2020-08-25 02:10:15 +02:00
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A <kbd>font</kbd> property is defined to change the default font.
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A <kbd>hcenter=true</kbd> attribute may be set to center text in the reading direction,
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while <kbd>vcenter=true</kbd> centers text in the perpendicular (to reading) direction.
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the 2 attributes may be set both to get full centered text box.
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</p>
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<img src="xschem_elements_02.png">
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<p>
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You wil learn in the <a href="xschem_properties.html">xschem properties chapter</a>
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how to set, edit and change object properties.
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</p>
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<img src="xschem_texts1.png">
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<h3> SYMBOLS </h3>
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<p>
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Symbols are graphical elements that represent electrical components. A symbol represents an electronic
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device, like for example a resistor, a bipolar transistor, an amplifier etc. As you can see graphically
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symbols are built with lines, rectangles, polygons and texts, the graphical primitives shown before.
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In the picture below some components are placed in a schematic window. Components are instances of symbols.
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For example you see three placements of the 'npn' bipolar transistor symbol.
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Like in C++, where objects are instances of classes, here components are instances of symbols.
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</p>
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<img src="xschem_symbols.png">
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<p>
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Symbols (like schematic drawings) are stored in xschem libraries.
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For XSCHEM a library is just a directory placed under the
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XSCHEM_LIBRARY_PATH directory, see the <a href="install_xschem.html">installation slide</a>.
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A symbol is stored in a .sym file.
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</p>
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<pre class=code style="height: 240px;">
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user:~$ cd .../share/xschem/xschem_library/
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user:xschem_library$ ls
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devices
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user:xschem_library$ cd devices
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user:devices$ ls *.sym
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ammeter.sym generic.sym noconn.sym switch_hsp.sym
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arch_declarations.sym gnd.sym npn.sym switch.sym
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architecture.sym ind.sym opin.sym title.sym
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assign.sym iopin.sym package_not_shown.sym tline_hsp.sym
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attributes.sym ipin.sym package.sym use.sym
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bus_connect_not_shown.sym isource_arith.sym param_agauss.sym vccs.sym
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bus_connect.sym isource_pwl.sym param.sym vcr.sym
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capa.sym isource.sym parax_cap.sym vcvs.sym
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cccs.sym k.sym pmos3.sym vdd.sym
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ccvs.sym lab_pin.sym pmos4.sym verilog_delay.sym
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connect.sym lab_wire.sym pmosnat.sym verilog_timescale.sym
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delay_hsp.sym launcher.sym pnp.sym vsource_arith.sym
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delay_line.sym netlist_at_end.sym port_attributes.sym vsource_pwl.sym
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delay.sym netlist_not_shown.sym res.sym vsource.sym
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diode.sym netlist.sym spice_probe.sym zener.sym
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flash_cell.sym nmos3.sym spice_probe_vdiff.sym
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generic_pin.sym nmos4.sym switch_hsp_pwl.sym
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user:devices$ cd ...share/doc/xschem/
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user:xschem$ ls
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examples pcb
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</pre>
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<p>
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To place a symbol in the schematic window press the <kbd>'Insert'</kbd> key. A file chooser pops up,
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go to the xschem devices directory (<kbd>.../share/xschem/xschem_library/devices</kbd> in the distribution
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by default) and select a symbol (res.sym for example).
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The selected symbol will be instantiated as a component in the schematic at the mouse
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pointer coordinates.
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</p>
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<!-- end of slide -->
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<div class="filler"></div>
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</div>
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