149 lines
8.8 KiB
HTML
149 lines
8.8 KiB
HTML
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<!DOCTYPE html>
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<html>
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<head>
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<title>GRAPHS</title>
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<link rel="stylesheet" type="text/css" href="xschem_man.css" />
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<style type="text/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="simulation.html" class="prev">PREV</a>
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<a href="xschem_man.html" class="home">UP</a>
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<a href="developer_info.html" class="next">NEXT</a>
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<!-- slide title -->
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<h1>VIEWING SIMULATION DATA WITH XSCHEM</h1><br>
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<p>
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Usually when a spice simulation is done you want to see the results, this is usually accomplished
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with a waveform viewer. There are few open source viewers, like
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<a href="https://github.com/StefanSchippers/xschem-gaw">GAW</a>... <br>
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<img src="graphs02.png"><br>
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...Or ngspice internal plotting facilities:<br>
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<img src="graphs01.png"><br>
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There is also an interesting commercial product from Analog Flavor, called
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<a href="https://www.analogflavor.com/en/bespice/">BeSpice (bspwave)</a>
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that offers a free of charge one year evaluation license for non commercial use:<br>
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<img src="graphs03.png"><br>
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All these waveform viewers are supported by xschem and more can be added, just by giving the command line
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to start the viewer to xschem in the <kbd>Simulation-> Configure simulators and tools</kbd> dialog:<br>
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<img src="graphs04.png"><br>
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For <a href="">gaw</a>
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and
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<a href="file:///home/schippes/mysite/stefan/xschem_man/video_tutorials/probe_to_bespice.mp4">bespice</a>
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xschem can automatically send nets to the viewer by clicking a net on the schematic
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and pressing the <kbd>Alt-G</kbd> key bind or by menu <kbd>Hilight->Send selected nets/pins to Viewer</kbd>
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<br>
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<img src="graphs05.png"><br>
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</p>
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<h2>Using XSCHEM's internal graph functions</h2>
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<p>
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Xschem can now display waveforms by itself in the drawing area. in the Simulation menu there is an entry to
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add a graph: <kbd>Add waveform graph</kbd>. When this menu is pressed a box can be placed in the schematic:<br>
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<img src="graphs06.png"><br>
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The next step is loading the simulation data, This is done by menu
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<kbd>Simulation->Load/Unload ngspice .raw file</kbd>. This command loads a .raw file produced by a ngspice/Xyce
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simulation. The file name is expected to be <kbd>circuit.raw</kbd> where
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<kbd>circuit.sch</kbd> is the name of the schematic opened
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in the drawing area. The raw file is searched for in the simulation/netlisting directory
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<kbd>Simulation ->set netlist dir</kbd>.<br>
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After placing a graph box and loading simulation data a wave can be added. If you place the mouse on the inside
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of the box, close to the bottom/left/right edges and click the graph will be selected.
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You can also select a graph by dragging a selection rectangle all around it.
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This tells xschem where
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new nodes to be plotted will go, in case you have multiple graphs.
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Then, select a node or a net label, press 'Alt-G', the net will be added to the graph. Here after a
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list of commands you can perform in a graph to modify the viewport. These commands are active when
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the mouse is Inside the graph (you will notice the mouse pointer changing from an arrow to a <kbd>+</kbd>).
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if the mouse is outside the graph the usual Xschem functions will be available to operate on schematics:
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</p>
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<ul>
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<li>Pressing <kbd>f</kbd> with the mouse in the middle of the graph area will do a full X-axis zoom.</li>
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<li>Pressing <kbd>f</kbd> with the mouse on the left of the Y axis will do a full Y-axis zoom.</li>
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<li>Pressing <kbd>Left/Right</kbd> or <kbd>Up/Down</kbd> arrow keys while the mouse is inside a graph will
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move the waveforms to the left/right or zoom in/zoom out respectively.</li>
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<li>Pressing <kbd>Left/Right</kbd> or <kbd>Up/Down</kbd> arrow keys while the mouse is on the left of the Y-axis
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will move the waveforms or zoom in/zoom out in the Y direction respectively.</li>
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<li>Pressing the <kbd>left</kbd> mouse button while the pointer is in the center of the graph
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will move the waves left or right following the pointer X movement.</li>
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<li>Pressing the <kbd>left</kbd> mouse button while the pointer is on the left of the Y-axis
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will move the waves high or low following the pointer Y movement.</li>
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<li> Doing the above with the <kbd>Shift</kbd> key pressed will zoom in/out instead of moving.</li>
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<li> pressing <kbd>a</kbd> and/or <kbd>b</kbd> will show a vertical cursor.
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The sweep variable difference between the <kbd>a</kbd> and the <kbd>b</kbd> cursor is shown and
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the values of all signals at the X position of the <kbd>a</kbd> cursor is shown. </li>
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<li> Double clicking the <kbd>left</kbd> mouse button with the pointer above a wave label will
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allow to change its color.</li>
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<li> Pressing the <kbd>right</kbd> mouse button with the pointer above a wave label will show it in bold.</li>
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<li> Double clicking the <kbd>left</kbd> mouse button with the pointer in the middle of the graph will show a
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configuration dialog box, where you can change many graph parameters.</li>
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<li> Pressing the <kbd>right</kbd> mouse button in the graph area and dragging some distance in the X direction
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will zoom in the waveforms to that X range.</li>
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</ul>
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<p>
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<img src="graphs07.png"><br>
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The graph configuration dialog box which is shown by <kbd>left</kbd> button double clicking inside the graph,
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allows to change many graph attributes, like number of X/Y labels, minor ticks, wave colors, add waves
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from the list of waves found in the raw file, select the dataset to show in case of multiple sweep simulations
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and more.<br>
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<img src="graphs08.png"><br>
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The text area with the colored wave names is just a text widget. You can manually edit it to add / remove waves,
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or you can place the cursor somewhere in the text, select some waves from the listbox on the left, press the
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<kbd>Add</kbd> button to have these waves added.
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If you place the insertion cursor in the middle of a node name in the text area, you can click the color
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radio buttons on the bottom to change the color. The <kbd>Search</kbd> entry can be used to restrict the list
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of nodes displayed in the listbox. The Search entry supports regular expression patterns. For example,
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<kbd>^X</kbd> will match all nodes that begin with <kbd>X</kbd>, <kbd>xm[0-9]\.</kbd> will match all nodes
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containing xm followed by one digit and a dot.
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</p>
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<h3>Display bus signals</h3>
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<p>
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If you have a design where digital signals are present you might want to group some of these to form a
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bus and display these bundled signals.
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After placing a graph box and loading the simulation data as explained above, left-double click the graph
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to show the configuration dialog, check the <kbd>bus</kbd> and <kbd>digital</kbd> check boxes,
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use the <kbd>Search</kbd> text entry to restrict the list of signals,
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then select all the signals you want to show as a bus and click the <kbd>Add</kbd> button. Also set the
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<kbd>Min value</kbd> and the <kbd>Max value</kbd> of the signals in the bus. This information is needed
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by Xschem to calculate the logic high and logic low thresholds. Currently the logic '1' is set at 80%
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of the signal min-max range and the logic '0' level is set at 20% of the signal range.
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After pressing the <kbd>Add</kbd> button a bus is shown in the text area. The first field is a template
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<kbd>BUS_NAME</kbd> you should change to give a meaningful name to the bus.<br>
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<img src="graphs09.png"><br>
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You will then see your bussed signal in the graph:<br>
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<img src="graphs10.png"><br>
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If you have bussed signals in the schematic , like <kbd>LDA[12:0]</kbd> and your graph has the
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<kbd>Digital</kbd> and <kbd>Bus</kbd> checkboxes set you can simply add the LDA bus to the graph by
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clicking the net in the schematic (with the configuration dialog open) and pressing <kbd>Alt-G</kbd>:<br>
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<img src="graphs11.png"><br>
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You can add many signals to see them stacked in a very compact view:<br>
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<img src="graphs12.png"><br>
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It is possible to switch the graph to analog mode, by unchecking the <kbd>Digital</kbd> checkbox in the graph
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configuration dialog, to better see the waveforms. Switching back to Digital yields the previous view.
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In analog mode buses are not shown, but are not lost. You will see them again when switching back to
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Digital mode. <br>
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<img src="graphs13.png"><br>
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Many graphs can be created in a schematic, and the configuration of all graphs (viewport, list of signals,
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colors) is saved together with the schematic. If you re-run a simulation just unloading/loading the data from
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the simulation menu will update the waveforms.<br>
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<img src="graphs14.png"><br>
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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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<!-- frame footer -->
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<iframe seamless src="xschem_footer.html" class="footer_iframe" >
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</body>
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</html>
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