DSPExplorer User`s Manual
Contents
1. far down on the feature list As stated above the playspace can have subdirectories There are two kinds of subdirectories A subdirectory which has the extension lib is taken to be a read only directory This is a good way to import a library of modules you don t want to modify A subdirectory which does not have a lib extension is take to be writable Of course if the files themselves are marked as read only by the host they cannot be written DSPExplorer keeps the file on the disk current Each time you make a modification to the design DSPExplorer will write the update to the file Thus there is no save command as things are always being saved The general goal of DSPExplorer is to allow you to stop what you are doing at any time and to return to that design at will WITHOUT remembering to save things If you close the window the goal is to have had everything already saved If you change schematics the schematic will already have been saved And so forth EXECUTION A quick note on execution When told to run DSPExplorer executes the source code of the modules The order of execution is dictated by the physical placement of the modules in the schematic Execution proceeds left to right It is the position of the upper left hand corner of the module which specifies position Signals between modules generally go left to right as well but this is NOT arequirement Feedback is possible These signal tr2. DSPExplorer User s Manual Introduction DSPExplorer is an Integrated Development Environment dedicated to learning about Digital Signal Processing It allows the user to write and run DSP software in a familiar highly interactive self contained environment As with many interactive working environments DSPExplorer is best described using videos However these videos can never convey all the details the user might wish to understand Further there are times when the user will want a short description of a feature without wading through lengthy videos Hence this document This document attempts to give a short description of each of the many features of DSPExplorer THIS DOCUMENT IS NOT A TUTORIAL It is assumed the reader knows how to navigate around the various screens and understands the basic workflow Organization of DSPExplorer There are really 6 screens e Schematic e Source e Scope e console e error e log Note that the console and error screens overlap and only one is visible at atime DSPExplorer attempts to bring the correct one to the front but you can change it by clicking on the appropriate label The log screen is essentially unused and probably should be removed There are three toolbars e Global Menu Bar Project Module Simulation Print e Module Menu Bar Single Abort file mod e Scope Menu Bar sigScale vScale SpecScale Menu items are specified using a path specifier such as Glob
3. aces look ugly Sorry They are rare enough I just didn t bother to make them pretty Module outputs are ALWAYS on the right and inputs are ALWAYS on the left There is no other way Again this sometimes make things a little ugly BUT there is never any ambiguity either Signal Selection In the scope area there are two times when you will want to select a signal to display the signal on the scope screen and to select a signal on which to trigger Signal selection is a cascading menu starting with the module name and followed by the upper level signals in the module Signals declared inside curly braces are NOT visible for triggering or display purposes Schematic Editing DSPExplorer s schematic editor is very simple Items are added using Module gt Add Things are deleted by moving them to the waste basket Each input of a module has a default wire The left end of the wire can be dragged to the output of any other module A wire can be selected by clicking on or very near any piece of the wire but it is always the left end that is moved never the right end Modules are moved around using click drag paradigm An unconnected input is assumed to be zero The schematic screen does not pan or zoom If you draw the schematic and then resize the window things may get lost There is no group selection only one thing is selected at a time Module Source Editing and Syntax The module source edit
4. al gt Open Schematic or Scope gt Trigger gt Window gt Blackman Some in the Scope section menu items can change their names based on their present value This can be confusing in this document but makes sense as you are operating DSPExplorer When this occurs the path will be given with braces showing the various possibilities Finally some menu options cannot be described in detail in this manual because their values depend on the design A prime example would be selecting a signal to display When this happens this document will use the lt gt braces to indicate that the selection is design dependent and an example is being shown FILE STRUCTURE DSPExplorer operates in a playspace which is a directory and all its subdirectories on the host file system Generally speaking files are created in that playspace or subdirectories of that playspace It is possible to include files from outside the playspace but those files will be read only To import a module from outside the playspace simply add it to the schematic and then Module gt Clone the module This will create a local module with the same contents Don t forget to delete the original kind of like Arnie s The Sixth Day Importing a schematic is problematic because DSPExplorer doesn t take note of where the schematic is when looking for the modules in the schematic This may get improved but improving this behavior is pretty
5. dule is added to the schematic and opened for examination modification in the source screen If the module is not from the working playspace it will be marked as read only Module gt Clone Copy the presently selected module into anew module You will be asked to provide a new name The module will be created in the working playspace Simulation gt Run Run the simulation if there are no errors Simulation gt Halt Halt the simulation at the end of the given left to right evaluation You can continue from this smoothly Simulation gt AutoRun Automatically start the simulation after a parameter has been changed Simulation gt Continue Continue a simulation after a Halt Simulation gt Single Run a single step complete left to right evaluation Simulation gt Abort Stop any running simulation Useful when you have an infinite loop in your code Unfortunately there is no indication of where the simulation was when the abort happened Room for enhancement Print gt Schematic Print the schematic Print gt Source Print the contents of the module being edited Print gt Scope Print the contents of the scope screen Source gt Single Run the module being edited ONCE This doesn t run the whole schematic just the module being edited Source gt Abort Abort any simulation running Good for infinite loops Source gt module mod This is really just a label of which module is being edited To edit a different module sel
6. e selected trace normally e Center display the selected trace usually a spectrum with 0 in the center rather than at the left e db display the 20log10 signal e Center db display the 20log10 signal centered usually for a spectrum Scope gt signal Specifies the signal presently selected Clicking on this allows one to add another signal Clicking on a signal label will change the value of this field The selected signal is displayed with a heavy line Scope gt Color Change the color of the selected signal
7. ect it using the schematic editor Scope gt sigScale Sets the horizontal scale of items displayed as signals Scope gt vScale Sets the vertical scale of whatever is selected for edit The item selected for edit is shown in bold on the trace screen and named in the signal part of the Scope toolbar Scope gt specScale Sets the horizontal scale of items displayed as spectra spectrums Spectra are scaled to fit entire on the screen when the specScale is 1 Scope gt Trigger gt signal The trigger menu item selects the operating mode for the Scope This includes e Scope gt Trigger gt signal Selects the trigger signal The value shown is the present value e Scope gt History value how many time samples are recorded for display The present value is shown This is the same number used to compute the spectrum when the signal is displayed as a spectrum Larger values will result in more precision e Scope gt Window value which windowing function will be used when computing the spectrum of signals The present value is shown none delivers the fewest surprises when looking at signals in the frequency domain Use of other windows can cause artifacts to appear on pure signals Be on guard e Scope gt Auto value how long should the simulation run before automatically triggering a display The present value is shown e Edge set the edge and AC DC coupling Use DC coupling whenever po
8. or is also quite simple Unlike the schematic editor the source editor does provide panning The editor is what is built in to java so it is primitive The most advanced feature is probably the ability to move an entire section of text from one place to another using cut and paste or select and drag I ve found it sufficient Syntax checking is performed continuously Error conditions are highlighted in red bold italics A hint as to why here is an error is shown in the error window at the bottom right of the screen Itisn ta very cleaver syntax machine but it gives reasonable hints The language used in DSPExplorer is very C like but there are important modifications First there are no functions each module is a self contained piece of code with well defined interfaces Inputs to the module may be signals from other modules compile time parameters or run time sliders Outputs may go to other modules As of version 3 2 there are three types of variables double which is a 64 bit IEEE754 floating point number fixed which is a fixed point number and complex which is to variables packaged together Variables may also be single dimension arrays Inputs and outputs may be arrays parameters and sliders may not Parameters and sliders are always double s Originally DSPExplorer had only doubles and complex numbers However several people asked where the integers and Booleans were To addres
9. ottom of the screen The value of the selected signal can be measured using the two sliders at the left hand side of the screen They are of the form gt where the indicates the vertical value of the selected signal Playing with these sliders is the easiest way to understand their use A quick note on Triggering DSPExplorer is a discrete time simulator which means even when the signals are displayed as lines as with a normal oscilloscope the signals are NOT continuous This complicates triggering somewhat To make the signals stable on the display it was necessary to interpolate the value of the trigger signal This is all well and good if you look at things using the Line display However when looking at things with a Bar display the Bar s seem to jitter left and right AND in magnitude This is simply the nature of the beast MENU ITEMS Project gt New Schematic Create a new schematic If you select an existing schematic you will asked if you want to override the existing schematic Project gt Open Schematic Open an existing schematic Project gt Save Schematic As Change the name of the working schematic and then save it under a new name Project gt Change Playspace Change the working playspace Module gt New Create anew module If you choose an existing module you will be asked if you want to override the existing Module gt Add Add an existing module to the schematic The mo
10. ro are printed as 0 for approximately 0 The precision changes release to release use sparingly To get a feel of the language and its use please watch a few of the videos or examine the source of one of the tutorial playspaces Scope Display Controls When the scope window is resized everything in it is resized as well All things considered this is probably wrong and may well be changed in the future The reason for this was to make sure things can t get lost when the window is sized downward Again this may change Signals can be added by clicking on the selected signal on the scope toolbar Signals are removed by moving them to the waste basket Signals are selected by clicking on their LABEL not by clicking on the actual line This may change Note that the trigger signal label is on the left hand side and all other labels are on the right The trigger signal cannot be discarded only replaced The scope can display two types of information spectra and time domain signals The spectra can be independently scaled and panned Panning takes play by moving the lt Spectra gt slider at the top of the window Time domain signals are panned using the lt Signals gt slider at the bottom of the screen The trigger level can be adjusted using the L gt slider on the left hand side of the screen The trigger position relative to the history buffer is moved by moving the lt T gt slider at the b
11. s these shortcomings DSPExplorer version 3 2 introduced fixed numbers By default a fixed number is a 32 bit signed integer Fixed and complex types of variables can have a precision modifier which immediately follows the type and specifies the number of bits including a sign bit before and after in the form b a For example many fixed point DSP processors have a 16 bit word which has a sign bit and 15 fractional number They can represent any number between 1 and almost 1 with 15 bits of precision DSP explorer would declare such a variable as fixed 1 15 example complex 1 15 twoFixeds Generally speaking one should always use a double whenever possible because this is the native data type in DSPExplorer NOTE fixed numbers are less efficient and doubles because DSPExplorer must verify the value of a fixed each time it is updated Booleans are implemented in the C way 0 is false and everything else is true The only reason for a Boolean is performance and as with integers it just isn t that much an improvement The language has a fair number of built in functions described elsewhere The println and print functions print out strings and variables Entire arrays can be printed using a single print statement Printing is assumed to be informative so variable precision is truncated to only a few decimal places Variables whose values are close to but not exactly ze
12. ssible The present value is shown Scope gt Real Imag Complex For the selected signal control what information is shown Real is just the real part Imag is the imaginary part Complex is both The Real part is always shown as a solid line the imaginary part is always dashed Scope gt Line Bar Line amp Bar For the selected signal display the signal as line s or as vertical Bar s or as both For the bar case if the horizontal scale is such that the bars would merge the line format is used instead regardless of this setting Scope gt Sig Ref asSpec FFT IFFT Mag PeakMag How to display the selected signal Sig display as a normal time domain oscilloscope trace Ref as a normal time domain trace This is usually used to display arrays such as filter kernels asSpec as aspectrum This is used to simply array asa spectrum rather than as a time domain signal FFT display the FFT of the selected signal Used to examine the spectrum of a signal IFFT display the Inverse FFT of the selected signal If displayed as Complex the real and imaginary parts are both shown e Mag display the spectrum MAGNITUDE of the selected signal If being displayed as Complex the imaginary part is the angle e PeakMag keep the peaks of the Magnitudes of the spectrum of the selected signal Useful when examining the passband of filters and the like Scope gt Normal Center db Centerdb e Normal display th
Download Pdf Manuals
Related Search