WGM-201 Waveform Generator Manual
Contents
1. 7 3 Waveform Editor John Foster has developed the Wavemaker program to allow editing of a generator waveform using a graphical user interface Wavemaker is started from the Tools menu The Wavemaker manual is available from the Help manual 8 Synchronizing Two Generators Two or more generators my be synchronized On their rear panel connectors the waveform trigger out pin of generator 1 the master is connected to the waveform trigger in pin of generator 2 the slave Tek J M s M S 5 s f f f f f f F E Hi 5 00 M 500 u 5 Hi 5 00 TDS 2022 10 08 21 AM 5 6 2010 TDS 2022 10 05 31 AM 5 6 2010 a Waveforms b Expaned View Figure 11 Synchronized Waveforms 14 The slave generator must be set to a very slightly higher frequency than the master so that each waveform cycle completes before there is a new trigger signal Figure 11 shows the master waveform producing a 400Hz square wave The slave is producing a 400Hz sine wave The expanded view shows a flat spot on the slave waveform where it is waiting for the next trigger signal 9 Commands In this section we document commands that may be issued directly to the hardware The terminal emulator or programming language that sends these commands appears to do so using a a serial port connection to the hardware It is not necessary to deal with USB in any form Consequently any language that can send and receive commands via a serial port can communi2. Waveform Output a Enabled 28 ed Gisablec E a 0 315 60 Frequency Sweep i 70 Gisablec 10 80 C Enabled 7 90 Sweep Settings 1 100 gt 0 1 Figure 2 Minimum User Interface 2 1 Manual sweep e Click on the upper frequency limit at the top of the frequency slider and enter the maximum frequency of the sweep in Hertz eg 20000 e Click on the lower frequency limit at the bottom of the frequency slider and enter the minimum frequency of the sweep in Hertz eg 20 e Now drag the frequency slider between the bottom and the top limits The frequency will sweep between 20Hz and 20kHz as the slider is moved The characteristic Frequency Control Mode of the frequency slider can be switched to Logarithmic or Linear In linear mode the frequencies between maximum and minimum are spread evenly over the range of the slider In the default state this means that 3MHz is at the top of the slider 1 5MHz at the mid point and 300kHz at 10 from the bottom The bottom end of the scale is very compressed In logarithmic mode the frequencies are distributed like the keys on a piano This is a more natural arrange ment for human hearing and means for example that each decade frequency f to frequency 10f occupies the same linear space on the slider Consequently it s much easier to use to set a given frequency Logarithmic sweep mode has another advantage Many response curves have linear segments when the ampli t
3. 3 208 162 31 You can verify that this is correct Use View Debug Console to enable the console which shows messages being set to the hardware Click on the frequency readout enter the frequency value 2000000 into the New Frequency widget You will see the message F 3 208 162 31 sent to the hardware CN Select trigger mode where n is one of the following 0 Waveform Generator FreeaARRunning Mode 1 Waveform Generator Triggered Mode 2 Pattern Generator FreeaARRunning Mode 3 Pattern Generator Triggered Mode X Select trigger source 0 External Trigger 1 Manual Trigger 2 Counter Trigger rn PulseGenerator Mn n Yab Set trigger count command Parameters a and b make up a 16 bit number which dictates how many waveform or pat tern generator cycles are executed in triggered mode It uses an count up counter which overflows at 65536 so you program it with 65536 minus the number of cycles you want it to output after the trigger Using Y O 1 would output 65536 1 65535 cycles of the waveform after a trigger T Manual trigger 1 Pulse Generator Pen pulse generator duty cycle command Parameter c is the channel number Valid values are 1 and 2 Parameter n is an eight bit duty cycle value 0 is off 255 is fully on Gcabcd pulse generator frequency Parameter c is the channel number Valid values are 1 and 2 Parameters a b c d make up frequency integer see frequency command Enable pulse generator 1 Ou
4. Command Parameter c is the channel number either 1 or 2 Parameter n is an eight bit duty cycle value Duty Cycle 255 n 255 x 100 PWM Frequency Parameter e is the channel number either 1 or 2 Parameters a b c q specify the frequency See Frequency command and example below Enable PWM 1 output Disable PWM 1 output Enable PWM 2 output Disable PWM 2 output 17 Pattern Generator Com Enable Pattern Generator Output Set Pattern Generator Frequency frequency of the repetition rate of the sequence Set Pattern generator sample the command is lower case ell Pattern Generator Length The parameter n specifies the pattern length as follows 0 1024 samples 512 samples 256 samples 128 samples 64 samples 32 samples 16 samples 8 samples 4 samples 2 samples 1 2 3 4 5 6 7 8 9 Counter Commands Counter Mode Normal Counter Accumulator Frequency Counter Period 1 64 sec Frequency Counter Period 1 32 sec Frequency Counter Period 1 16 sec Frequency Counter Period 1 8 sec Frequency Counter Period 1 4 sec Frequency Counter Period 1 2 sec Frequency Counter Period 1 sec Frequency Counter Period 2 sec Counter Trigger Voltage Level where nn as an 8 bit ASCII value representing the trigger threshold voltage Trigger Level nn 127 127 x 10 volts Read Counter Returns 4 bytes corresponding to the 32 bit counter value high
5. Waveform Generator ar ie pem Output Mode 34 0 Polarity E Coni ons 31 oe A s E0 Pesitive Risna le Tore Burst 35 7 0 c er ss esate trea Pattern Generator 79 U Trigger Level Trigger Mode 16 5 9 73 au a Hormal 70 4 0 so Triggered y 0 0 Trigger Source E x l ource Load Custom Save Custom 51 zu 2 0 pe E gt za pee Frequency 2 o 50 Manual Control Moda 19 cO 0 0 y 4 0 Courte Input Logaritmi os 4 1 0 z C coute threshold C Linear 40 2 0 a 8192 7 Y Waveform Output E de al Trigg r Cyclos Enabled 28 Be on g 25 0 Disabled 32 Off 2 A Swi le E Pepzat 3 eque jeep 3 quency Sweep R 7 0 at 01 Disabled 10 0 ___ Man tal Trigger c 7 Sweep Mode PWM 1 Gutput SweepmMede Pattern Outaut Enabled 5 0 E 4 Logarthmic Enabled s Logarthmic Enabled Settine 1 E senses 2 E C linear Cisabled Lircar Disabled Figure 1 WGM 201 Graphical User Interface 1 4 Selecting Waveform When powering up the WGM 201 the waveform is initially set to Sine Other built in waveforms are Square Triangle and Sawtooth There are three buttons on the graphical user interface for controlling the custom waveform Load Custom loads some arbitrary waveform into the generator waveform memory and that waveform now appears at the output of the generator When you cycle the power that waveform is lost If you
6. host PC Waveform Generator Trigger Mode Free Running Triggered Output Continuous Tone Burst Source External Manual Counter input Counter Threshold Cycles On off repeat 1 2 Basic Operation In this section we assume that the sofware has been installed successfully The hardware is plugged into a USB port and the GUI indicates Connected On the hardware the left green LED indicates POWER The right is a dual LED which flashes with each command When connected to the GUI this LED lights more or less continuously 1 3 Graphical User Interface The full GUI is shown in figure 1 The main panel the core generator is on the left There are four subsidiary panels to the right each with an X closer in the upper right corner When the subsidiary panels are not being used they may be hidden to minimize screen space Click on the X closer in the upper right corner to hide a panel It is replaced by a button on the main panel Figure 2 shows all the subsidiary panels hidden Notice the buttons in the upper right corner they restore the subsidiary panels of xf FS Syscomp WGM 201 Tle View Toos tlordware ibp ERE se Waveform Generator PWM Controls x Pattern Generator x Counter X Trigger Controls x PWM Channel 1 Waveform Generator Reset Counter Met d C FreeRurniniy Frequency y Triggered 100000
7. is logic high during sweep up and logic low during sweep down This signal can be most easily seen when the Sweep Behaviour is set to Cycle Up Down On the main control panel set Frequency Sweep to Enabled The Frequency slider should move up and down and the output frequency change The sweep trigger signal then readily visible During Sweep Behaviour Sweep Up Repeat or Sweep Behaviour Sweep Down Repeat the logic level signal goes low for about 50mSec during the sweep reset 2 2 3 Sweep Trigger Input The sweep may be initiated by a logic level signal applied to the Counter Trigger BNC input connector on the front panel of the unit This can be useful in synchronizing the sweep generator to an external device such as an oscilloscope To trigger the sweep e In the Frequency Sweep Settings panel under Sweep Trigger select Counter Trigger Input e In the Counter panel under Trigger Level select a suitable level For example the default of 2 5 volts is appropriate for many logic level signals greater than 2 5 volts The trigger voltage may be larger than 5 volts as much as 10 volts Internal clamps will protect the trigger circuitry For example a 9 volt battery makes a convenient trigger signal Any of the Sweep Behaviour modes can be triggered In the Repeat modes Cycle Up Down Sweep Up Repeat Sweep Down Repeat one trigger initiates sweeps which will then continue indefinitely without further triggers In the Reset modes Swe
8. on a bit cell to change its state from zero to one or vice versa On the Bit 0 line create 7 logic ones in a sequence each separated by a logic zero On the Bit line create a single logic 1 in the 15 time slot The pattern editor should appear as in figure 8 Click on the floppy disk icon and save the file Return to the Pattern Generator panel and click on Load Waveform In the load dialog select the previ ously saved file The pattern should now appear at the rear panel connector Oscilloscope Vertical Controls Channel A Triggered Timebase Controls Trigger Controls l F 28 eje Trigger Mode Trigger Slope Trigger Source Figure 9 Pattern Demonstration The resultant computer display captured by a Syscomp CGR 101 oscilloscope is shown in figure 9 The upper trace shows 7 shift pulses in sequence The lower trace shows the single load pulse 11 5 2 Pattern File Format The pattern file is a text file so it can be edited in any text editor such as Notepad on a Windows machine The first entry is the number of time slots 16 in our example This is followed the one byte value for each time slot entry In our example the last entry is 2 because there is a single binary 1 on the Bit 1 line which has a binary weight of 2 12 6 Counter The Counter is a general purpose event and frequency counter In the Events mode the counter increments with each trig
9. 16 18 20 O O O O 0 O O O O Oo 1 3 5 7 9 11 13 15 17 19 0 1 2 3 4 5 6 7 A Digital Pattern Outputs WGM 201 Waveform Generator Rear Panel Connector View toward rear panel Figure 12 WGM 201 Rear Panel Connector Pinout The pinout is shown in figure 12 and on the case label of the instrument 10 1 Rear Panel Connector Mating Plug One suitable rear panel connector mating plug is as follows MODE part 35 0202 0 20 position 2 row 0 1 2 54mm contact spacing Mates with 20 way 0 050 spacing flat cable Polarizing key Centre bump Strain Relief Available from MODE Electronics http www mode elec com Distributed by Active Tech Electronics in Canada http www activel23 com Another suitable connector is this one 21 3M part D89120 0131HK Digikey part MKC20E ND 20 position 2 row 0 1 2 54mm contact spacing ates with 20 way 0 050 spacing flat cable Polarizing key Centre bump Contacts 10u gold plate Mating strain relief for this connector 3M part D3448 89120 Digikey part MESR20 ND Available from Digikey http www digikey com Any flat cable with 0 050 conductor spacing that will mate with IDC Insulation displacement connector should be suitable for use with these plugs For example 3M 3302 Series Digikey part MCM 20M 5 ND 5 foot length 10 colour repeat Clear carrier 11 Creating an Arbitrary Waveform The WaveMaker Waveform Editor is available under the Tool
10. 493 5 kHz Above that frequency some addresses in the waveform memory are skipped As a result the waveform contains fewer than 256 horizontal points At very high frequencies the number steps in the waveform decreases to the point that the waveform steps become visible The waveform becomes blocky There is a tradeoff between the quality of the waveform and the maximum useable frequency of operation In this generator the default maximum frequency seen at the top of the frequency slider has been set at 3MHz This is under the control of the user Click on that display and enter a new maximum value Quite satisfactory sine waves can be obtained at 10MHz 7 2 Detail in Arbitrary Waveforms The basic nature of a sampled data system the lowpass filter in the signal chain places a restrictions on the shape of the arbitrary waveform The highest frequency content in the arbitrary waveform cannot exceed the capability of the output amplifier in the generator As a rule of thumb the highest reproduced frequency should be less than the maximum generator sine wave frequency which is 10MHz For example suppose the arbitrary waveform consists of a four cycles of a sine wave When the frequency is set to 1OMHz the effective output frequency is 40MHz which is beyond the capability of the generator output amplifier You are free to experiment with this to see if the generator can reproduce the required detail at the maximum operating frequency
11. WGM 201 Waveform Generator Manual http www syscompdesign com Version 1 08 September 3 2012 Revision History Version Date Notes 1 00 Oct 2009 First revision 1 01 May 2010 Added section on arbitrary waveform Added directions for waveform sync 1 02 May 2010 Added command information 1 03 Dec 2010 Added sweep modes 1 04 Mar 2011 Added WaveMaker reference Added Triggered Tone BurstExample 1 05 Apr 2011 Added more command information 1 06 Aug 2012 Corrected Enable Disable command 1 07 Sep 2012 Added terminal emulator notes 1 08 Added command example Contents 1 Overview 1 1 Specificato e kb Alege ange a aoa ee Geeta eke Mier ER Ges GS Gece 1 2 Basic Operation s sars kes eae Tae ate ak Go ES is See on oe a e 1 3 Graphical User Interface 2 tau tashina s odere yi sia 1 4 Selecting Waveforms su of DS rs a amp een wes 15 Manual Frequency Setting saos sesaat y a eea e aaea a e a a a a a a a 2 Frequency Sweep 2 1 Manual sweep s eiee eee eeta e ad beta E ede e ee we 2 2 Automatic SWEEP s sp mr ORES A A 22 1 Contunuous SWEEP is o A SHG OE OWS EE 22 2 Sweep Migger Output ns doae 4a 8 is RAO oe we we OR 22 3 Sweep Tngecrinpit 222 29 cc baw bee ee Gee bee ene de be eee ee 3 Tone Burst 3 1 Triggered Tone Burst pia ts A A SEES BS Bee ee BS oie 4 Pulse Generator 5 Pattern Generator 5 1 Creating a Digital Pattern oro a o a A aS D2 Pattern File Format s s se gas eias fo ee a Slee eee debi bee Vee ee w
12. and tone burst However any generator that can produce a suitable trigger signal may be used to provide the signal Any oscilloscope may be used to observe the trigger and tone burst 1 8 Start both the CGR 101 software and WGM 201 software The screen will be rather crowded at that point You can minimize the program you are not using at any given instant You can also minimize the Pulse Controls and Pattern Generator panels of the WGM 201 since they are not needed for this exercise The tone burst trigger signal originates in the CGR 101 Connect the CGR 101 generator output to Channel A of the CGR 101 scope so that you can see the trigger signal Connect that same signal to the front panel counter trigger input BNC connector on the WGM 201 generator At the trigger source the CGR 101 generator set a waveform frequency of about 20Hz or so to start with Set the amplitude to 55 1V and the waveform to square wave Trigger the scope from this signal Check that this signal appears on Channel A of the CGR 101 oscilloscope Connect the output of the WGM 201 generator to channel B of the CGR 101 scope Check that WGM 201 waveform generator trigger is operating properly e On the Counter panel Counter Mode select Event e On the same panel adjust the trigger slope and level until you see the counter readout at the top of the panel incrementing Set up the Trigger Controls panel Waveform Gener
13. arithmic or linear The frequency may be set to sweep manually or automatically between the two limit frequencies with ad justable sweep rate and frequency increment Core Waveform Generator Architecture Direct Digital Synthesis DDS Clock rate 134MHz Waveform Vertical resolution 8 bits independent of amplitude or offset Amplitude 10Vp p max adjustable with 8 bit resolution Offset 10V max adjustable with 8 bit resolution Maximum output 10V signal plus offset Output impedance Sine wave signal Noise Square wave rise and fall time Waveform timebase Types Arbitrary waveform Noise waveform 150 ohms gt 48db S N independent of output amplitude or offset 24nSec 256 points Sine square triangle ramp noise arbitrary 8 bit vertical by 256 time points Digital 32 bit sequence generator clock 134 208MHz Frequency Range sine 0 031Hz to 1OMHz resolution 0 1 Hz Range others 0 031Hz to 1OMHz resolution 0 1 Hz Resolution 0 031Hz Control Manual or automatic sweep Control curve Frequency limits Linear or Logarithmic characteristic Minimum and maximum frequencies are settable Frequency sweep Mode Linear or logarithmic characteristic Direction Initial direction up down start top bottom frequency Sweep time step 250mSec to 5000mSec per step Sweep step magnitude User entered linear increment or log multiple Others Output Enable disable Computer control All controls are remotely operated from the
14. ator Trigger Mode Triggered Waveform Generator Output Mode Tone Burst Pattern Generator Trigger Mode shouldn t matter Trigger Source Counter Input Do not select External that inputis on the rear panel of the WGM 201 and accepts a logic signal Fora tone burst of 3 on 2 off set On 3 Off 2 Repeats 1 Set the WGM 201 waveform generator amplitude output to 18 1V frequency to 112 Hz or so On the oscilloscope display you should see a burst of 3 cycles coincident with the rising edge of the square wave trigger with very little delay between the trigger signal and start of the tone burst Now that you have a basic tone burst configuration operating you can change the control parameters to the values you want 4 Pulse Generator The instrument has two independent pulse generators For each generator the duty cycle and frequency can be set independently That is changing the duty cycle has no effect on the frequency and vice versa The duty cycle is defined as the ratio of ON time to the period of the waveform During the ON time the waveform is at 5V During the re mainder of the period the OFF time the waveform is at zero volts PWM Controls x PWN Channel 1 Frequency 100000 e Adjusting duty cycle independent of frequency is useful when test ing certain types of switch mode power supplies and power control circuits e An adjustable duty cycle waveform may b
15. axi mum pattern frequency to keep the sample rate below 10MHz 1 e The maximum frequency for a 1024 sample pattern is 20kHz 40kHz for a 512 sample pattern 80kHz for a 256 sample pattern etc The rear panel pattern generator trigger signal goes to logic low at the beginning of each sequence and high approximately half way through the sequence This is true for any pattern length As in the core waveform generator and pulse generator con Figure 7 Pattern Generator Control Panel trols the frequency may be set by direct entry click on the fre quency display by dragging the slider or by clicking in the slider area outside the button The maximum and minimum frequency settings may be changed by clicking on them and entering new values 5 1 Creating a Digital Pattern We ll use an example to illustrate this process We assume that our digital logic needs 7 shift pulses on one pin followed by a load pulse on another pin 1 Click on the Pattern Generator panel Edit Waveform button 2 The pattern editor panel displays 3 Click on the pattern editor blank sheet icon 4 The New Waveform Select Sequence Length panel appears Select the desired sequence length in this case we select a sequence length of 16 5 The pattern editor panel displays 8 traces with timing marks from 0 to 15 10 NO 0 N QQ 11 Figure 8 Pattern Editor Click
16. byte first Notes 1 A volatile sample is one sample of the arbitrary waveform It is volatile because it is held in RAM so it disappears when the power is disabled A total of 256 8 bit samples constitute a waveform and will show as the current output waveform A semi permanent sample is written into the hardware EEPROM It does not appear immediately in the output waveform It is transferred into the waveform RAM and appears in the output with the Select waveform User command W 4 2 Enable Waveform output enables and disables all waveforms including noise Enable Noise enables and disables only the noise source When noise is enabled other waveforms such as Sine are disabled and vice versa 0 DUB uwyNn OoO Converting Frequency Here we show the example of converting output frequency of 2MHz into a command 18 1 Convert the desired output frequency into the correct count using the conversion factor 2 x 10 Hz 0 031247735 Hz Count 64004639 Counts 2MHz 2 Convert this value to a hexadecimal number Some scientific calculators have this function or use the web site http www statman info conversions hexadecimal html 64004639 base 10 3d0a21f hexadecimal base 16 3 Group the hex number by pairs starting at the right end Convert each pair to the corresponding decimal number which will range from O to 255 Again use a calculator for each pair or the website mentione previously 3d0a21f 3d0a2 If
17. cate with the WGM 201 hardware 9 1 Setting up the Terminal Overview We recommend first testing the connection using a terminal emulator A terminal emulator such as Hyperterminal in Windows or Seyon or Minicom in Linux can be used to send commands to the hardware and this verifies that the serial connection is working properly When the WGM 201 software is running correctly ie Connected actuate Hardware gt Connect gt Port Settings and determine the COM port serial port being used by the GUI graphical user interface Shut down the GUI so that it s not trying to use the serial port The serial port needs to be available to the terminal emulator program Start the terminal emulator and connect to that COM port On a Linux machine it s probably a tt yUSBx port where x is the number of the port Set the terminal emulator parameters to 8 bits no parity one stop bit Since the serial port is a VCP virtual COM port that is actually USB the baud rate is unimportant With the WGM 201 hardware connected you should now be able to send commands to the hardware The first command to try is the Ident ify command Send i followed by a carriage return The right hand LED on the hardware should flash since the hardware received a character and has sent a string The identification string see table below should appear on the terminal screen 9 2 Terminal Emulator under Windows Some versions of the Windows operating system have Hyp
18. duces a series of frequencies stepping from one to the next This control sets the time inter val between frequency steps ranging from 50mSec to 5 seconds A slower sweep is required for example when sweeping a device with a high Q resonance Choose the Frequency Step Setting For a linear sweep click on the Linear Step button and enter the frequency increment between each out put frequency For example if this is set to 10 then the frequency will increment by 10Hz with each new output For a logarithmic sweep click on the Logarithmic Step button and enter the frequency increment between each output frequency For example if this is set to 1 2 then each new frequency is 1 2 times the previous frequency This produces output frequencies that are equally spaced on a logarithmic frequency scale Select the Initial Sweep Direction Up or Down This control only applies for the Sweep Behaviour Cycle Up and Down It is disabled for all other Sweep Be haviour settings Select the Sweep Behaviour Cycle Up Down sweeps at the same speed when increasing and decreasing frequency Sweep Up Reset sweeps increasing in frequency and then resets to the starting frequency waiting for a trigger signal To trigger the sweep manually Move to the Frequency Sweep Settings pannel Sweep Trigger section Select Manual Enable Disable Move to the main waveform generator screen Frequency Sweep controls Click on Enabled The sw
19. e burst Trigger Cycles Off sets the number of cycles between bursts Trigger Cycles Repeat effectively sets the number of tone bursts The total number cycles is constrained according to the follow ing Non Noff x Nrepeats lt a where Non is the number of ON cycles in each burst Nos f is the number of OFF cycles in each burst Nrepeats is the number of tone burst repeats A tone burst is best observed with a digital storage oscilloscope set to Single Shot On the generator set up the tone burst configuration as above Set the scope to single shot triggering Reset the scope sweep Actuate Manual Trigger on the generator The scope should capture the desired tone burst Oscilloscope Vertical Controls Triggered Timebase Controls Trigger Controls a 2 to Trigger Mode Trigger Slope Trigger Source 2 4 Single Shol Plus a a 3 1 Single Shot Reset Manual Trager Figure 5 Tone Burst Oscilloscope Display Figure 5 shows these tone bursts captured by a Syscomp CGR 101 CircuitGear oscilloscope in single shot mode 3 1 Triggered Tone Burst It is possible to use an external trigger signal to initiate each tone burst from the WGM 201 generator Here is an example configuration In this example we describe a configuration using the CircuitGear CGR 101 generator to provide the trigger signal and the CircuitGear CGR 101 oscilloscope to display both the trigger signal
20. e used as the basis for digital to analog conversion If the waveform is low pass filtered the resultant average is proportional to the duty cycle e Spectrum analysis of a variable duty cycle signal is illustrative of the princibles of Fourier Analysis Each pulse generator output has its own control panel figure 6 One of these control panels is visible at a time selected by a switch at the top of the panel which shows Channel 1 or Channel 2 Pulse generator output signals swing from OV to 5V The two signals and ground connections are available on the rear panel connector of the instrument section 10 The pulse generator controls are identical for Channel 1 and Channel 2 The output is enabled or disabled by radio buttons under PWM or PWM2 Output When an output is disabled the frequency and duty cycle sliders are frozen As in the case of the core waveform generator the frequency may be set by direct entry Left click on the frequency display in the pulse generator panel This causes an entry widget to appear Enter the desired frequency and then left click on OK The frequency slider operates in the same manner as the core waveform generator The control may be dragged between the maximum and minimum values Clicking on the slider area outside the button causes the frequency to increment or decrement The maximum and minimum frequencies are set by clicking on their respective displays and typing in suitable values The Sweep Mode c
21. eep executes once as indicated by movement of the Frequency slider At the end of the sweep the indicator returns to Disabled Click on Enabled to repeat the sweep To trigger the sweep from an external signal see below Sweep Trigger Input section 2 2 3 Sweep Up Repeat sweeps increasing in frequency resets to the starting frequency and then re peats no trigger signal required Sweep Down Reset sweeps decreasing in frequency and then resets to the starting frequency waiting for a trigger signal To trigger the sweep manually see above Sweep Up Reset To trigger from an external signal see below Sweep Trigger Input section 2 2 3 Sweep Down Repeat sweeps decreasing in frequency resets to the starting frequency and then repeats no trigger signal required 2 2 1 Continuous Sweep If you selected Cycle Up Down Sweep Up Repeat or Sweep Down Repeat to start the sweep move to the main waveform generator screen Frequency Sweep controls Click on Enabled The generator will now sweep between the two limits The position of the Frequency slider moves to indicate progress of the sweep 2 2 2 Sweep Trigger Output When Enable Sweep Trigger Out PWM2 is checked a logic level sweep trigger signal is available at the PWM2 output terminal on the rear panel connector This signal could be used by an oscilloscope to cause the beam of the scope to start at the same time as the beginning of a frequency sweep The signal
22. ep Up Reset Sweep Down Reset one trigger initiates one sweep and reset During the frequency sweep the Frequency slider moves and the Disabled Enabled button on the main panel changes from Disabled to Enabled 3 Tone Burst These controls are in the Trigger Controls panel figure 4 Trigger Controls x e For normal continuous waveform output operation of the generator f set Trigger Mode to Free Running and Output Mode to Continuous deca This is the power on default setting FreeRunning i Triggered e For continuous generation of tone bursts set Trigger Mode to Free dci Wavetorm Generator Running and Output to Tone Burst The tone burst pattern is speci Output Mode fied by the Trigger Cycles On Off settings Trigger Cycles On sets Continusus the number of complete cycles in the burst Trigger Cycles Off sets Cone Burst the number of cycles between bursts Trigger Cycles Repeat has no Palen Generar effect The maximum count for Trigger Cycles On and Trigger Cy Trigger Mode cles Off is 65535 normal Triggered Trigger Source Eterna 6 Manual Counter Input Counter Thresrold 8132 T e For manually triggered generation of a tone burst set Trigger Mode to Triggered and Output Mode to Tone Burst Set Trigger Source to Manual The tone burst pattern is specified by the Trigger Cycles On Off set tings Trigger Cycles On sets the number of complete cycles in th
23. erterminal installed which can act as a terminal emu lator However Hyperterminal does not provide convenient access to the setup parameters and is difficult to use We installed and used the open source software TeraTerm instead 1 Download and install the TeraTerm software from Sourceforge http en sourceforge jp projects ttssh2 releases This should create a TeraTerm icon on your desktop 2 Plug in the WGM 201 hardware to an unused USB port 3 Start TeraTerm The New Connection window appears TCP IP is selected by default Change the selection to Serial 4 On that same window select Port In this case it shows COM3 and COM5 USB Serial Port Select COMS Click on OK Window closes 5 Select the menu item Setup gt Serial Port The port has been selected no need to change that Set the Baud Rate to 230400 Set Data Bits to 8 Set Stop Bits to 1 Set Parity to None This is triggered operation not a phase lock Changing frequency requires changing frequency on both master and slave 3On the todo list is a control for jogging the phase of the two waveforms 15 Set Flow Control to Hardware Click on OK Window closes 6 Select the menu item Setup gt Terminal Change the New line Receive to CR LF Change the New line Transmit to CR LF Click on OK Window closes 7 In the main terminal window type the letter i followed by the Return key You should see a message something like Syscomp Adva
24. ger pulse up to a max imum of 231 1 approximately 2 x 10 counts A manual reset restarts the counter from zero The counter input connector is the right hand BNC connector on the front panel In the Frequency mode the counter measures the input frequency to an accurancy of 50 ppm 0 005 Counter trigger controls allow one to select the slope of the trigger rising or falling edge and the voltage 5V approx The counter input signal processed by the trigger slope and level can be used to trigger a tone burst Select Trigger Source Counter Input This same trigger signal can be conditioned to delay a number of se lected cycles For example one could set up the generator to produce a tone burst when 1000 events have occurred Select Trigger Source Counter Threshold Click on the numbered button below Counter Threshold An entry widget pops up Enter the number of cycles in that entry Counter threshold triggers only once and then must be manually reset 7 Arbitrary Waveform A waveform for the WGM 201 is stored as a text file consisting of 256 8 bit bytes with a dat suffix Look for sine dat as an example Most negative value of a waveform is coded as 255 Most positive value is coded as 0 Any program that can create this type of file can be used to create wave form For example you could hand code the file using a text editor pro gram like Notepad although this would be rather tedious If the wavefor
25. m can be described by a formula then you can use a spreadsheet to create the necessary file Use the formula to create 256 values of the waveform such that all the values are in the range 0 lt x lt 255 Copy the waveform values to a new sheet Save that sheet as a csv format file Review the file in an editor and remove any extraneous characters by search and replace When creating and generating an arbitrary waveform Keep in mind the constraints described in sections 7 1 and 7 2 below 7 1 Low and High Frequency Settings At low frequency the waveform memory address remains constant for a number of clock cycles As a waveform is produced all the addresses in the waveform memory are accessed in ascending order each for several clock cycles Consequently the waveform includes 256 horizontal steps At some intermediate frequency each and every clock pulse results in an increment of the waveform address Each point on the waveform is produced exactly once At this frequency call it fmia the period of the generated waveform call it Tmia is given by Tmid Points in one waveform x Telock 2 x 600 nsec 154usec This period corresponds to a frequency of 1 Tmid Fmiad 13 Counter x 0 Reset Counter Counte Mode Zounter C Frequency Polarity Positivs Rising Negative Faling Trigger Leve 10 3 9 3 a J 72 6 3 5 43 Figure 10 Counter Panel 1 154usec 6
26. nced Waveform Generator V1 0 1 0 If so you are now connected and can issue commands to the generator Notice that all commands are terminated by the Return key 8 Example The command A 128 sets the amplitude to 5 volts Example The command W 1 sets the waveform to Triangle 9 3 Command Listing The commands that are used to control the WGM 201 hardware are shown in the following tables All commands are terminated by a carriage return character A terminating line feed character is ignored cent Pe CSE i Identification string request Returns Syscomp Advanced Waveform en Generator VX XX where X XX is the firmware revision Function Generator Amplitude sets peak voltage of waveform Usage A nnn where nnn is an 8 bit ascii number ranging from 0 to 255 representing the amplitude Output amplitude nnn 255 x 10V Example A 127 sets the amplitude to 5 volts Frequency Command Usage F aaa bbb ccc ddd where aaa through ddd are 8 bit ascii numbers that make up a 32 bit number YYYY to set the output frequency Output frequency YY Y Y 0 031247735 Hz See below for an example Offset command Usage O nnn where nnn is an 8 bit ascii number representing the offset Output offset 127 nnn 127 x 10V Write volatile 1 waveform sample into device a eight bit address d eight bit data Write semi permanent 1 waveform sample into device buffer memory a eight bit address d eight bit data Recall wavefo
27. ontrol characteristic may be selected as logarithmic or linear A second slider sets the duty cycle of the output waveform In general the pulse generator outputs are unsynchronized with each other and the main generator output However if the two pulse generator frequencies are set to the same value they will remain in a fixed although arbitrary phase relationship This is also true if one pulse generator output frequency is an integer multiple of the second output The two frequencies can also be made to walk with respect to each other For example if one frequency is set to 400 0 Hz and the other to 400 1 Hz then the two frequencies will appear to drift past each other one complete cycle every 10 seconds Similarily the two pulse generator outputs will synchronize with the main output if they are set to exactly the same frequency 5 Pattern Generator PS The pattern generator produces a series of 8 bit data words at the rear panel connector section 10 on page 21 The sequence length may be any binary value from 4 to 1024 words The pattern generator is controlled from the Pattern Generator Control Panel figure 7 The frequency slider sets the frequency of the repetition rate of the sequence For example if the sequence length is set to 32 words and frequency slider set to 1000Hz then the 32 word sequence will repeat 1000 times per second The maximum bit toggle rate is 10MHz The software automatically calculates and adjusts the m
28. ow ase 6 Counter 7 Arbitrary Waveform 7 1 Low and High Frequency Settings eee eee ee 7 2 Detail in Arbitrary Waveforms 2 0 noise anni ane 7 3 Wavetorm Editor o rines a a a a AA 8 Synchronizing Two Generators 9 Commands 9 1 Setting up the Terminal Overview 9 2 Terminal Emulator under Windows o o 00000 9 3 Command Listing os s soraa reau sda e 10 10 12 13 13 13 14 14 14 10 Rear Panel Connector 21 10 1 Rear Panel Connector Mating Plug o e e 21 11 Creating an Arbitrary Waveform 22 List of Figures 1 WGM 201 Graphical User Interface 2 o e e 3 2 Minimum User Interface gas seo da in ds ODS a A 4 3 sweep Mode Control Panel 2000 32 urn orienta Ce eS ee RE ES 4 4 Trigger Controls Panel 2 52554 4085 64504 E eka Hb 6 5 Tone Burst Oscilloscope Display oo e 7 6 Pulse Generator Control Panel ses e044 a di o SOU e 8 7 Pattern Generator Control Panel s 400 petsa peep p E be ee we 10 8 Pattern Editor lt oak be e Oe Eee eS Ee Se hed bed ee 11 9 Pattern Demonstration y ese vs ee ee Re OA A a eS 11 10 Counter Panel lt 3 s eric hy e es BA Ee ts HS EE Ee ds ea 13 11 Synchronized Waveforms 2 5 2 4 ma Re ee PS Ea Re eS aS 14 12 WGM 201 Rear Panel Connector Pinout 2 2 21 lil 1 Overview The Syscomp WGM 201 Waveform Generator is a general purpose waveform generator 8 bit digital word gen e
29. rator and general purpose counter With many advanced features it is useful for the teaching development and debugging of electronic circuits The WGM 201 is one of a series of instruments from Syscomp Electronic Design All instruments use a computer host for the graphical user interface GUI control panel and connect with the hardware via a USB virtual COM port The software is Open Source and runs under Windows Linux and Mac operating systems The generator hardware receives power from the host PC via the USB connection so that no other power source 1s required The generator hardware is capable of producing a variety of waveforms Sine square triangle and ramp saw tooth waveforms are installed in the firmware In addition an arbitrary waveform can be created and downloaded into the generator The generator can produce these waveforms at frequencies between 0 1Hz and 10MHz with variable amplitude and variable DC offset The waveform frequency is derived from a crystal oscillator so it is precise and stable The waveform ampli tude is determined by digital analog conversion of digital values The amplitude stability is determined by internal voltage reference source and 1 resistor values A PC host displays a graphical user interface for the function generator with frequency readouts sliders clickable buttons and various other controls The PC connects to the function generator hardware via a USB cable so that no other power source is req
30. rm from the non volatile memory Enable noise output 2 mooo Disable noise output J E Select waveform where n is one of the following 0 Sine 1 Triangle 2 Square 3 Sawtooth 4 User o IE pe N A F Wn Sad ad U N n 16 Trigger Commands PWM Commands Pen Geabcd Select trigger mode where n is one of the following 0 Waveform Generator Free Running Mode 1 Waveform Generator Triggered Mode 2 Pattern Generator Free Running Mode 3 Pattern Generator Triggered Mode Select continuous output Select trigger source where n is one of the following 0 External Trigger 1 Manual Trigger 2 Counter Trigger 3 Counter Input Set trigger count command Parameters a and b make up a 16 bit number which determines how many waveform or pattern generator cycles are executed in triggered mode Set tone burst ON cycles Parmeters a and b make up a 16 bit number which determines how many waveform cycles are output in tone burst mode Set tone burst OFF cycles Parmeters a and b make up a 16 bit number which determines how many waveform cycles the generator is idle in tone burst mode Counter trigger threshold command Parameters a b c d make up a 31 bit threshold value for the counter Byte a is the MSB byte d is the LSB When the counter value exceeds this threshold a counter trigger is generated which can be used to trigger the waveform generator or pattern generator PWM Duty Cycle
31. rol M1 Select trigger mode 1 Triggered mode Y 255 255 Number of repeat cycles see below X 1 Select trigger source 1 Manual trigger T Execute manual trigger To calculate the number of repeat cycles number of output cycles per trigger the 16 bit register setting is given by 65536 Number of cycles eg For three output cycles Register Setting 65536 3 65533 This value is sent to the hardware in two 8 bit bytes a high byte 255 and a low byte 253 The command is then Y 255 253 eg For one output cycle Register Setting 65536 1 65535 The command is Y 255 255 20 10 Rear Panel Connector The rear panel connector provides access to the following signals Digital Pattern outputs O through 7 Trigger signals for the waveform generator pattern generator and counter Waveform Trigger Out A logic level signal that goes high at the beginning of each waveform It goes low at approximately the mid point of the waveform Pattern Generator Trigger Out A logic level signal that goes low at the beginning of each pattern sequence It goes high at approximately the mid point of the pattern Counter Trigger Out A logic level signal that corresponds to the counter trigger signal e Pulse Generator outputs 2 e External trigger input e Ground Counter Trigger Out PWM1 out Pattern Generator Trigger Out PWM2 out Waveform Trigger Out GND External Trigger In Key 2 4 6 8 10 12 14
32. s menu Select that item and the blank waveform edit screen pops up For WaveMake instructions select the Help gt Manual PDF on the waveform edit screen If for some reason that fails check in the install directory Source subdirectory The manual file should be there as a pdf which you can open with Acrobat reader Contributed by John Foster Thanks John 22
33. tput Disable pulse generator 1 Output 2 Enable pulse generator 2 Output Disable pulse generator 2 Output 19 Pattern Generator Enable pattern generator output Disable pattern generator output Pattern generator frequency See frequency command Bhld Pattern generator sample command Parameters h and are the high and low bytes of a 10 bit address value Parameter d is an 8 bit sample value ETE A C Counter threshold Usage C nnn where nnn is an 8 bit ascii number representing the counter threshold voltage Threshold voltage 127 nnn 127 10V r byte first Reset counter to zero T Select positive counter trigger polarity Select negative counter trigger polarity Example Single Cycle Tone Burst Read counter Command returns 5 bytes Cuvwx where uvwx correspond to a 32 bit counter value high Here we show the generation of a single cycle tone burst from commands to the hardware We determined the commands by executing them on the GUI by hand while reading the ASCII strings that the host PC was sending to the hardware Here is the manual operation 1 Start GUI 2 Set output amplitude and waveform and frequency if required 3 Select Triggered under Waveform Generator Trigger Mode 4 Select Manual under Trigger Source 5 Set Repeat under Trigger Cycles to 1 6 Press the manual trigger button to generate one cycle Here are the corresponding commands A 128 Amplitude cont
34. ude is measured in decibels another logarithmic scale and the frequency is a logarithmic scale This simplifies interpreting the result of a frequency sweep 2 2 Automatic Sweep The WGM 201 can automatically sweep the output frequency over its entire frequency range or some part thereof Frequency Sweep lolx Signal generators of the past have used an approximation of the logarithmic control Sheep ttoakange ed the frequency in multiples of 10 and a Tune knob which varied the frequency in a linear fashion over each range URSS Svas8fenerally limited to a range of 10 1 A few special purpose instruments could sweep the audio band z NP6KBz a range of 1000 1 The WGM 201 i Ta has a maximum sweep range of 10 1 and can also sweep over a very narrow range Logarithmic Frequency Time Step ms 4 1000 L Frequency Step Settings Linear Step 1 Click on the upper frequency limit at the top of the fre quency slider and enter the maximum frequency of the sweep in Hertz eg 20000 Click on the lower frequency limit at the bottom of the frequency slider and enter the minimum frequency of the sweep in Hertz eg 20 Click on the Sweep Settings button to open up the Fre quency Sweep Settings control panel figure 3 In the Frequency Sweep Settings control panel Select Linear or Logarithmic sweep Logarithmic is most useful Select the Frequency Time Step using the slider The generator pro
35. uired A Graphical User Interface the GUI program for operating the waveform generator is provided on the ac companying CDROM The program is written in the Tcl Tk language It is completely Open Source so it may be modified and distributed freely The USB interface emulates a serial port so that it may be accessed as a serial port device from a host computer Any language that can talk to a serial port can send commands to and receive data from the hardware unit 1 1 Specification The core waveform generator is uses Direct Digital Synthesis to create standard and arbitrary waveforms with accuracy based on a crystal oscillator Amplitude and offset are controlled by DAC hardware independent of the core waveform generator so that the waveform vertical resolution remains at 256 points regardless of amplitude or offset The waveform can be adjusted in frequency in steps of 0 03Hz more precisely 0 031247735Hz over a total range of 0 1Hz to 1OMHz sine or 3MHz all other waveforms The default upper limit is shown as 3MHz This may be changed by the operator Recommended maximum for a sine wave is 10MHz Recommended maximum for other waveforms square ramp triangle is 3MHz An arbitrary waveform may contain spectral content up to a maximum of 10MHz Maximum and minimum frequency can be set to any points within that range For example the range can be set as 20Hz to 20kHz for audio work The characteristic curve of the control may be set to log
36. want to save the waveform so that it survives a power off on cycle use Load Custom to load the waveform and then Save Custom to write that waveform into permanent memory in the hardware Thereafter you can select that waveform by pressing the Stored Custom button That waveform will remain available unless you overwrite it with a new waveform See section 7 on page 13 for more details on arbitrary waveform 1 5 Manual Frequency Setting There are three methods of setting the output frequency 1 Set the output frequency by moving the Frequency slider The output frequency is shown in the frequency readout display to the nearest 0 1Hz The total frequency range of the frequency slider is established by the maximum and minimum frequencies shown at the top and bottom of the slider Left click on one of these to enter a new value 2 Move the frequency slider incrementally up or down with a left click in the track area the non button area of the frequency slider 3 Left click on the frequency readout display A data entry widget pops up Type in the desired frequency Left click on OK 2 Frequency Sweep Frequency may be swept manually or automatically ES Syscomp WGM 201 Ns Fie View Tools Hardware Help etd el PWM f Patter Courter Trigger Waveform Generator nd 3000000 Frequency Control Mode oo 03 El 4 Logerithmic 45 4 10 linear 20 3 30
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