CV Interface and Function Generator: Difference between revisions

CV Interface and Function Generator (view source)

Revision as of 11:14, 26 February 2020

2,333 bytes added , 26 February 2020

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Jo El

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 Hardware fully set up, now it's time for the digtal stuff.
 Our basic idea responds into the simple function to express the XY-Axis of the Joystick as 2 Values that are linearly mapped onto Out CV1 and Out CV2. So one axis gave us values between 0 and ~25000, which we simply mapped onto 0-10V. The following was to make a function which is summing the two axis into one value. We simply wrote a average function which, when activated, sums the the two Joystick values and maps them once again to 0-10V. We called this "Sum-Mode" and its accesible through pushing the joystick button one time. The State of these two Modes is indicated through the blue LED (on - SumMode [Out CV 1 = Out CV 2] , off - NormalMode [Out CV 1 = X-Axis ; Out CV2 = Y-Axis]). So the second CV Output becomes a copy of the first when the SumMode is active. So this Mode could also be used as a multiple.
+To not get users confused its important to say that these are global modi, which works both same way with the following (local) modes.
+These are the Local Modes so far:
+. Sine LFO
+. Sample and Hold internal
+. Simplex Noise
+. Sample and Hold external
+The idea of these modes is to mix the voltage generated by the Joystick with different functions. Or, in other words, to make the joystick controlling an offset to different functions.
+...
+Conclusion
+This circuit is really a raw prototype, so there are many things to mention.
+Its extremely important to add a voltage limiting circuit with diodes to both CV/Clock Inputs because right now a voltage over 11V or below -1V could damage the ADC board. Though signals over 10V are pretty uncommon in modular synthesizers and eurorack, bipolar signals from -5V to 5V or even -10V to 10V are not.
+So for the harmless and free use of the CV input there need to be such circuit. As well as an additional OpAmp Buffer for those inputs.
+Then there need to be functionality added to the CV Input, because right now its only possible to use 1 Input as Gate Input for clocking the Sample Hold external Mode. But there are many uses for such Input. One could just be voltage conversion, so when the device is connected over usb, the, now digital data could be send via serial connection to other software as "Processing". Another way would be to implement OSC protocol to the code and make this incoming Voltage available as OSC data for the reuse by other software applications.
+Another way to use the CV input would be the modulation of internal parameters. For example the rate of the Sine LFO in that Mode(1) or the bitReduction Amount Parameter of the Simplex Noise Mode(3).
+Or, simply to add an offset by the joystick to an incoming signal.
+At this point it's right to mention that the parts we choose for our circuit are not really fitting each other. Because when we receive a incoming signal at 16Bits, process it in any way, and then send it out at 12Bits,  there is an enourmous amount of quality loss because of the resolution drop. So, perspectively it makes much more sense to use the same Resolution for the DAC's and ADC's. Or at least an higher Resolution on the DAC then on the ADC. So in the future we will exchange the current 12Bit DAC by an 16Bit DAC.