Aux ADC controlled VCO

SigmaDSP & SigmaStudio Vincent.Bruinink Oct 10, 2011 00:00 2 replies Original on forum ↗

Vincent.Bruinink Question

Oct 10, 2011 00:00

Hi,

I`m trying to implement a Aux ADC controlled VCO that should generate a sine wave from aprox DC to 10Hz.

Do I have to use the lookup table to convert the 8bit ADC value to the corresponding 5.23 values? So that the VCO

can be set between DC and 10Hz? Or is there an alternative way to convert the ADC result to corresponding values?

Best regards,

Vincent.

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ADIApproved Reply

Oct 10, 2011 00:00

Hi Vincent,

The 8 bit ADC will generate a number in the DSP between 0 and 1. If this number is passed directly to the VCO the output freq range will be 0 - 24Khz (assuming a 48Khz sample rate) so you will need to scale the output range of the ADC if you wish to only have the VCO between 0 and 10Hz. You can do this by multiplying the ADC output by a fixed number, which in this case is 10Hz / 24000Hz = 0.000416666 and then passing the result to the VCO. I've attached a project file that generates the correct VCO output range thru the DAC. At such low DAC output freqencies make sure the coupling cap is large enough to pass the signal through.

Best Rgds,

Alan

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Vincent.Bruinink Reply

Oct 11, 2011 00:00

Hi Alan,

Thank you for the example. Until now, I dit not know that the DC block could be used as a constant value. Things are clear now :-)

The VCO will be used to control the Delay block (Chorus).

Best regards,

Vincent.

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