DDS.h

#ifndef DDS_H_

#define DDS_H_

/// <summary>

/// Author: Florian Asal

/// Date: 2012.10.17

///

/// Using an adc speed of 48000Hz, which means that we can output 48000 values per second. To save storage

/// The output buffer is defined with a size of 960. Therefore we have to call the function 50 times a second

/// 48000/960 = 50  So using the DDS-Method with a frequency of 100, we are going to get 2 sine oscillations in

/// the output buffer. Multiplied by 50 = 100 waves per second => 100Hz.

///

/// While using this configuration (48000/960), a minimum LUT_SIZE of 120 is required, so that at 100Hz only one value

/// has to be interpolated between the samples:

/// frequency tuning word >= 0.5 => LUT_SIZE = jumpSize * F_CLK / (2*f_min) = 0.5 * 48000 / 200 = 120

/// </summary>

/// <summary>

/// Size of the LUT for the sine

/// Requirement: at minimum frequency at maximum one sample value is allowed be interpolated

/// between the samples of the harmonic oscillation stored in the table.

/// => frequency tuning word >= 0.5 => LUT_SIZE = jumpSize * F_CLK / (2*f_min) = 0.5 * 48000 / 200 = 120

/// </summary>

#define LUT_SIZE 120

/// <summary>

/// Size of the output buffer

/// </summary>

#define OUT_SIZE 960

/// <summary>

/// ADC-speed - according to shannon, this frequency has to be twice as big as the maximum output frequency

/// </summary>

#define F_CLK 48000

//Prototypes

void DDS_init(void);

void DDS(Int16 *, double, Int16);

double Lanczos(double);

#endif