diff --git a/dds.vhd b/dds.vhd index 9224d52..2c2c61b 100644 --- a/dds.vhd +++ b/dds.vhd @@ -28,7 +28,7 @@ entity dds is freq_res: natural:=17; -- width of frequency input (log2(max_freq)) adc_res: natural:=12; -- width of the ouput signal (=adc resolution) acc_res: natural:=32; -- width of the phase accumulator - phase_res: natural:=15); -- effective phase resolution for lookup tables + phase_res: natural:=10); -- effective phase resolution for sin lookup table Port ( clk : in STD_LOGIC; freq : in unsigned (freq_res-1 downto 0); form : in unsigned (1 downto 0); @@ -40,13 +40,16 @@ architecture Behavioral of dds is signal idx_phase : unsigned(phase_res-1 downto 0) := (others => '0'); signal amp_rect, amp_saw, amp_tria, amp_sin : unsigned (adc_res-1 downto 0); - type storage is array (((2**phase_res)/4)-1 downto 0) of unsigned (adc_res-2 downto 0); + --type storage is array (((2**phase_res)/4)-1 downto 0) of unsigned (adc_res-2 downto 0); + type storage is array (((2**phase_res))-1 downto 0) of unsigned (adc_res-1 downto 0); function gen_sin_wave return storage is variable temp : storage; begin forLoop: for i in 0 to temp'high loop - temp(i) := to_unsigned(integer(real((2**(adc_res-1))-1)*sin((real(i)*MATH_PI/2.0)/real(temp'high))),adc_res-1); - end loop; + --temp(i) := to_unsigned(integer(real((2**(adc_res-1))-1)*sin((real(i)*MATH_PI/2.0)/real(temp'high))),adc_res-1); + temp(i) := to_unsigned(integer(real(2**(adc_res-1) -1) + real((2**(adc_res-1))-1)*sin((real(i)*MATH_PI*2.0)/real(temp'high))),adc_res); + + end loop; return temp; end function gen_sin_wave; constant sin_wave : storage := gen_sin_wave; @@ -72,7 +75,8 @@ begin - --idx_phase <= idx(acc_res -1 downto acc_res - phase_res); + idx_phase <= idx(acc_res -1 downto acc_res - phase_res); + amp_sin <= sin_wave(to_integer(idx_phase)); -- Modulo is only required to prevent a synthesizer warning, but the value is actually never > 2**phase_res/4 --amp_sin <= to_unsigned((2**(adc_res-1)) - 1,adc_res) + sin_wave(to_integer(idx_phase) mod ((2**phase_res)/4)) when idx_phase(phase_res-1 downto phase_res-2)="00" else