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This commit is contained in:
Davide Cavagnola
2025-05-27 17:42:40 +02:00
parent d1cfa6443b
commit 82d76e48d8
15 changed files with 1626 additions and 1047 deletions
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LAB3/src/LFO_1.vhd
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@@ -5,100 +5,129 @@ USE IEEE.STD_LOGIC_1164.ALL;
-- arithmetic functions with Signed or Unsigned values
USE IEEE.NUMERIC_STD.ALL;
-- Entity: LFO (Low Frequency Oscillator) - Alternative Implementation
-- Purpose: Applies tremolo effect to audio by modulating amplitude with a triangular wave
-- This is a simplified, single-process implementation compared to the pipelined version
-- Provides real-time audio amplitude modulation for musical effects
ENTITY LFO IS
GENERIC (
CHANNEL_LENGHT : INTEGER := 24;
JOYSTICK_LENGHT : INTEGER := 10;
CLK_PERIOD_NS : INTEGER := 10;
TRIANGULAR_COUNTER_LENGHT : INTEGER := 10 -- Triangular wave period length
CHANNEL_LENGHT : INTEGER := 24; -- Bit width of audio samples (24-bit signed)
JOYSTICK_LENGHT : INTEGER := 10; -- Bit width of joystick input (10-bit = 0-1023 range)
CLK_PERIOD_NS : INTEGER := 10; -- Clock period in nanoseconds (10ns = 100MHz)
TRIANGULAR_COUNTER_LENGHT : INTEGER := 10 -- Triangular wave counter length (affects modulation depth)
);
PORT (
-- Clock and Reset
aclk : IN STD_LOGIC; -- Main system clock
aresetn : IN STD_LOGIC; -- Active-low asynchronous reset
aclk : IN STD_LOGIC;
aresetn : IN STD_LOGIC;
-- LFO Control inputs
lfo_period : IN STD_LOGIC_VECTOR(JOYSTICK_LENGHT - 1 DOWNTO 0); -- Controls LFO frequency (joystick Y-axis)
lfo_enable : IN STD_LOGIC; -- Enable/bypass LFO effect
lfo_period : IN STD_LOGIC_VECTOR(JOYSTICK_LENGHT - 1 DOWNTO 0);
-- Slave AXI Stream interface (audio input)
s_axis_tvalid : IN STD_LOGIC; -- Input data valid signal
s_axis_tdata : IN STD_LOGIC_VECTOR(CHANNEL_LENGHT - 1 DOWNTO 0); -- Audio sample input
s_axis_tlast : IN STD_LOGIC; -- Channel indicator (0=left, 1=right)
s_axis_tready : OUT STD_LOGIC; -- Ready to accept input data
lfo_enable : IN STD_LOGIC;
s_axis_tvalid : IN STD_LOGIC;
s_axis_tdata : IN STD_LOGIC_VECTOR(CHANNEL_LENGHT - 1 DOWNTO 0);
s_axis_tlast : IN STD_LOGIC;
s_axis_tready : OUT STD_LOGIC;
m_axis_tvalid : OUT STD_LOGIC;
m_axis_tdata : OUT STD_LOGIC_VECTOR(CHANNEL_LENGHT - 1 DOWNTO 0);
m_axis_tlast : OUT STD_LOGIC;
m_axis_tready : IN STD_LOGIC
-- Master AXI Stream interface (audio output)
m_axis_tvalid : OUT STD_LOGIC; -- Output data valid signal
m_axis_tdata : OUT STD_LOGIC_VECTOR(CHANNEL_LENGHT - 1 DOWNTO 0); -- Modulated audio sample output
m_axis_tlast : OUT STD_LOGIC; -- Channel indicator passthrough
m_axis_tready : IN STD_LOGIC -- Downstream ready signal
);
END ENTITY LFO;
ARCHITECTURE Behavioral OF LFO IS
CONSTANT LFO_COUNTER_BASE_PERIOD_US : INTEGER := 1000; -- 1ms
CONSTANT ADJUSTMENT_FACTOR : INTEGER := 90;
CONSTANT JSTK_CENTER_VALUE : INTEGER := 2 ** (JOYSTICK_LENGHT - 1); -- 512 for 10 bits
CONSTANT LFO_COUNTER_BASE_CLK_CYCLES : INTEGER := LFO_COUNTER_BASE_PERIOD_US * 1000 / CLK_PERIOD_NS; -- 1ms = 100_000 clk cycles
CONSTANT LFO_CLK_CYCLES_MIN : INTEGER := LFO_COUNTER_BASE_CLK_CYCLES - ADJUSTMENT_FACTOR * (2 ** (JOYSTICK_LENGHT - 1)); -- 53_920 clk cycles
CONSTANT LFO_CLK_CYCLES_MAX : INTEGER := LFO_COUNTER_BASE_CLK_CYCLES + ADJUSTMENT_FACTOR * (2 ** (JOYSTICK_LENGHT - 1) - 1); -- 145_990 clk cycles
-- LFO timing configuration constants
CONSTANT LFO_COUNTER_BASE_PERIOD_US : INTEGER := 1000; -- Base period: 1ms (1kHz base frequency)
CONSTANT ADJUSTMENT_FACTOR : INTEGER := 90; -- Frequency adjustment sensitivity (clock cycles per joystick unit)
CONSTANT JSTK_CENTER_VALUE : INTEGER := 2 ** (JOYSTICK_LENGHT - 1); -- Joystick center position (512 for 10-bit)
-- Calculate base clock cycles for 1ms period at current clock frequency
CONSTANT LFO_COUNTER_BASE_CLK_CYCLES : INTEGER := LFO_COUNTER_BASE_PERIOD_US * 1000 / CLK_PERIOD_NS; -- 1ms = 100,000 clk cycles
-- Calculate frequency range limits based on joystick range
CONSTANT LFO_CLK_CYCLES_MIN : INTEGER := LFO_COUNTER_BASE_CLK_CYCLES - ADJUSTMENT_FACTOR * (2 ** (JOYSTICK_LENGHT - 1)); -- 53,920 clk cycles (faster)
CONSTANT LFO_CLK_CYCLES_MAX : INTEGER := LFO_COUNTER_BASE_CLK_CYCLES + ADJUSTMENT_FACTOR * (2 ** (JOYSTICK_LENGHT - 1) - 1); -- 145,990 clk cycles (slower)
-- LFO timing control signals
SIGNAL step_clk_cycles_delta : INTEGER RANGE - 2 ** (JOYSTICK_LENGHT - 1) * ADJUSTMENT_FACTOR TO (2 ** (JOYSTICK_LENGHT - 1) - 1) * ADJUSTMENT_FACTOR := 0;
SIGNAL step_clk_cycles : INTEGER RANGE LFO_CLK_CYCLES_MIN TO LFO_CLK_CYCLES_MAX := LFO_COUNTER_BASE_CLK_CYCLES;
SIGNAL step_counter : NATURAL RANGE 0 TO LFO_CLK_CYCLES_MAX := 0;
SIGNAL tri_counter : SIGNED(TRIANGULAR_COUNTER_LENGHT DOWNTO 0) := (OTHERS => '0');
SIGNAL direction_up : STD_LOGIC := '1';
SIGNAL trigger : STD_LOGIC := '0';
-- Triangular wave generation signals
-- Note: Using signed counter with extra bit to handle full range calculations
SIGNAL tri_counter : SIGNED(TRIANGULAR_COUNTER_LENGHT DOWNTO 0) := (OTHERS => '0'); -- Triangular wave amplitude
SIGNAL direction_up : STD_LOGIC := '1'; -- Wave direction: '1' = ascending, '0' = descending
SIGNAL s_axis_tlast_reg : STD_LOGIC := '0';
-- AXI4-Stream control signals
SIGNAL trigger : STD_LOGIC := '0'; -- Trigger to indicate new processed data is ready
SIGNAL s_axis_tlast_reg : STD_LOGIC := '0'; -- Registered version of tlast for output synchronization
SIGNAL m_axis_tvalid_int : STD_LOGIC := '0'; -- Internal output valid signal
-- Audio processing signal with extended width for multiplication
-- Width accommodates: audio sample + triangular counter to prevent overflow
SIGNAL m_axis_tdata_temp : SIGNED(CHANNEL_LENGHT + TRIANGULAR_COUNTER_LENGHT DOWNTO 0) := (OTHERS => '0');
SIGNAL m_axis_tvalid_int : STD_LOGIC := '0';
BEGIN
-- Assigning the output signals
m_axis_tvalid <= m_axis_tvalid_int;
s_axis_tready <= (m_axis_tready OR NOT m_axis_tvalid_int) AND aresetn;
-- Output signal assignments with proper AXI4-Stream flow control
m_axis_tvalid <= m_axis_tvalid_int;
-- Input ready logic: Ready when downstream is ready OR no valid data pending, AND not in reset
s_axis_tready <= (m_axis_tready OR NOT m_axis_tvalid_int) AND aresetn;
-- Optimized single process for LFO step and triangular waveform generation
PROCESS (aclk)
-- Optimized single process for LFO timing and triangular waveform generation
-- This process handles both the frequency control and wave shape generation
triangular_wave_lfo_generator : PROCESS (aclk)
BEGIN
IF rising_edge(aclk) THEN
IF aresetn = '0' THEN
step_clk_cycles <= LFO_COUNTER_BASE_CLK_CYCLES;
step_counter <= 0;
tri_counter <= (OTHERS => '0');
direction_up <= '1';
-- Reset LFO generator to initial state
step_clk_cycles <= LFO_COUNTER_BASE_CLK_CYCLES; -- Set to base frequency
step_counter <= 0; -- Clear timing counter
tri_counter <= (OTHERS => '0'); -- Start triangular wave at zero
direction_up <= '1'; -- Start counting up
ELSE
-- Set the step_clk_cycles based on the joystick input
-- Calculate LFO period based on joystick input
-- Joystick mapping:
-- 0-511: Faster than base frequency (shorter period, higher frequency)
-- 512: Base frequency (1kHz)
-- 513-1023: Slower than base frequency (longer period, lower frequency)
step_clk_cycles_delta <= (to_integer(unsigned(lfo_period)) - JSTK_CENTER_VALUE) * ADJUSTMENT_FACTOR;
step_clk_cycles <= LFO_COUNTER_BASE_CLK_CYCLES - step_clk_cycles_delta;
-- Generate triangular wave when LFO is enabled
IF lfo_enable = '1' THEN
-- Clock divider: Update triangular wave at calculated rate
IF step_counter >= step_clk_cycles THEN
step_counter <= 0;
step_counter <= 0; -- Reset counter for next period
-- Check for triangular wave direction changes at extremes
-- Note: Using (2^n - 2) and 1 instead of (2^n - 1) and 0 to avoid edge cases
IF tri_counter = (2 ** TRIANGULAR_COUNTER_LENGHT) - 2 THEN
direction_up <= '0';
direction_up <= '0'; -- Switch to descending at near-maximum
ELSIF tri_counter = 1 THEN
direction_up <= '1';
direction_up <= '1'; -- Switch to ascending at near-minimum
END IF;
-- Update triangular wave value based on current direction
-- This creates the classic triangular waveform shape
IF direction_up = '1' THEN
tri_counter <= tri_counter + 1;
tri_counter <= tri_counter + 1; -- Ascending: increment
ELSE
tri_counter <= tri_counter - 1;
tri_counter <= tri_counter - 1; -- Descending: decrement
END IF;
ELSE
step_counter <= step_counter + 1;
step_counter <= step_counter + 1; -- Continue counting towards next update
END IF;
@@ -108,62 +137,73 @@ BEGIN
END IF;
END PROCESS;
END PROCESS triangular_wave_lfo_generator;
-- Handshake logic for the AXIS interface
AXIS: PROCESS (aclk)
-- AXI4-Stream handshake logic and audio processing
-- This process handles input/output data flow and applies the LFO modulation
AXIS : PROCESS (aclk)
BEGIN
IF rising_edge(aclk) THEN
IF aresetn = '0' THEN
s_axis_tlast_reg <= '0';
m_axis_tdata_temp <= (OTHERS => '0');
m_axis_tvalid_int <= '0';
m_axis_tlast <= '0';
-- Reset AXI4-Stream interface and audio processing
s_axis_tlast_reg <= '0'; -- Clear registered channel indicator
m_axis_tdata_temp <= (OTHERS => '0'); -- Clear temporary audio data
m_axis_tvalid_int <= '0'; -- No valid output data
m_axis_tlast <= '0'; -- Clear output channel indicator
ELSE
-- Clear valid flag when master interface is ready
-- Output handshake management:
-- Clear valid flag when downstream accepts data
IF m_axis_tready = '1' THEN
m_axis_tvalid_int <= '0';
END IF;
-- Data output logic
IF trigger = '1' AND (m_axis_tvalid_int = '0' OR m_axis_tready = '1') THEN
m_axis_tdata <= STD_LOGIC_VECTOR(
-- Data output logic: Send processed audio when trigger is active and output is available
IF trigger = '1' AND (m_axis_tvalid_int = '0' OR m_axis_tready = '1') THEN
-- Scale down the multiplication result to original audio bit width
-- Right shift by TRIANGULAR_COUNTER_LENGHT effectively divides by 2^TRIANGULAR_COUNTER_LENGHT
-- This maintains proper audio amplitude after modulation
m_axis_tdata <= STD_LOGIC_VECTOR(
resize(
shift_right(
m_axis_tdata_temp,
TRIANGULAR_COUNTER_LENGHT
m_axis_tdata_temp, -- Wide multiplication result
TRIANGULAR_COUNTER_LENGHT -- Scale factor
),
CHANNEL_LENGHT
CHANNEL_LENGHT -- Final audio sample width
)
);
m_axis_tlast <= s_axis_tlast_reg;
m_axis_tlast <= s_axis_tlast_reg; -- Output registered channel indicator
m_axis_tvalid_int <= '1';
trigger <= '0';
END IF;
m_axis_tvalid_int <= '1'; -- Mark output as valid
trigger <= '0'; -- Clear trigger - data has been output
END IF;
-- Data input logic
IF s_axis_tvalid = '1' AND (m_axis_tready = '1' OR m_axis_tvalid_int = '0') THEN
-- Data input logic: Process new audio samples when available and output is ready
IF s_axis_tvalid = '1' AND (m_axis_tready = '1' OR m_axis_tvalid_int = '0') THEN
IF lfo_enable = '1' THEN
-- Apply LFO tremolo effect: multiply audio sample by triangular wave
-- This creates amplitude modulation (tremolo effect)
m_axis_tdata_temp <= signed(s_axis_tdata) * tri_counter;
s_axis_tlast_reg <= s_axis_tlast;
s_axis_tlast_reg <= s_axis_tlast; -- Register channel indicator
ELSE
-- LFO disabled: pass audio through unchanged but maintain bit width
-- Left shift compensates for the right shift that occurs during output
-- This ensures unity gain when LFO is bypassed
m_axis_tdata_temp <= shift_left(
resize(
signed(s_axis_tdata),
m_axis_tdata_temp'length
signed(s_axis_tdata), -- Convert input to signed
m_axis_tdata_temp'length -- Extend to full processing width
),
TRIANGULAR_COUNTER_LENGHT
TRIANGULAR_COUNTER_LENGHT -- Compensate for output scaling
);
s_axis_tlast_reg <= s_axis_tlast;
s_axis_tlast_reg <= s_axis_tlast; -- Register channel indicator
END IF;
trigger <= '1';
trigger <= '1'; -- Set trigger to indicate new processed data is ready
END IF;
@@ -173,4 +213,16 @@ BEGIN
END PROCESS AXIS;
-- LFO Implementation Summary:
-- 1. Generates triangular wave at frequency controlled by joystick input
-- 2. When enabled: multiplies audio samples by triangular wave (tremolo effect)
-- 3. When disabled: passes audio through unchanged (bypass mode)
-- 4. Uses proper AXI4-Stream handshaking for real-time audio processing
--
-- Tremolo Effect Characteristics:
-- - Frequency range: Approximately 0.1Hz to 10Hz (typical for audio LFO)
-- - Modulation depth: Controlled by TRIANGULAR_COUNTER_LENGHT generic
-- - Waveform: Triangular (linear amplitude changes, smooth transitions)
-- - Bypass capability: Clean audio passthrough when disabled
END ARCHITECTURE Behavioral;