LAB3/src/LFO.vhd

@@ -3,7 +3,7 @@ USE IEEE.STD_LOGIC_1164.ALL;
 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
+-- Purpose: Applies 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
@@ -106,7 +106,7 @@ BEGIN
                         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
+                        -- Note: Using (2^n - 2) and 1 instead of (2^n - 1) and 0 due to process signal assignment
                         IF tri_counter = (2 ** TRIANGULAR_COUNTER_LENGHT) - 2 THEN
                             direction_up <= '0';  -- Switch to descending at near-maximum
 
@@ -180,8 +180,8 @@ BEGIN
                 -- 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
+                        -- Apply LFO effect: multiply audio sample by triangular wave
-                        -- This creates amplitude modulation (tremolo effect)
+                        -- This creates amplitude modulation (effect)
                         m_axis_tdata_temp <= signed(s_axis_tdata) * tri_counter;
                         s_axis_tlast_reg <= s_axis_tlast;         -- Register channel indicator
 
@@ -212,11 +212,11 @@ BEGIN
 
     -- LFO Implementation Summary:
     -- 1. Generates triangular wave at frequency controlled by joystick input
-    -- 2. When enabled: multiplies audio samples by triangular wave (tremolo effect)
+    -- 2. When enabled: multiplies audio samples by triangular wave (multiplier value range from 0 to 1)
     -- 3. When disabled: passes audio through unchanged (bypass mode)
     -- 4. Uses proper AXI4-Stream handshaking for real-time audio processing
     --
-    -- Tremolo Effect Characteristics:
+    -- 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)

LAB3/src/all_pass_filter.vhd

@@ -4,7 +4,7 @@ USE ieee.numeric_std.ALL;
 
 -- Entity: all_pass_filter
 -- Purpose: A pass-through filter that maintains the same interface and timing
---          characteristics as a moving average filter but passes data unchanged.
+--          characteristics as the moving average filter but passes data unchanged.
 ENTITY all_pass_filter IS
     GENERIC (
         TDATA_WIDTH : POSITIVE := 24  -- Width of the data bus in bits
@@ -36,9 +36,9 @@ ARCHITECTURE Behavioral OF all_pass_filter IS
     -- Internal slave interface signals
     SIGNAL s_axis_tready_int : STD_LOGIC := '0';   -- Internal ready signal for input
     SIGNAL s_axis_tlast_reg : STD_LOGIC := '0';    -- Registered version of input tlast
+    SIGNAL s_axis_tdata_reg : STD_LOGIC_VECTOR(TDATA_WIDTH - 1 DOWNTO 0) := (OTHERS => '0'); -- Temporary storage for input data
     
     -- Internal data storage and master interface signals
-    SIGNAL m_axis_tdata_temp : STD_LOGIC_VECTOR(TDATA_WIDTH - 1 DOWNTO 0) := (OTHERS => '0'); -- Temporary storage for input data
     SIGNAL m_axis_tvalid_int : STD_LOGIC := '0';   -- Internal valid signal for output
 
 BEGIN
@@ -69,7 +69,7 @@ BEGIN
                 trigger <= '0';                       -- Clear data processing trigger
                 s_axis_tlast_reg <= '0';              -- Clear registered tlast
                 s_axis_tready_int <= '0';             -- Not ready to accept data during reset
-                m_axis_tdata_temp <= (OTHERS => '0'); -- Clear temporary data storage
+                s_axis_tdata_reg <= (OTHERS => '0');  -- Clear temporary data storage
                 m_axis_tvalid_int <= '0';             -- No valid data on output during reset
                 m_axis_tlast <= '0';                  -- Clear output tlast
 
@@ -88,7 +88,7 @@ BEGIN
                 -- (either no valid data pending OR downstream is ready)
                 IF trigger = '1' AND (m_axis_tvalid_int = '0' OR m_axis_tready = '1') THEN
                     -- Transfer stored data to output
-                    m_axis_tdata <= m_axis_tdata_temp;  -- Output the stored input data unchanged
+                    m_axis_tdata <= s_axis_tdata_reg;   -- Output the stored input data unchanged
                     m_axis_tlast <= s_axis_tlast_reg;   -- Output the registered tlast signal
                     
                     -- Set output control signals
@@ -101,7 +101,7 @@ BEGIN
                 IF s_axis_tvalid = '1' AND s_axis_tready_int = '1' THEN				
                     -- Store input signals for later output
                     s_axis_tlast_reg <= s_axis_tlast;   -- Register the tlast signal
-                    m_axis_tdata_temp <= s_axis_tdata;  -- Store input data (pass-through, no processing)
+                    s_axis_tdata_reg <= s_axis_tdata;   -- Store input data (pass-through, no processing)
                     
                     -- Set trigger to indicate data is ready for output
                     trigger <= '1';

LAB3/src/digilent_jstk2.vhd

@@ -44,7 +44,7 @@ ARCHITECTURE Behavioral OF digilent_jstk2 IS
 
     -- Calculate delay in clock cycles: (delay_period + 1_SPI_clock_period) * clock_frequency
     -- This ensures proper timing between SPI packets as required by JSTK2 datasheet
-    CONSTANT DELAY_CLK_CYCLES : INTEGER := (DELAY_US + 1_000_000 / SPI_SCLKFREQ) * (CLKFREQ / 1_000_000);
+    CONSTANT DELAY_CLK_CYCLES : INTEGER := (DELAY_US + 1_000_000 / SPI_SCLKFREQ) * (CLKFREQ / 1_000_000) - 1;
 
     -- State machine type definitions
     TYPE tx_state_type IS (DELAY, SEND_CMD, SEND_RED, SEND_GREEN, SEND_BLUE, SEND_DUMMY);
@@ -56,7 +56,7 @@ ARCHITECTURE Behavioral OF digilent_jstk2 IS
 
     -- Timing and data storage signals
     SIGNAL tx_delay_counter : INTEGER RANGE 0 TO DELAY_CLK_CYCLES := 0;  -- Counter for inter-packet delay timing
-    SIGNAL rx_cache : STD_LOGIC_VECTOR(7 DOWNTO 0);                      -- Temporary storage for multi-byte data reception
+    SIGNAL rx_cache : STD_LOGIC_VECTOR(s_axis_tdata'range);                      -- Temporary storage for multi-byte data reception
 
 BEGIN
 
@@ -80,7 +80,8 @@ BEGIN
         "01101001" WHEN SEND_DUMMY;         -- Dummy byte to complete 5-byte transaction
 
     -- TX State Machine: Sends LED color commands to JSTK2 module
-    -- Protocol: Command(1) + Red(1) + Green(1) + Blue(1) + Dummy(1) = 5 bytes total
+    -- Protocol: Command(1) + Red(1) + Green(1) + Blue(1) + Dummy(1) = 5 bytes total > Delay before next command
+    -- The delay is required by the JSTK datasheet to ensure proper timing between SPI transactions
     TX : PROCESS (aclk)
     BEGIN
         IF rising_edge(aclk) THEN

LAB3/src/effect_selector.vhd

@@ -28,7 +28,7 @@ END effect_selector;
 
 ARCHITECTURE Behavioral OF effect_selector IS
 
-    constant JOYSTICK_DEFAULT : STD_LOGIC_VECTOR(JOYSTICK_LENGHT - 1 DOWNTO 0) := STD_LOGIC_VECTOR(to_unsigned(2 ** (JOYSTICK_LENGHT - 1), JOYSTICK_LENGHT)); -- Default joystick value
+    constant JOYSTICK_DEFAULT : STD_LOGIC_VECTOR(JOYSTICK_LENGHT - 1 DOWNTO 0) := STD_LOGIC_VECTOR(to_unsigned(2 ** (JOYSTICK_LENGHT - 1), JOYSTICK_LENGHT)); -- Default joystick value (center position for 10-bit joystick is 512)
     
 BEGIN
 
@@ -52,9 +52,11 @@ BEGIN
                 -- X-axis behavior differs between modes
                 -- Note: When switching between modes, some outputs are reset while others preserved
                 IF effect = '1' THEN
-                    -- LFO Mode: Y-axis controls Low Frequency Oscillator period
+                    -- LFO Mode:
-                    -- Used for tremolo, vibrato, or other modulation effects
+                    -- Y-axis controls Low Frequency Oscillator period
+                    -- X-axis is ignored in this mode
                     lfo_period <= jstck_y;
+
                     -- Volume remains at last set value (preserved from previous mode)
 
                     -- Reset balance to center/default position when in LFO mode
@@ -64,9 +66,9 @@ BEGIN
                     -- Volume/Balance Mode:
                     -- Y-axis controls overall volume level
                     -- X-axis controls left/right audio balance
-                    -- Traditional audio mixer control mode
                     volume <= jstck_y;
                     balance <= jstck_x;
+
                     -- LFO period remains at last set value (preserved from previous LFO mode)
 
                 END IF;

LAB3/src/led_level_controller.vhd

@@ -1,6 +1,7 @@
 LIBRARY IEEE;
 USE IEEE.STD_LOGIC_1164.ALL;
 USE IEEE.NUMERIC_STD.ALL;
+USE IEEE.MATH_REAL.ALL;
 
 -- Entity: led_level_controller
 -- Purpose: Audio level meter using LEDs to display real-time audio amplitude
@@ -34,7 +35,10 @@ ARCHITECTURE Behavioral OF led_level_controller IS
     -- Calculate clock cycles needed for LED refresh timing
     -- Formula: (refresh_time_ms * 1_000_000 ns/ms) / clock_period_ns
     -- Example: (1ms * 1,000,000) / 10ns = 100,000 cycles for 1ms refresh at 100MHz
-    CONSTANT REFRESH_CYCLES : INTEGER := (refresh_time_ms * 1_000_000) / clock_period_ns;
+    CONSTANT REFRESH_CYCLES : INTEGER := (refresh_time_ms * 1_000_000) / clock_period_ns - 1;
+
+    -- Calculate the number of bits needed to represent the number of LEDs
+    CONSTANT NUMLEDS_BITS :  INTEGER := INTEGER(ceil(log2(real(NUM_LEDS))));
 
     -- LED refresh timing control signals
     SIGNAL refresh_counter : INTEGER RANGE 0 TO REFRESH_CYCLES := 0; -- Counts clock cycles between LED updates
@@ -91,7 +95,7 @@ BEGIN
                 refresh_tick <= '0';
             ELSE
                 -- Normal operation: Count clock cycles and generate refresh tick
-                IF refresh_counter = REFRESH_CYCLES - 1 THEN
+                IF refresh_counter = REFRESH_CYCLES THEN
                     -- End of refresh period: Reset counter and generate tick pulse
                     refresh_counter <= 0;
                     refresh_tick <= '1'; -- Single clock cycle pulse for LED update
@@ -109,7 +113,7 @@ BEGIN
     -- Updates only when refresh_tick is active to maintain stable visual display
     PROCESS (aclk)
         VARIABLE combined_amp : UNSIGNED(CHANNEL_LENGHT - 1 DOWNTO 0); -- Combined amplitude of both channels
-        VARIABLE led_level : INTEGER RANGE 0 TO NUM_LEDS := 0; -- Calculated LED level for bar graph display
+        VARIABLE led_level : INTEGER RANGE 0 TO 2**NUMLEDS_BITS := 0; -- Calculated LED level for bar graph display
     BEGIN
         IF rising_edge(aclk) THEN
             IF aresetn = '0' THEN
@@ -123,6 +127,8 @@ BEGIN
                 -- Combine left and right channel amplitudes
                 -- The sum of the absolute values of both channels gives a measure of total audio energy.
                 -- RESIZE ensures the sum fits within the variable's bit width.
+                -- There isn't data loss here since both abs_l and abs_r are one bit shorter than combined_amp,
+                -- due to the absolute value operation.
                 combined_amp := RESIZE(abs_l + abs_r, combined_amp'LENGTH);
 
                 -- Normalize combined amplitude to LED scale (0 to NUM_LEDS)
@@ -130,7 +136,7 @@ BEGIN
                 -- For 24-bit audio, shifting by (CHANNEL_LENGHT - 4) reduces the range to approximately 4 bits (0-15).
                 -- Adding 1 ensures that at least one LED lights up for any non-zero audio input.
                 -- Example: For 24-bit input, 1 + (combined_amp >> 20) gives a range from 1 to 16.
-                led_level := 1 + to_integer(shift_right(combined_amp, CHANNEL_LENGHT - 4));
+                led_level := 1 + to_integer(shift_right(combined_amp, CHANNEL_LENGHT - NUMLEDS_BITS));
 
                 -- Saturation protection: Limit LED level to maximum available LEDs
                 -- Prevents overflow and ensures the LED index stays within bounds.

LAB3/src/moving_average_filter.vhd

@@ -3,7 +3,7 @@ USE IEEE.STD_LOGIC_1164.ALL;
 USE ieee.numeric_std.ALL;
 
 -- Entity: moving_average_filter
--- Purpose: Implements a finite impulse response (FIR) low-pass filter using moving average
+-- Purpose: Implements a moving average filter for audio data
 --          Maintains separate circular buffers for left and right audio channels
 --          Filter order is configurable as 2^(FILTER_ORDER_POWER) samples
 ENTITY moving_average_filter IS

LAB3/src/volume_multiplier.vhd

@@ -58,7 +58,7 @@ BEGIN
 
     -- Volume to exponent conversion process
     -- Converts joystick y-axis position to bit-shift amount for exponential volume scaling
-    PROCESS (aclk)
+    VOLUME_CALC : PROCESS (aclk)
     BEGIN
 
         IF rising_edge(aclk) THEN
@@ -78,6 +78,7 @@ BEGIN
                 -- volume = 0-479:    Negative exponent (attenuation, right shift)
                 -- volume = 480-543:  Zero exponent (unity gain, dead zone)
                 -- volume = 544-1023: Positive exponent (amplification, left shift)
+                
                 volume_exp_mult <= to_integer(
                     shift_right(
                         signed('0' & volume) - to_signed(VOL_MID - DEAD_ZONE, volume'length + 1),
@@ -89,11 +90,11 @@ BEGIN
 
         END IF;
 
-    END PROCESS;
+    END PROCESS VOLUME_CALC;
 
     -- AXI4-Stream data processing
     -- Applies exponential volume scaling using bit-shifting multiplication
-    PROCESS (aclk)
+    AXIS : PROCESS (aclk)
     BEGIN
 
         IF rising_edge(aclk) THEN
@@ -155,7 +156,7 @@ BEGIN
 
         END IF;
 
-    END PROCESS;
+    END PROCESS AXIS;
 
     -- Example scaling factors (VOLUME_STEP_2 = 6, 64 values per step):
     -- volume_exp_mult = -3: Divide by 8 (>>3)

LAB3/src/volume_saturator.vhd

@@ -82,12 +82,10 @@ BEGIN
                     
                     IF signed(s_axis_tdata) > signed(HIGHER_BOUND_VEC) THEN
                         -- Positive overflow: Clip to maximum positive value
-                        -- This prevents "wraparound" distortion from mathematical overflow
                         m_axis_tdata <= HIGHER_BOUND_VEC;
 
                     ELSIF signed(s_axis_tdata) < signed(LOWER_BOUND_VEC) THEN
                         -- Negative overflow: Clip to maximum negative value
-                        -- This prevents "wraparound" distortion from mathematical underflow
                         m_axis_tdata <= LOWER_BOUND_VEC;
 
                     ELSE
@@ -109,11 +107,4 @@ BEGIN
 
     END PROCESS;
 
-    -- Saturation Purpose and Benefits:
-    -- 1. Prevents audio distortion from mathematical overflow
-    -- 2. Maintains audio dynamic range within valid bit representation
-    -- 3. Reduces wide multiplication results back to standard audio format
-    -- 4. Provides "soft limiting" behavior for volume control
-    -- 5. Ensures compatibility with downstream audio processing blocks
-
 END Behavioral;