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Lab 3: Audio Processing System #3

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PickleRick merged 43 commits from LAB3 into main 2025-06-07 22:18:48 +02:00
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LAB3/src/led_level_controller.vhd
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@@ -6,7 +6,6 @@ USE IEEE.MATH_REAL.ALL;
-- Entity: led_level_controller
-- Purpose: Audio level meter using LEDs to display real-time audio amplitude
-- Processes stereo audio samples and drives a bar graph LED display
-- Provides visual feedback of audio signal strength for both channels combined
ENTITY led_level_controller IS
GENERIC (
NUM_LEDS : POSITIVE := 16; -- Number of LEDs in the level meter display
@@ -33,8 +32,6 @@ END led_level_controller;
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 - 1;
-- Calculate the number of bits needed to represent the number of LEDs
@@ -50,17 +47,18 @@ ARCHITECTURE Behavioral OF led_level_controller IS
BEGIN
-- AXI4-Stream interface: Always ready to receive audio data
-- This ensures continuous audio processing without backpressure
-- Always ready for AXI4-Stream input
s_axis_tready <= '1';
-- Audio sample acquisition process based on channel identification
-- Processes incoming stereo audio samples and converts to absolute amplitude values
-- Uses s_axis_tlast to distinguish between left (1) and right (0) channels
-- Capture absolute value of input sample for left/right channel
PROCESS (aclk)
VARIABLE signed_sample : SIGNED(CHANNEL_LENGHT - 1 DOWNTO 0); -- Temporary variable for signed arithmetic
VARIABLE signed_sample : SIGNED(CHANNEL_LENGHT - 1 DOWNTO 0);
BEGIN
IF rising_edge(aclk) THEN
IF aresetn = '0' THEN
-- Reset: Clear both channel amplitude registers
abs_l <= (OTHERS => '0');
@@ -79,64 +77,72 @@ BEGIN
-- Right channel: Store absolute value of audio sample
abs_r <= UNSIGNED(ABS(signed_sample));
END IF;
END IF;
END IF;
END PROCESS;
-- LED refresh timing generator process
-- Creates a periodic tick signal to control LED update rate
-- Prevents LED flickering by limiting update frequency to human-visible rates
-- LED refresh tick generator
PROCESS (aclk)
BEGIN
IF rising_edge(aclk) THEN
IF aresetn = '0' THEN
-- Reset: Initialize counter and tick signal
refresh_counter <= 0;
refresh_tick <= '0';
ELSE
-- Normal operation: Count clock cycles and generate refresh tick
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
refresh_tick <= '1';
ELSE
-- Continue counting: Increment counter, no tick
refresh_counter <= refresh_counter + 1;
refresh_tick <= '0';
END IF;
END IF;
END IF;
END PROCESS;
-- LED level calculation and bar graph generation process
-- Combines left and right channel amplitudes and converts to LED display pattern
-- 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 2**NUMLEDS_BITS := 0; -- Calculated LED level for bar graph display
VARIABLE combined_amp : UNSIGNED(CHANNEL_LENGHT - 1 DOWNTO 0);
VARIABLE led_level : INTEGER RANGE 0 TO 2 ** NUMLEDS_BITS := 0;
BEGIN
IF rising_edge(aclk) THEN
IF aresetn = '0' THEN
-- Reset: Turn off all LEDs and reset level counter
led <= (OTHERS => '0');
ELSIF refresh_tick = '1' THEN
-- LED update cycle: Calculate new LED pattern based on audio amplitude
-- This section is executed once per refresh_tick to avoid flicker and ensure a stable display.
-- 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,
-- There isn't data loss 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)
-- The combined amplitude is mapped to the number of LEDs using a right shift.
-- 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.
-- Linear scale to LED level conversion to get the best visual effect
IF combined_amp = 0 THEN
led_level := 0; -- No audio signal, turn off all LEDs
ELSE
led_level := 1 + to_integer(shift_right(combined_amp, CHANNEL_LENGHT - NUMLEDS_BITS));
END IF;
-- Saturation protection: Limit LED level to maximum available LEDs
-- Prevents overflow and ensures the LED index stays within bounds.
@@ -144,16 +150,16 @@ BEGIN
led_level := NUM_LEDS;
END IF;
-- Generate bar graph LED pattern
-- Implements a "thermometer" style display: all LEDs from 0 up to (led_level-1) are ON.
-- All higher LEDs remain OFF.
-- The assignment first turns all LEDs OFF, then sets the lower 'led_level' LEDs ON.
-- Update LED output based on calculated level
led <= (OTHERS => '0');
IF led_level > 0 THEN
led(led_level - 1 DOWNTO 0) <= (OTHERS => '1');
END IF;
END IF;
END IF;
END PROCESS;
END Behavioral;