Electronics Introduction

  On the Arduino Uno , there isn't a dedicated LED that blinks specifically for   data transmission   (like serial communication). However, there is one that blinks for   data reception , and the confusion is very common. Let me clarify which LEDs do what: The LEDs on Arduino Uno 1. TX LED (Transmit) -  This is the main answer Location:  Labeled  "TX"  near digital pin 1 (D1) What it does:  This LED blinks when the Arduino Uno  transmits data  to the computer via USB serial. When you'll see it blink:  When your code uses  Serial.print()  or  Serial.println()  to send data to the Serial Monitor. 2. RX LED (Receive) Location:  Labeled  "RX"  near digital pin 0 (D0) What it does:  This LED blinks when the Arduino Uno  receives data  from the computer. When you'll see it blink:  When you send commands from the Serial Monitor to your Arduino . 3. Built-in LED (Pin 13) Location: ...

  We’ll design a   3-state machine   that controls an LED in different modes: OFF  → LED is off. SLOW_BLINK  → Toggles LED every  1 second . FAST_BLINK  → Toggles LED every  0.25 seconds . Hardware Setup CPLD Board : Xilinx CoolRunner-II ( XC2C256 ) or Lattice MachXO2 . Clock : Assume  12 MHz oscillator  (adjustable for timing). Inputs : A button ( btn ) to cycle through states. Outputs : One LED ( led ) for blinking. Step 1: VHDL Code for the State Machine vhdl library IEEE ; use IEEE . STD_LOGIC_1164 . ALL ; use IEEE . STD_LOGIC_UNSIGNED . ALL ; entity LED_Controller is Port ( clk : in STD_LOGIC ; -- 12 MHz clock btn : in STD_LOGIC ; -- Button to change state led : out STD_LOGIC -- Output LED ) ; end LED_Controller ; architecture Behavioral of LED_Controller is -- Define states type state_type is ( OFF , SLOW_BLINK , FAST_BLINK ) ; sign...