FPGA - LED Patterns

Lab #5 LED

Patterns

Due Date: 10/20/2020

For Lab #5, you will create a hardware component called LED_patterns that will create

light patterns using the LEDs on the DE10-Nano board. This component will run in the

FPGA fabric and you will create this component in VHDL. We will use this component

to control the LED patterns from software running on the ARM CPUs in a later lab, so

you can ignore the registers that are shown in the figure below for now. In the

upcoming lab you will instantiate the LED_patterns component in the

HPS_LED_patterns component where you will create the registers and control the LED

patterns from software. In this lab you will instantiate the component LED_patterns at

the top level in your Quartus project and the register related signals will be hardcoded

with appropriate values in the instantiation port map.

LED_patterns Entity

You will need to use the entity given below.

Entity Signals

Signal Description

clk System clock running at 50 MHz

reset System reset (typically tied to KEY 0)

PB Pushbutton signal that will be used to change state.

Tied to KEY 1.

SW The four switches that will be used to determine the next state.

HPS_LED_patterns Controls if the LED patterns are controlled from the hardware

state machine or from software via the LED_reg register. If set to

‘0’, which it will be for this lab, the hardware state machine

controls the LEDs. If set to ‘1’, The LED output signal is

connected directly to register signal LED_reg.

SYS_CLKs_sec Set to how many system clock periods are in one second.

Base_rate Set to control the base rate of LED transitions in seconds.

Note: This is an unsigned 8-bit fixed-point word with 4 fractional

bits. For example, if Base_rate = 1.0, then transitions occur

every 1 second.

LED_reg LED register signal for software control of LEDs

LED Output signal to drive the LEDs

Functional Description of LED_patterns

The overall function of the LED_patterns component is controlled by the

HPS_LED_control input signal. In pseudo code:

if (HPS_LED_control == 1) then

LED <= LED_reg (all 8 bits) // LEDs are controlled by software

else

LED <= controlled by hardware state machine.

LED Patterns State Machine

When in the hardware control mode (HPS_LED_control == 0), the following functionality

needs to be implemented:

1. LED7 always blinks at a 1 * Base_rate seconds regardless of what the state

machine is doing. This will allow you to verify that your base rate is set correctly.

2. The LED Patterns state machine has 5 states described in the table below. When

the state machine is in the noted state, you need to implement the following LED

patterns. Note that these run at different rates.

State Description

0 LEDs[6:0] show one lit LED shifting right at 1/2 * Base_rate seconds (circular

shifting) This is the default reset/powerup state.

1 LEDs[6:0] show two lit LEDs, side-by-side, shifting left at 1/4 * Base_rate

seconds (circular shifting)

2 LEDs[6:0] show the output of a 7-bit up counter running at 2 * Base_rate

seconds. (counter wraps)

3 LEDs[6:0] show the output of a 7-bit down counter running at 1/8 * Base_rate

seconds. (counter wraps)

4 User defined pattern. Implement your own pattern. It can’t be an up/down

counter or a right/left shifter or any pattern that you know of that any of your

classmates are implementing. Define your pattern and your pattern transition

rate, i.e. x * Base_rate seconds.

3. State Transitions. When the push button (PB) is pressed, the following sequence

needs to happen each time the push button is pressed:

3.1. The binary code of the switches is displayed on LEDs[6:0] for 1 second.

3.2. The next_state is determined by the binary code the switches represent. If the

switches specify a next_state of 5 or greater, the next_state is ignored and the

current state is kept (the switch code is display for 1 second though even if it is

5 or greater)

3.3. The next_state implements the functionality in the table above.

Conditioning the Pushbutton Signal

You need to create a component called PB_conditioner that does three things to the

input signal:

1. Synchronizes the signal (two D flip-flops)

2. Debounces the signal (ignore changes faster than 100 msec)

3. Creates a single pulse with a period of 1 system clock no matter how long the

pushbutton is pressed or how many times it bounces (small state machine).