Embedded Systems Spring 2024
Lab 5 Traffic Light
Name: Mason Brady
Email: mrbrady1@fortlewis.edu

Traffic Light

Introduction: This lab was to learn how to do the full development work flow from problem to programmed FPGA
Materials GVIM, Vivado, Basys 3
Methods / Results:

1) 2 Way Traffic Light

I started by creating the truth table for the traffic lights. The trickiest part here was choosing the ideal 0 state which I think is when both are red this seemed to simplify my logic slightly better than the other variations I tried but their might be a better starting point. From this the logic expressions were pretty easy to find except for R2 because it has a nifty XNOR gate which was cool to see. It seems like theres a lot of right answers depending where you start but using this setup I didn't need a kmap since they were super easy and they only ones that required thought were the reds.

Figure 1. Hand Calculations for Logic Statements for Traffic Lights.

From this the code was fairly straightforward. Some of the parameters can be ignored for this part since I was just future proofing it for step two so I wouldn't have to rewrite anything (rh is the rushour enable). The code is fairly simple I think there is a better way of using the step count instead of breaking it up every loop but this worked out fine. Basically if the clock has reached the loop limit (2 for simulation and 50000000 for the Basys) then it increments the step in the loop and resets the timer. The step count is then used for the logic expressions above by just breaking it into it's individual bits and using the aformentioned logic. The simulation results are as expected. I found out that you can rearrange signals in the viewer which was nice to know especially for this project it made it much easier to read.

Figure 2. Simulation and HDL code for Two Way Traffic Light.

2) Rush hour
I didn't have to change much with my code for this to work just implemented the rush hour switch into a second if statement which looks for rush hour and state 100 and if these are true it uses a second timer maximum to double the time. Otherwise the code is identical

Figure 3. Rush Hour Modification

For the on board demonstration I only took one video demonstrating with and without the rush hour switch, it seemed silly to take and upload two videos of the exact same thing with one just slightly different. The video demonstrating both modes can be seen below



Discussion: This lab was great! This was the first time I have written HDL and it just worked. The only thing I had to debug for this entire lab was my timer being too short and not clicking program device and wondering why it wasn't working.