Category: Status Reports

In the beginning of this week, I prepared for the final presentation and presented on Monday. Throughout the week, Amelia and I met to work on finalizing our integration between the RTL and the PCB. We were running into issues with our rotor settings (using the buttons and rotary encoder on the PCB). This took a lot of trial and error since it was hard to pinpoint what exactly was going wrong (the PCB itself, the individual modules, or their integration). We had made sure to test everything individually beforehand, so finally we realized the issue was the buttons on the PCB, since our implementation worked fine when we used the buttons on the DE-10 instead. We realized this was because we did not have any pull up or pull down resistors on the PCB. However, Amelia was able to work around this by having the buttons depressed while rotating the rotary encoder.

This upcoming week, we will finalize our poster, video, and report. I will also make sure we can demonstrate the RTL working on its own on the other DE-10 for demo purposes.

This week, Amelia & I worked on integrating our RTL with our many I/O components. On Monday, we fixed our issue with the rotary encoder skipping over values when going A-Z on our 7 segment display and then moved on to getting the rotary encoder to control the actual rotor settings, not just proxy 1-8 and A-Z variables. This led to some strange glitches that we then worked on debugging, which we still need to finish. On Wednesday, we worked on connecting the DE10’s GPIO pins to the PCB itself. This led to some strange issues, like some of the GPIO pins on the FPGA itself not working as expected, even when we just tested it with breadboard components. However, since Tanisha had gotten the PCB components soldered, we wanted to start working on the shift registers for the lampboard to make sure that worked as well. So, on Friday Amelia & I worked on getting the lampboard to work. We first started with a single shift register on a breadboard, and after some debugging, we got the lampboard to successfully display letters we input from the PS/2! This week, we will finalize our presentation and work on fully integrating, including working through the bugs with the 7 segment display and getting the lampboard to display the encoded data, not the PS/2 input data.

Over the course of this semester, I have learned a lot from this project. When selecting the right components, FPGA, and overall implementation, I had to read a lot of datasheets and documentation. While we’ve been introduced to this in classes before, it was definitely more daunting since there was less guidance, but overall it has made me more confident in my ability to evaluate the important information from these documents. Additionally, I had never worked with external I/O with an FPGA. This involved going beyond what I learned in 240/341. Similarly, we had to implement communication protocols at a lower level than using something like an Arduino library. This involved a lot of scrolling through the Internet on various forums and FPGA hobbyist blogs, as well as comparing Arduino library code to existing RTL implementations.

The past two weeks, Amelia and I have made good progress on the RTL. We currently have a working implementation of the rotary encoder, which can change the number displayed on the on-board 7 segment displays, but we do have some strange jumping issues when we try to implement it by scrolling through the alphabet, since there is some unexpected behavior on reset.  Additionally, we spent the majority of our time working on the external seven segment display that uses the MAX7219 chip. We had a lot of trial and error trying to adapt Arduino library code and existing RTL code (that was in VHDL, not Verilog) to work in Verilog. We used an Arduino to verify that the display itself worked, but after a lot of debugging, we successfully displayed a message early this week!

Later this week, Amelia and I worked on expanding our implementation of the variable rotor settings. For our demo, we only had users change the rotor starting setting (A-Z), but still hardcoded the rotor type (1-5) and ring starting setting (A-Z). On Friday, we spent most of the day implementing this and got all of the settings to display on the external 7 segment display! These settings could all be changed using the switches and buttons on the DE-10 and we verified that changing these settings reflected in accurate encryptions using an online Enigma simulator.

Now that the PCB has arrived, Amelia and I need to start wrapping up our RTL. This week, we will work on the shift registers for the lampboard, which should be pretty simple, and we will debug the rotary encoder implementation too. This will keep us on schedule.

As Amelia and I have been working on the RTL, it was very helpful to verify the individual components along the way. This made integrating them much easier. For example, we first got the rotor settings to display on the on-board DE-10. Using the on-board I/O (buttons and switches), we verified that the rotor settings could be changed and that they were correct when compared to the original Enigma machine using an online simulator. This included focusing on edge cases like the wrap-arounds from Z-A and the transitions at the knockpoints, which cause the other rotors to rotate as well. We also individually tested that the 7 segment display worked, and then incorporated that with displaying the actual settings. We will continue to run these targeted tests around edge cases and plan on conducting user testing to see how people who are not familiar with the design will interact with it. We want to ensure that the encryption is always 100% correct.

In the beginning of the week, Tanisha and I worked on routing the PCB, especially figuring out the routing around the shift registers and how best to organize the many LEDs/resistors to minimize trace complexity. Once she had finished the rest of the routing, we also worked to fix an issue with the 3.3V/GND pours on Fusion and I reviewed the layout one more time before Tanisha placed the order.

In the later half of the week, Amelia & I spent a lot of time in 1305 debugging the integration of the encryption modules with some basic GPIO using the buttons, switches, and 7-segment displays that already exist on the DE-10. This is a good stepping stone towards incorporating the GPIO from our PCB and also gives us a good way of demonstrating our progress in our interim demo.

More specifically, we initially had issues with the encryption itself being incorrect. One issue is that our 3rd rotor needed to be “rotated” once before encryption, so it was as if the first rotor started on Z when we expected it to be on A. While this was a quick fix, we also realized that we were overlooking the break code component of the PS/2 protocol. By incorporating an FSM that could alert our other modules of when a key was released (and therefore the break code was sent), we were able to fix our encryption and have the cryptographically correct result display when (and only when) the key was being held down on our external keyboard. This mimics how the lampboard will light up only when a key is pressed. Next, we moved onto incorporating more I/O. For the demonstration, we decided to make the starting rotor position for all 3 rotors variable, where switches would select which rotor to rotate and a button would allow you to cycle through the alphabet. After a day spent debugging this implementation, we successfully translated “Hello” to ciphertext and back on Saturday night! Here is a video of it working.

Next week, Amelia and I plan to work on capstone in the first half of the week before Carnival. We aim to incorporate the rotary encoder FSM that I wrote with our existing design and start on the I2C communication for the MAX 7-segment display. This will keep us on schedule since we want to have as little difficulties as possible incorporating the PCB by making sure the individual I/O components can work with our Verilog.