Power block

JuniorDesignProjectOScope

Teensy program to run oscilloscope and output to screen

Video Overview: https://www.youtube.com/watch?v=Kpc6_z2Lm2U&ab_channel=MarshallG

Showcase Page: https://eecs.engineering.oregonstate.edu/project-showcase/projects/?id=eiNZnlOKVvULkvkf

Design Problem: The design problem was to create a 2-channel oscilloscope. The scope needed to have voltage scaling, time scaling, and trigger capabilities. The system also needs to have AC/DC coupling modes, and a responsive interface.

Design process: The first step in our design process was to do some preliminary research to see what it was we would need to accomplish the requirements. This included taking into account the different choices of hardware we could use. We initially considered this project based on a field programmable gate array due to the high sampling requirement that were initially on the project instructions. After that requirement was removed, we went with our second option, which was a Teensy 4.0 microcontroller board. We went with this option because it is relatively inexpensive (especially compared to an FPGA), but it is still very fast with a clock speed of 600 megahertz.

Our next big hurdle was figuring out how to implement the input circuitry. Since we decided our input signal range was 0-20 volts peak to peak, and our microcontroller could only handle a range of 0-3.3 volts, we had to adjust the signal to be able to measure it. We worked together on designing the circuit and simulating the results in LTspice. We then soldered it to a protoboard and experimented with the circuit in the lab. Our team had to work together to troubleshoot the circuit and adjust the component values to perform as expected.

Although our whole system was split into individual blocks, we had to work together very closely to ensure our systems would work as expected. For example, the input conditioning block has to take voltage from the power supply block. Then the signal conversion and processing block had to take input from the signal conditioning block.Communication about these individual tasks made our system integration go smoother as the different pieces meshed together well.

Once all the circuit prototypes were designed and tested, we put them onto a PCB. We worked together to peer review the PCB to ensure it would work correctly. Once the board arrived, we used tools in the lab such as the oven and soldering irons to assemble the components onto the board. This phase was a challenge as we included some very small surface mount parts in our design. One challenge we had at this stage was that we had some slight mistakes in the PCB. The pin header where the microcontroller was supposed to be ended up being one pin too short. We fixed this by making an adapter board that mapped the pins of the MCU (expected one two that we didn’t need) to a set of pin headers that was the correct number for the footprint on the PCB.

We finished the process by working on our embedded software to control the device. This was a challenge because it included meshing together code covering many different tasks, all of which had challenges of their own.

Timeline: April 19th: Engineering requirments devised. April 26th: First block documentation. May 1st: First Block verification. May 10th: Second Block documentation May 15th: Second block verification. May 31st: System Verification. June 5th: Demo of final project.

Takeaways: Over the course of this project we learned about working on a complex project with a tight deadline. This taught us many lessons of project management and how to focus on prioritizing the important parts when it comes to developing electronics projects. Specifically we learned the importance of researching and simulation methods before diving into them. While this may seem restraining at first, it is a method that saves time and money in the long run because things are more likely to work the first time around. We also learned many things about specific technologies. Using direct memory access and interrupts to enhance the performance speed of our microcontroller were concepts that required us to research and access data that wasn’t as accessible as things we had worked on in the past.