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Team Status Report for 4/25/26

The most significant risk is the full integration of the FSR with the housing tip, and tuning the CPI in software, but these are being addressed with consistent testing and iteration. There were no significant changes made to the design, and our schedule is unchanged.

With our timing module tests, we found that our overall optical sensor to drawing latency is ~46ms, well within our 80ms requirement. Our CPI accuracy test yielded that a 45 degree tilt in sensor orientation from a horizontal orientation is within a 1% margin of error of the CPI with horizontal orientation. Our total weight, while not final yet, is ~40g, which is higher than our projected maximum of 30g, but this was a tradeoff for usability with more complex components. Measuring the current draw of our sensor combined with the MCU and battery resulted in an average active current draw of 23mA and an estimated battery life of 4.35hrs, well above our requirement of 2hrs.

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Christian’s Status Report for 4/25/26

This week I’ve mainly been working on getting the tip mechanics for the stylus printed out, and helping with physically integrating the components. I’ve had some hiccups in getting the tip sturdy and stable since it is the only moving component in our design, but I am making progress and should be done with the integration within the next two days. We are almost ready for the final demo!

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Christian’s Status Report for 4/18/26

This week I made more refinements to the 3D housing. After brainstorming with teammates, we decided to keep the front part of the housing solid while only sliding the back portion.  This allows us to place the FSR statically in the front and have a sliding mechanism for the tip of the pen to push on the FSR. I redesigned the tip of the pen to be a separate print from the body so that we can snap in the tip to the front, and have it slide back and forth with a hook mechanism to have natural presses of the FSR. I also had to make the housing thicker because of quality control reasons with how thin the 3D printer in TechSpark.

My progress is on schedule, and next week I hope to have everything integrated in the housing.

As I’ve designed the project, I had to learn how to 3D CAD in Fusion360 to make the housing and make sure the housing adheres to design constraints. In addition, I had to learn how to interface with the OS HID reports to take in external Bluetooth data.  I learned how to do these things through trial and error, and also online information.

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Christian’s Status Report for 4/4/26

This week I worked on beginning to physically integrate the force sensing resistor and optical sensor into the stylus housing. I extended the end of the stylus housing to include supports for mounting the optical sensor at an angle. For the FSR, I decided the optimal place for it is on the top of the USB-C port on the MCU. My progress is on schedule, and this next week, I plan to have a sliding-push tip mechanism in place for physically pressing the FSR.

For verification, since we have functionality for taking in data from the MCU and displaying writing on our canvas, I will work with Jamari to develop a testbench that measures the latency between when our data is received on the OS to when a line drawing appears on our canvas application. In addition, I will make a testbench that measures the amount of power draw from our lithium ion battery and gives an estimate of how much wireless writing time is left. For the 3D housing, I will weigh it with and without the internal components to verify it meets our requirements.

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Team Status Report for 3/28/26

The most significant risk right now is that we have to reorder our PCB for our optical sensor. Changes to the PCB are currently being made, and the risk is being managed by shifting our focus towards integrating our parts from the top down rather than bottom up from the sensor. This way, we can ensure our integration flow is working well and the sensor can be easily integrated once our new PCB is in.

No large scale changes have been made to the design of the system, just small scale optimizations and fixes.

Here is a picture of our current physical stylus with the MCU and battery integrated, and a screenshot of how writing on our canvas currently looks with using dummy data from the IMU rather than optical sensor data.

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Christian’s Status Report for 3/28/26

This week I worked on more iterations for our stylus housing, connected our battery to the MCU, and did the first testing of our conversion module with MCU data.

I did a lot more refining of the stylus housing this week to account our PCB wire placement, battery connection, and USB-C wire length. I created more  openings for wires and hollowed out the internals to make more room for the slack that the battery wire connection made.

Since we had some trouble with our sensor PCB, I’m using IMU data from the MCU as dummy dx/dy values, using the BLEHID Adafruit library to feed these values into the OS, and using these values in a largely unchanged conversion module.

My progress is on track, and for next week I hope to help with integrating the optical sensor into our data flow.

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Christian’s Status Report for 3/21/26

This week I did more refining on our stylus housing. I allocated a bit more room for the internal components since the fit was tight on the last iteration, and I also changed the tip shape to resemble more of a pencil shape. I also added a sliding latch on the back of the pen so that the two halves of the stylus can be held together better, and I extended the length to have a more comfortable hold. My goal right now is to make sure that all components fit well and the writing feels comfortable, then I will reduce the weight of the housing by hollowing out some of the material.

This week I focused more on iterating the housing since we’re still waiting on the optical sensor and pressure sensors to arrive. Both sensors should be in by early next week, so by the interim demo I will have basic functionality of the conversion module with the physical optical sensor and pressure sensor ready. I will take a step back from working on the housing when our sensors and PCB are in, since that is our most major delay.

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Team Status Report for 3/21/26

The most significant risk at the moment is the time needed to integrate and test all of our components when our sensor PCB gets in. The rest of our component functionality more or less depends on how well the optical sensor works, and we still need to receive and bring up the PCB. Once this is done though, we should be able to make significantly more progress in the next week and be ready for the interim demo. As stated before our contingency plan is that we have multiple components for our sensor and MCU, and should something not go as planned, we will at least have basic functionality by the interim demo, and time after that to address any issues.

No design changes or schedule updates have been made since last week.

Here are a couple iterations for our stylus housing and MCU fit that we are still iterating.

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Christian’s Status Report for 3/14/26

This week I made more edits to our housing design to account for the new size of our sensor PCB, and also experimented with code for integrating a pressure sensor into our design.

The idea behind the revised housing design is for our new sensor PCB to have a good field of view near the tip of the pen, while making the tip a lot narrower so that writing feels more natural.  This thinned out tip design is possible because our new optical sensor is a lot more compact that our initial one. This thinner tip also allows for our sensor to fully utilize its range of angle in the position it’s on our PCB.

I also worked a bit with code that replaces a button click for drawing with a pressure sensor threshold. As mentioned in our team report, we’re aiming to replace some of our button functionality with a pressure sensor, which will eliminate the need for a user to repeatedly press a button to draw versus move.

As mentioned before, progress is just a bit behind because of the waiting period for our sensor, but now that our PCB is getting in next week, I can expedite with lots of testing and tuning next week.

By next week, I will start integrating actual data from our MCU and sensor, since our physical PCB should be getting in by next week.

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Christian’s Status Report for 3/7/26

This week I worked more on iterating the 3D housing, as well as planning out testing for when we receive our sensor.

For the 3D housing, I allocated ~1mm of extra space for each component to account for manufacturing differences, and I rearranged the parts so that our MCU can be closer to the tip where users will likely hold the pen, so that our IMU can be more accurate. I also separated out the portion of the housing for the tip so that I can slim out the rest of the body, which will allow for a more comfortable writing experience. I also had to adjust the tip dimensions to account for our new optical sensor.

I haven’t made much progress with the conversion module since I already have the software side of it down as much as I can without having the sensor. Going further with tuning the conversion module has been bottlenecked by our troubles with getting a sensor, so when we actually do have it physically and integrated with our PCB, I can continue in tuning and testing the conversion module for the latency and CPI setting of our physical part. My progress is a bit behind because of this, but since we have our MCU’s in-hand now, I plan to send some “fake” CPI data from the MCU to try and better prime the conversion module for the real data when we get our sensor physically. This, in addition to cutting down in weight on our 3D housing by trimming excess plastic, is what I plan to get done in the next week.