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Ben’s Status Report 2/18

https://youtube.com/shorts/qfVXAoujZhY?feature=share

This week, I got a single key to communicate via BLE to a controller. When the key was pressed, an LED on the switch and receiver will light up. I first started by finding an appropriate BLE library for arduino, which ended up being ArduinoBLE. From here, I defined a ledService for turning on and off the LED with a ByteCharacteristic to send the key press state. Debugging and troubleshooting took a lot of time because sometimes the device would fail to connect, but after a reset or a reflash, would work all of a sudden. This was solved after removing the serial initialization, when I realized that the device would lose power after being unplugged and before switching over to LIPO power, which caused the code to run again, which led it to continuously wait for a serial connection to the computer.

I believe my progress is on schedule, as I am scheduled to have a single key working this week. From what I gathered, I believe implementing multiple keys will not be too difficult.

Next week, I will try to implement multiple keys communicating with the central microcontroller, where each key module will be able to wireless transmit the pressed or unpressed state to the key.

18-220 was a great help to the progress this week, as it introduced me to the Arduino IDE and how to install various packages and program the correct board. Additionally, I applied my 18-349 experience of reading datasheets to determine pinouts and functionality (which is how I determined which pins to hook up the switch and the battery to). Additionally, Embedded taught me how to use minicom, which helped with debugging (since the Arduino IDE only lets you open a single serial terminal at once). Finally, the programming knowledge was learned during the last 2 weeks when I was researching the BLE protocol and how to implement it through arduino.

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Zhejia’s Status Report – 2/18

This week Korene and I troubleshooted our resonance issues from last week and found that the signal generators in the 220 Lab increased in voltage as the frequency increased, leading to being unable to spot the peak amplitude on the oscilloscope (the math->division menu item was also quite noisy). However, we moved to using the ADALM’s spectrum analyzer and found the resonance with no problem after setting that up.

After that, we also constructed the rectifier/receiver and transmitter circuits on breadboards and got it to output ~6V, which is the lowest charging voltage the Seeed Xiao microcontroller’s battery management system can take, but at too low of a current.

These are skills we learned in 18-220 and 18-100.

Here are some pictures and diagrams of our constructed circuits:

I also worked on the design PowerPoint slides with everyone else.

My progress is on schedule, and next week, I plan to try to increase the current delivered and try attaching the battery to microcontroller to a breadboarded circuit and get the microcontroller charging.

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Zhejia’s Status Report 2/11

I worked on the inductive charger, first making my own coil, then trying on some coils I acquired for more testing. I first calculated that the resonant frequency would be around 24 kHz, with the inductance of 43 microhenries in series with a capacitor of 1 microfarads. However, experimentally, I found that the real resonant frequency was very difficult to measure accurately as simply switching the direction of the probes would change the frequency at which I measured the highest output voltage for a given 5v input. Eventually, I settled on a ~41kHz resonant frequency for the inductor, which gave me an output voltage of ~3.4v (with a 5v input), which is close to the charging voltage for our planned small LIPO batteries, but I believe more investigation is required for the strange resonant measurement behavior.

We are mostly on schedule, having ordered/acquired the experimental parts needed, but the strange resonant behavior did put us a little behind schedule for proof of concept, which I will work on more with Korene next week to resolve. Asking staff may be an option as well.

In the next week, we will finish the proof of concept and create the circuit that integrates and stabilizes the magnetic charging for integration with the boards *when* they get here. (To be clear, the boards will likely not get here next week).

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Korene’s Status Reports 2/11

This week I had presented the proposal and rehearsed the speech in order to deliver in an engaging manner and also read through the application notes of several microcontrollers to see what will be the base microcontroller to use for our main pcb. In addition, Zhejia and I researched on inductive vs resonant charging and decided we best make an inductive charging station as that appears to have a more straightforward design. I found a test schematic for Zhejia to then test out to make a proof of concept.

We solidified our plan that the microcontroller be a USB-C that will plug into the computer with ease and that we can just have it run on BLE instead of having the conversion from BLE to Bluetooth, this can reduce latency and switching between too many protocols.

The magnetic charging will require the PCB so it’s debatable on whether we can use that for the hardware component of capstone and or I could focus more on optimizing the space for the key PCBs, I’ll consult with the TAs and faculty on whether this is a good idea. Either way using the NRF52832 will be useful as it’s a small microchip with great specs, speedy and small.

Next week I’ll research harder into how PCB layout works, as that is probably the subject that is of most concern for the keys.

Originally was thinking stacking the key PCB with the SEEED and the magnetic receiver pcb would be enough but I’ll look more into how the connection would work.

This week I did not get as much progress in depth research into the PCB making, but next week shall be full send.

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Team Status Report 2/11

We believe the most significant risks to the success of the project currently are the feasibility of wireless charging, the maximum number of devices possible through BLE, and the integration of all the components into the 22mm height permitted. For wireless charging, our backup plan is that the microcontrollers can pass through charge to the LIPO batteries via USB. For the BLE issue, we are managing the risk by looking into alternative BLE standards such as bluetooth mesh, with the backup plan to make some of the keys act as receivers pair multiple of the receivers with the central microcontroller. For the integration, we can use low profile cherry switches and cut down on some of the “nice to haves” such as hot swap capabilities to reduce the Z-height.

There have been no changes so far to the design of the system so far as we have not gotten enough parts in to experience any real integration challenges yet.

We have some pictures of a small inductive charger working posted in Zhejia’s status report.

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Ben’s Status Report for 2/11

This week I worked on ordering the parts and reading up on the BLE programming protocol for the Seeed XIAO nRF52840. I placed an order for 16 microcontrollers through the order form, which are on schedule to get here next week. Additionally, I did research on the BLE protocol and the role of devices in communication. I found that the microcontrollers would be best used in peripheral mode, with a specific GATT (Generalized Attribute) and service for each key. Each key should also only have notify and read permissions.

I believe that I am on schedule to begin programming the basic single key interface with the computer next week when the parts hopefully arrive. In the meantime, I will be continuing to work on the starter code so that once the board gets here, I can begin programming and debugging right away.

For next week, I hope to program a single microcontroller with the ability to determine whether or not a key is pressed and send that data over BLE.

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Zhejia’s Status Report for 2/4

This week, I worked on the website, specifically the introduction and wrangled with the formatting, and I worked on the proposal slides as well. We also spent significant amounts of time brainstorming over the recommendations and comments on our project idea and researching the feasibility of our project and solutions. For example, Korene and I did extensive research on the pros and cons of moving to a new project versus the validity of our use case, and solidified our justifications/explanations for our metrics, which we may not have explained well in the abstract. Additionally, we also researched various microcontrollers and compiled reasoning behind buying vs making our PCBs.

While a concrete weekly schedule has not been drafted for this week, we are on schedule with the pace of the course and ready for next week.

Next week, I hope to successfully implement resonance charging on a small scale to confirm the process and feasibility of wireless charging each key. We will need to work in the 220 lab and research the mechanism behind resonance charging, which is opposite to inductive charging.

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Ben’s Status Report for 2/4

This week I helped refine the project proposal and refine the use case. We initially thought about switching to a different project, but after some careful consideration, we decided to more clearly define the use case for our current idea. After careful consideration of multiple ideas, we decided to abandon our original I2C connected board and switch to BLE instead. I researched a variety of BLE capable microcontrollers, comparing factors such as size, ease of programmability, price, and availability to settle on the Seeed XIAO BLE. I also looked up the spec sheets of the switches we were planning to use (Cherry MX) and recorded key dimensions to aid in the search for parts. Finally, I tried to find similar projects online to see how we could improve on what’s already on the market, but there was not really anything similar.

My progress has been on schedule since I have made good progress or finished my tasks for the week. These included refining the project scope, performing an initial survey of possible electronic components we would need, and adding my contributions to the powerpoint.

Next week I hope to read up more on the BLE implementation on the Seeed XIAO BLE so I can be ready to program when the parts come in. Additionally, I hope to have the remainder of the parts decided and ideally ordered so we can begin prototyping as soon as possible.

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Korene’s Status Report for 2/4

What did you personally accomplish this week on the project?

This week I solidified with my teammates of our project idea and ensuring our project requirements and use case are valid in order to continue. Continuing forward I started researching how Bluetooth Low Energy works in regard to client and server connections. I completed my status report for the week, the team status report, and slides for the proposal

Is your progress on schedule or behind? If you are behind, what actions will be taken to catch up to the project schedule?

Progress is a bit behind in terms of researching BLE  I plan to do more research on how BLE works and also figure out what other footprints would be necessary for the PCB and if we need one. In terms of assignments, I am doing my part to be on track with assignments.

What deliverables do you hope to complete in the next week?

Completing a picture of logistics is crucial and having a draft of footprints and other parts needed in order to also determine how large our keys will end up being.