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Zhejia’s Status Report 3/11

This week, I worked on the interface between the magnetic charging and the seeed xiao BLE board. I researched the schematic diagrams and tested which pins can be used to charge the LIPO battery through the seeed board. We don’t want to directly charge the LIPO since the seeed board has a battery management system (BMS) already (BQ25100) which guarantees safe charging since overcharging LIPO batteries is dangerous. Looking through this schematic diagram, which is for the sense version of the board, but is the same ignoring the sense components, I found that charging is done though V_BUS, which is connected to the BMS, so the next step was trying to find an external pin that connected to V_BUS.  The pinout sheet given on the official website had it labeled as AD2 instead, so I spent some time trying to find which external pin was AD2 to no avail. Later, after examining the schematic again, I realized that this pinout sheet was for the nrf52840 chip instead of the seeed board. Although none of the pinout diagrams for the board officially labelled a pin as V_BUS, I presumed V_USB was likely connected to V_BUS since the USB was connected to V_BUS in the schematic. Then I used my power supply to provide 5V to the V_USB pin (pictures on the team status report), and at first it did not work, so I thought that V_USB might be connected to V_IN instead of V_USB, which would be an issue, but actually, the issue was connecting the ground pin to the ground terminal of the power supply did not work and it instead needed to be connected to the negative terminal of the power supply. In the end, I successfully charged the LIPO with 3.25V-5.5V although the 3.25V only provided 8mA of current while it basically gets full current of 60mA at 4.35V which matches the recommended operating conditions of V_USB in the datasheet. According to the datasheet, we also should be able to charge with low voltages using the VDD pin, but I have not tested that.

Of course, I worked on the design report as well.

My progress is on schedule, and I plan to research and start writing the keyboard driver software to send keypress data to the computer next week.

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Ben’s Status Report 3/11

This week I worked on implementing the connection between multiple Seeed BLE boards and a central controller. To facilitate this, I modified the peripheral code, having each Seeed board’s characteristic utilize the notify function to allow the central board to subscribe to multiple peripherals at once. Unfortunately, because I only brought 2 Seeed boards home, I had to buy a Arduino Nano 33 IoT to test the multi board connection. Luckily, the BLE library worked fine with the board and I was able to test the central connecting with two peripherals simultaneously. The code has been updated on the github to reflect these changes. I also wrote the Introduction, Use-Case requirements, Architecture, and Design Requirements sections of the design report and helped with the Design studies, Summary, and Glossary of Terms.

This work puts me a bit ahead of schedule since I believe this will allow me to scale up to multiple switch devices without much hassle.

Next week I plan to get multiple keys working and, when the single switch PCBs get here, solder together the switch breakout board with the Seeed boards and test their stability.

Here is a video of the two key receiver working: https://youtu.be/-SggOrEHb1I