The Wand

Total time taken: 11 hr 40 min

5-26 00:00: Planning

It's planning day today! I want to research a litle and figure out the best way to do things. The design: have a mouse controlled entirely by accelerometers and gyroscopes. I'm aware it's worse than an optical mouse this way, but I would really like a way to write on something like excalidraw as if i was writing with an normal pen- so the mouse should be small enough to fit in my palm. The 3 main things that come to my mind today: the MCU, accelerometer/gyroscope, and battery. MCU should ideally support BLE because it's way nicer than having a wire coming out your palm (also my goal is to use this on a projector so I'd need a really long wire).

Small MCUs: the XIAO ESP32C3 (supports BLE!!), Tiny 2350, teensy (too big for my palm), QT Py

The xiao esp32c3 also has battery charging support so that's what I'm leaning towards.

For battery: again need something small; maybe this? it has decent charge for probably a few hours, and it's a small 3.5 x 3.5 cm square ish bat.

accelerometer + gyroscope: this looks cheap and good enough for what I need!

Time taken: 20 min

5-27 19:00: Wiring

Took a look at how everything should go together and came up with this wiring diagram:

seems fairly simple??

Time taken: 15 min

5-27 21:00: I forgot the buttons.

I don't want to use the buttons onboard the esp because I want to position them along the outside of the mouse, so they'll need to be a little flexible. Now I'm not 100% confident but I think the ESP should have internal pull ups, so I wont need resistors. 4 wires going to a single ground pin makes me a little uneasy though. Tomorrow I'll start designing the case, and hopefully in a few days I'll have written the code and finish the case.

Time taken: 15 min

5-28 09:00: Code

Decided to do the code first; Started simulating on wokwi: https://wokwi.com/projects/432109492341468161

Got the accelerator/gyroscope working and printing actual values, but I just realized the ESP32C3 doesn't support HID- stay tuned !!

Time taken: 30min

5-28 18:00: Code Part 2

Did a little more research and it seems like the ESP32S3 is really similar and does support HID- so that's what I'll be using instead. Replaced the MCU on wokwi. Noticed one thing though: the MPU6050 (similar to what I plan to use: the ST LSM6DS3TR-C) doesn't let you zero the sensor to a new position; I think it'll be more worthwhile to remove the calibrate button then. Removing the calibrate button, and adding a power switch because I forgot that the first time around;

Back to the code; I think I can use https://github.com/T-vK/ESP32-BLE-Mouse to act as the BLE mouse controller

wokwi needs you to pay to upload a library...we're going to continue blind then 🤩 I'll do as much as I can before adding mouse support then add that later.

Added some basic logic to handle angles, and added skeleton logic for mouse events!

Time taken: 1 hour

5-29 18:30: Code part 3

Okay I was approaching my code wrong- I was trying to take absolute positional degree/x/y/z movements, finding their speeds, then reapplying that to the mouse movement. ??? I realized I can pass the accel/gyro speeds to the mouse directly, so I rewrote the code to do that. Also realized I was moving mouse on gyro movementsi instead of accel. movements, so I fixed that by making the gyro the scroll and the accel. the mouse movements. I think that's pretty much done, I need to implement button presses now but that should be very simple- just reading the value of a button and calling mouse.press when it happens.

Time taken: 30 min

6-7 7:30 PM: Finishing the code, BOM

Finished the code! I added the button presses, and now it works as a mouse. Before I start designing the case, I need to figure out the BOM so I know what parts to design for. I know I'll be using the XIAO ESP32S3 and this battery, I just need to finalize the accelerometer/gyroscope and the exact buttons now. For the accelerometer i think I was thinking of something before, but I'll go with LSM6DSOX because it seems like it has very low noise - lower than the MPU6050. The code will change a little; Let me change that now

Ok, done and uploaded- mouse.ino

BOM time!! these soft buttons look nice, and I'll go with a typical rocker switch for the power. That should be all!

BOM: BOM.csv

while thinking of this ive now run into another problem: i need a 3 way splitter for the ground pin on the esp, but i can't find any

it's fine i'll just strip the wires and solder them together and make my own splitter

summary for today: writing more code, part sourcing, thinking 🥺 Time taken: 2 hrs

6-11 9:30 PM: More part sourcing, Start CAD

Ok, I did some more part sourcing to buy more things from mouser so its cheaper. I've added screws and wires to the BOM, I'll upload it soon. I think the only thing left is the elastic band i wanted to add. I've also started cadding: The design thought here is this:

3 layers; bottom is accelerometer screwed in for accuracy, and the two left/right buttons accessible from the bottom (easier to click while holding in the hand i think). Middle layer is the ESP; one of the walls will have a cutout for the XIAO's USB port so I can charge the device without needing to open the whole thing up. Third and final layer will be the battery. Still not sure how I'm going to design the lid, because I want it to be ome sort of snapfit so it's easy to open but I also don't really know how to design snap fits so uhh we'll see I guess. One of the walls will also have a cutout for the power switch.

Time Taken: 1.5 hrs

6-12 8:45 PM: CAD

I've started dropping the cad models for my actual components in so I can design around them. So far, I've rethought where Iw ant the buttons to be. I also think 3 layers will be too thick, so I'll sacrifice an extra 5mm width for a thinner device. The XIAO is laying next to the accelerometer, but I'm not sure how to secure it in especially since there are no mounting holes. here's where I'm at now:

Thought about it for a quick second and I'll put small walls around the xiao so it doesn't move hopefully that's enough 😭 I'm thinking of putting a screwable panel on top of both the boards anyways to separate the battery, so maybe that'll all hold the ESP in. Made a cutout for the usb port, and stuck my button in.

what's left: the other button, tolerances for the buttons, power switch, separation panel (?), battery (?), and lid. I think lid will be the hardest considering I have like no experience but we'll see.

Time taken: 2.5 hrs

6-13 11:00 PM: Rocker Switch

Spent a few min adding a cutout for the rocker switch...how in the world is it so big I need to rethink this, potentially findding a smaller rocker switch because this leaves like no space for the battery.

Time taken: 20 min

6-22 10:00 PM: Slideswitches

Okay back after a hiatus. looked into slideswitches instead of rockers; I think they'll work, but it's not worth it to have the rocker switch on this existing model. I want to extend the model a little bit, open it up a little, then make some space for the switch on the side.

mini update: I got the switch in, but I think my second button (for right clicking, etc.) might be too close

also just realizing the holes arent big enough for the buttons; i think i should be able to push the prongs in? I'm not sure whether thsi much interference warrants me opening the hole a little

I've adjusted the spacing there, I'm more comfortable with the gap now. If it still doesn't work out, I can bend the pins a little or push the buttons out further.

To do: add a little flat plate for the battery to sit on, check the battery in the case, add lid, clean up the case.

Time taken: 1hr

6-23 11:00 AM: Battery

Preliminary battery fitting:

I mean it fits alright, but the lead wires are an additional 25mm. The edge of the battery to the edge of the case is 12 mm. I'm thinking I'll loop the wire above the battery (so just let it sit on top of the battery) so it'll probably be okay? There seems to be enough space to maneuver the wires without crimping them. I'm afraid I'm not giving myself enough wiggle room here tho...

battery plate!!

To clarify, the main reason I want this plate between the battery and the rest of the components is bc I don't want anything to accidentally puncture/affect the battery- I'd like as much separation as possible.

To do: lid, polishes

Time taken: 45 min

6-24 10:00 AM: Lid + final touches

I've decided on a sliding lid. I just did a sliding lid on another one of my projects and it worked out quite well imo. The only thing is it'll add a little bit of height but it's ok.

made the rails (will filet the inside later):

lid!!!

time to polish

done !!

fileted it a bunch so it's comfortable to hold + added a nice little embossing.

To do: update BOM, write README, upload CAD source files

Time taken: 45 min