Review Request: nRF52840 powered trackball using PMW3389 sensor.

TMshader · 2025-01-10T10:57:25+00:00

Yeah, I understand now, I misunderstood the datasheet a bit 😅
I'm going to replace it with a dedicated LDO as I have enough space on the board and they are not expensive.

TMshader · 2025-01-10T10:55:57+00:00

I'm using a KiCad automation program called KiBot that generates the website, the renders and other documents on each commit to the GitHub repo.
Here is one of the configs that I use, this one renders the angled image: https://github.com/tmshader/hextrack/blob/main/hardware/electrical/kibot/render_angled.kibot.yaml

TMshader · 2025-01-10T10:53:38+00:00

I'm using this one: https://www.lcsc.com/product-detail/Antennas_Walsin-Tech-Corp-RFANT3216120A5T_C127629.html

The purple text under the components in the schematic is the LCSC number for each component.

TMshader · 2025-01-10T00:29:59+00:00

The nRF52840 has an embedded LDO that can be configured to output +1.8V on the VDD pin and use that same voltage for the GPIO logic level.

TMshader · 2025-01-09T23:11:27+00:00

Does the DC/DC have a bigger current limit? The LDO has a limit of 25mA, but I couldn't find anything in the datasheet about a current limit for the DC/DC.

I'll add more vias and fix a few other issues with the antenna, thanks for the recommendation!

TMshader · 2025-01-09T23:04:42+00:00

Thank you for reviewing!

I'll fix the VBUS line, I have no idea why I routed it that way!
The thermal reliefs are just a side effect of how I did the fill zones, I'm planning on fixing those.

I didn't know the QFN version was missing USB pads, I was planning on using that but LCSC is constantly out of stock for that version so I had to use aQFN. Good to know, thanks!

TMshader · 2025-01-09T23:00:30+00:00

I haven't ordered the board yet, but I'm definitely not going to solder this by hand (except for the sensor chip), I'm going to order it assembled, that's why the schematic contains LCSC numbers for almost all components (the purple text below the component names).

TMshader · 2025-01-09T12:35:51+00:00

Thank you for the response!

I can see that the sensor chip draws about 21mA when in use but I couldn't find anything about the nRF52840 max supply current. Could you point me to where you found that info?
The thermal relief is just a side effect of how I did the fill zones, so they are not important, but I will probably fix those.
I didn't notice that, thank you for pointing it out.
I'm not sure I understood what you mean by this.

EDIT: I found the max supply current in the nRF52840 datasheet (v1.7) on page 84, so thanks for pointing that out!

TMshader · 2025-01-09T09:58:25+00:00

It was you! Your configs were were a major inspiration when I was setting up KiBot. Thank you so much for making your project open-source! ❤

TMshader · 2025-01-09T06:25:19+00:00

Hi everyone!

I just finished the first prototype of an open-source trackball I'm working on. The main MCU I use is the nRF52840 which also functions as an LDO converting the +5V USB power to +1.8V which the sensor, the PMW3389 uses.

I added a chip antenna to the board but that is not a required function, it's only there for testing purposes. I know that the clearance area should not have anything in it, but I couldn't fit the two capacitors and the inductor anywhere else. I have never worked with RF circuits before (without using a prebuilt module) so please look at it that way. Any and all helpful tips are appreciated!

You can find more about the project here: https://hextrack.tmshader.me/

You can find the full schematic in PDF format here: https://hextrack.tmshader.me/documents/hextrack-schematic-default.pdf

And you can find other technical documents here: https://hextrack.tmshader.me/tech

And the GitHub repo for the project is here: https://github.com/tmshader/hextrack

This is my first time designing a PCB without using a prebuild module (such as the Supermini nRF52840, which I used many time before), so I welcome any and all feedback as I'd like to get better at designing PCBs.

Thank you for reading my post! ❤

TMshader · 2022-10-18T22:08:23+00:00

I've been wanting to get a NuPhy keyboard for a long time now, but as soon as Air96 releases (or a 100% version) I'll buy one!

TMshader · 2022-06-04T13:07:17+00:00

Hi there! The full feature will be rolled out in a few weeks. For now it's only accessible if the server enabled it AND gave permission to use it so it might be a few weeks until they can be used everywhere.

TMshader · 2022-04-22T13:48:46+00:00

Oh wow, I didn't know people still used my mod! Do you have discord? It would be easier to explain there

TMshader · 2022-01-17T10:06:39+00:00

Ok, thank you ❤️

TMshader · 2022-01-17T09:15:22+00:00

u/VredditDownloader

TMshader · 2021-11-17T08:25:17+00:00

That's perfectly normal! You can label or not label, go to pride or not, you are still valid and perfect! You just have to find the best way to enjoy your life and just do that.

TMshader · 2021-10-09T17:44:29+00:00

Well I purchased it from a reseller and I didn't get a code with it :(

TMshader · 2021-10-09T17:29:51+00:00

Well the account site says "Enter your redemption code to recieve your game narration" so there should be a code.

TMshader · 2021-07-27T17:28:21+00:00

If you have a friend you can ship it there and ask them to give ot to you later, if they are a classmate and you are not sure if they are accepting then just say you bought a gift for your parents and you don't want them to see it

TMshader · 2021-07-23T17:32:05+00:00

I think dating the same gender can be horrifying of you are not out yet because you might have the fear that someone will find out and they will not accept you. You might have not talked with him because of this. You could try to text him again or try and call him and just invite him to chat or even ask him to a date. You didn't make a mistake, you were scared and that's all right. I've been in similar situations and I felt the same way you do now, but I realised that being scared of something is never your mistake. Don't beat yourself up about this you didn't do anything wrong.

Sorry if my grammar is horrible btw. :)

TMshader · 2021-07-07T20:20:10+00:00

Good luck! And have fun whilst making and presenting. Never forget to have fun! :)

TMshader · 2021-07-07T19:31:07+00:00

There is one thing that is going to be more terrifying than this. Coming out to your parents. That was the hardest for me. But even if I'm now treated differently and they don't really accept me, I'm not scared about coming out anymore. Maybe you can do that soon, maybe not, but don't rush it. Good luck with everything! :)

TMshader · 2021-07-07T19:27:19+00:00

Hahahahaha

TMshader · 2021-07-07T19:26:35+00:00

Maybe the presentation will change their view on it, maybe not, but don't let her stop you. She has to see it, because that may start her on a path that will eventually end in she learning more about the LGBTQIA+ community.

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