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attie, to random
@attie@chaos.social avatar

Schematics are a form of communication... So communicate!

There's nothing worse than a mystery box, with signals going in, and signals coming out... and no explanation.

Being forced to reach for the datasheet, when you're trying to understand a schematic is bad. Avoid it.

A screenshot showing the bridge IC itself, with the LVDS waveform and its slots. Each position is labelled with the associated output of the bridge IC.

karotte,
@karotte@chaos.social avatar

@jaseg @attie If you're lazy, pasting a screenshot of the PDF is also fine, I guess.

karotte, to random
@karotte@chaos.social avatar

Here's the project you all were wondering why it doesn't exist yet: https://digipres.club/@foone/111948980229300662, https://ioc.exchange/@azonenberg/110849751773610561

Introducing USBKVM! A keyboard, screen and mouse that all fit in your the palm of your hand!

It's built around the MS2109 HDMI to USB capture chip and its I²C interface connected to an STM32 MCU that takes care of the keyboard and mouse emulation.

While the hardware is fully functional, firmware and software are in a proof-of-concept stage. Stay tuned…

The raspberry pi desktop in a window titled "USBKVM". In the lsusb output in the terminal, there's a TinyUSB device.
ThinkPad UEFI setup startup page in the USBKVM window.

karotte,
@karotte@chaos.social avatar

Cleaned up the code, 3D-printed the case and wrote the readme.

Now it's ready for prime time: https://github.com/carrotIndustries/usbkvm

karotte,
@karotte@chaos.social avatar

USBKVM Pro, the follow-up with VGA update:

MS9288C eval board, aka really cheap VGA to HDMI converter box has arrived and works as advertised. Pinout appears to be similar, though not identical to the MS9288A, for which I found several sources.

What's strange is that none of the VGA pins needed for EDID or legacy ID are connected, yet two laptops detected it as monitor.

But how? Are the 75 Ohm RGB termination resistors sufficient for detection?

karotte,
@karotte@chaos.social avatar

@gsuberland These aren't connected either. The only pins connected are RGB, their respective grounds and HSync/VSync. They even were too cheap to connect the other two ground pins.

karotte,
@karotte@chaos.social avatar

USBKVM Pro board design is done, now waiting for the boards to arrive.

karotte,
@karotte@chaos.social avatar

Turns out, not all QFN-48s from the same manufacturer are created equal…

Anyhow, I wanted to know if everything's working before respinning the board, so I decided to play: will it bodge?

Yes! After spending two evenings soldering around 40 0.1mm magnet wires to the 0.4mm-spaced pads, I can confirm that the VGA input is working 😀

karotte,
@karotte@chaos.social avatar

@azonenberg Yeah, exactly.

Making a flex board wouldn't be really economical here. It's a small and cheap 4-layer board from JLCPCB.

karotte,
@karotte@chaos.social avatar

@azonenberg Oh, neat! Didn't know they were that cheap.

gsuberland, to random
@gsuberland@chaos.social avatar

heh, this 980Ti has one of those silly metal bus bar bridges for power delivery.

karotte,
@karotte@chaos.social avatar

@gsuberland At first glance this looked like a small lipo and I was really confused about its purpose…

Ninji, to random
@Ninji@wuffs.org avatar

Thinking about the new digital map I saw the other day, which managed to misspell the name of the area it’s in 👏

(Also, this font rendering looks very un-Windowsy; I wonder what the software is built on)

Closeup of the top right of the screen, which says “Patrick, March 17, 2024, 16:10”

karotte,
@karotte@chaos.social avatar

@Ninji Bad guess: Broken subpixel antialaising due to the portrait screen orientation.

gsuberland, to random
@gsuberland@chaos.social avatar

given all the complex requirements modern SoCs have for power rail sequencing, especially when DRAM is involved, I feel like vendors should put together some sort of standardised format for representing those sequencing requirements like they do with package pinout files. you could then have your EDA tool consume them by tying the data to specific nets in the design, figure out the intersection of requirements for shared rails, and enforce correctness via ERC rules.

karotte,
@karotte@chaos.social avatar

@whitequark @azonenberg @gsuberland

There's also the LTC2977. As to be expected for an ex-LT part its somewhat pricey. They have configurable thresholds and timing setting for pretty much everything and the software tool to configure them is really useful, but also somewhat on the janky side.

karotte,
@karotte@chaos.social avatar

@azonenberg @whitequark @gsuberland One can use as many as required by connecting their SHARE_CLK (and some other) pins in parallel.

karotte, to random
@karotte@chaos.social avatar

A couple of shitposts on my timeline about the link protocol used by TI calculators reminded me about an oddity of it that I haven't seen elsewhere:

It's a two-wire (red, white, GND) open-drain interface. One might assume, that one wire's clock and the other one is data or that one's RX and the other one is TX. However, it's none of that:

🧵 (1/2)

karotte,
@karotte@chaos.social avatar

To transmit a '1', the sender pulls the white line low, the receiver acknowledges this by pulling the red line low. The sender then releases the white line and the receiver finally releases the red line. For transmitting a '0', the sender starts with pulling the red wire low.

This has the nice property that it does bit-level handshaking and flow control and is self-clocking.

Despite these advantages, I've never seen such kind of protocol used anywhere else. If you have, let us know!

🧵 (2/2)

karotte, to random
@karotte@chaos.social avatar

So… I'm writing another piece of CAD software 🤓

Say hi to Dune 3D, a parametric 3D CAD that supports STEP import, chamfers and fillets!

It's the result of gluing together the UI from Horizon EDA with the solver from solvespace and Open CASCADE for a geometry kernel.

After about 3 months of off-and-on development, it's finally ready for prime time, go check it out on https://github.com/dune3d/dune3d#readme

Don't be surprised if it's a bit janky or lacks some features, there's still a lot left to be done…

karotte,
@karotte@chaos.social avatar

Packagers get ready!

I've prepared a preliminary release of Dune 3D for everyone to make sure that they'll be able to package the upcoming 1.0 release without any bad surprises: https://github.com/dune3d/dune3d/releases/tag/v0.9.3

There's also an MSI installer for all you Windows people out there: https://github.com/dune3d/dune3d/actions/runs/7577059606/artifacts/1179634166

If all goes well, the 1.0 release should happen next weekend.

gsuberland, to random
@gsuberland@chaos.social avatar

I was looking into Codec 2 for low bitrate telephony, and it turns out some researchers made their own decoder for it called Parametric WaveNet, which is a deep learning model that generates speech directly from the Codec 2 data stream.

listen to the Codec 2 samples, then the Parametric WaveNet samples. they're both the exact same encoder at 2400bps. the difference in quality and inteligibility is outstanding.

https://storage.googleapis.com/downloads.webmproject.org/icassp2018/index.html

karotte,
@karotte@chaos.social avatar

@gsuberland "Fun" fact: low-bitrate voice encoding shows up on multiple export control lists 😶‍🌫️

https://www.wassenaar.org/app/uploads/2019/consolidated/WA-LIST%20%2813%29%201.pdf

5.A.1.b.6: Employing functions of digital "signal processing" to provide 'voice
coding' output at rates of less than 2,400 bit/s.

On other lists, the limit is 700 bit/s.

Codec 2 even beats the 700 bit/s limit…

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