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I learned PCB design, 3D printing and C just to listen to music

pentaton.app

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Re: I learned PCB design, 3D printing and C just to listen to music

#51
post #46

> Once I had the design [of the enclosure], I tried to 3D print it on my brand new 3D printer, which turned out to be a disaster. Took me some time to learn more about designing for manufacturing, especially for 3D printing. Would have been nice to hear how specifically it was made to work in the end. > Turns out, cross-fading two 4MP images at 60 frames per second on a moderately powerful single board computer is no…

As a mediatec guy I think the idea that everything needs to be 60 fps is a pest. I understand the idea in gaming, but it is not needed elsewhere. A train stop display can easily do its job at 1 fps or lower. You do not need to display motion at all and the 1 fps you need mostly for blinking things off and on (if there is no dedicated circuit for it). Most cinema films I watched projected from analog film looked perfe…

>Most cinema films I watched projected from analog film looked perfect at 24 fps

Until you get a panning shot and then it looks very juddery. Filmmakers have gotten quite good at dealing with the limitation but it is a limitation. (That said, you do have a challenge with higher fidelity video because it makes it harder to hide the imperfections in what the video is capturing, which makes things tend to look more fake)

Anime (and most animation) can adjust the framerate for what makes sense for the shot or even the element. It's common, for example, that panning happens on ones while the animation happens on twos or threes, because low-framerate panning looks bad and it's relatively easy with cell shading to animate the pan at a higher framerate. And again, the animators use a ton of techniques to deal with the low framerate and avoid the situations where it looks bad.

Which could also apply to train stop displays, if the graphics were designed for it (and almost certainly a consistent 24fps will look better than an inconsistent ~50-60fps).

Re: I learned PCB design, 3D printing and C just to listen to music

#52
post #51
post #46

Earlier quoted context omitted.

As a mediatec guy I think the idea that everything needs to be 60 fps is a pest. I understand the idea in gaming, but it is not needed elsewhere. A train stop display can easily do its job at 1 fps or lower. You do not need to display motion at all and the 1 fps you need mostly for blinking things off and on (if there is no dedicated circuit for it). Most cinema films I watched projected from analog film looked perfe…

>Most cinema films I watched projected from analog film looked perfect at 24 fps Until you get a panning shot and then it looks very juddery. Filmmakers have gotten quite good at dealing with the limitation but it is a limitation. (That said, you do have a challenge with higher fidelity video because it makes it harder to hide the imperfections in what the video is capturing, which makes things tend to look more fake…

Well I have worked as a camera operator. You can pan a tad bit slower or faster and this is a non-problem (and good camera operators know that and do that without even looking at the footage). The much more pressing limitation on cameras is typically the dynamic range between darkest and brightest color that can be captured.

Additionally a frame rate of 24 fps allows me to expose at 1/48 s, which means I get motion blur. That may seem like a bad thing, but for fictional stories I find a slight motion blur much more appealing and natural than exposing at 1/120 s for a 60 fps video or even at 100 fps with 1/200 s, which makes things look like a soccer television transmission. Of course in the age of digital you can get both by smearing frames into each other (depending on the camera), but the returns are IMO diminishing.

However I already mentioned I understand 60+ fps for certain applications (be it sports transmissions, gaming, films where it makes sense), but for a train station sign both the cited resolution and the frame rate are not strictly required. Sure. It is a nice to have if it comes for free, but rarely anything ever does.

Same goes for 4K. My students want to always do everything in 4K, yet most of them won't ever notice when a media player downscales their 4K footage to 1080p. 4K is cool if you have content that really makes use of it (e.g. hard one pixel lines) and a projection situation where the resolution can be noticed (e.g. audience very close to the screen), but that is the minority of situations.

Re: I learned PCB design, 3D printing and C just to listen to music

#53
post #46

> Once I had the design [of the enclosure], I tried to 3D print it on my brand new 3D printer, which turned out to be a disaster. Took me some time to learn more about designing for manufacturing, especially for 3D printing. Would have been nice to hear how specifically it was made to work in the end. > Turns out, cross-fading two 4MP images at 60 frames per second on a moderately powerful single board computer is no…

As a mediatec guy I think the idea that everything needs to be 60 fps is a pest. I understand the idea in gaming, but it is not needed elsewhere. A train stop display can easily do its job at 1 fps or lower. You do not need to display motion at all and the 1 fps you need mostly for blinking things off and on (if there is no dedicated circuit for it). Most cinema films I watched projected from analog film looked perfe…

I'm sure somebody has something to correct here, just my understanding of the 60fps in gaming thing:

a hold-over from 60Hz AC power, baked into NTSC television and inherited by arcades and early consoles as a structural default. Then it became a benchmark of sorts when the 3D era made 60fps harder to reach, and got exacerbated by early LCDs pretty much standardizing on 60Hz.

Then come games like COD (2007) with marketing for its 60fpsness, and the 2010s "cinematic 30fps" debaucle.

Personally, I'm fine with 45fps with butter smooth frametimes and no pop-in.

Edit: The semi-recent discourse of 'fake-frames' comes to mind aswell..

Re: I learned PCB design, 3D printing and C just to listen to music

#54

Earlier quoted context omitted.

Every variant comes up as not available. This is the listing, right? https://www.aliexpress.com/item/1005007516847708.html

Yes, this was it, looks like it is gone now. According to the CM3 datasheet [0] "Radxa CM3 will remain in production until at least Sep 2029", so there should be inventory hopefully. [0]: https://dl.radxa.com/cm3/docs/radxa_cm3_datasheet.pdf

I've been talking to them since before my first comment to you, and they are unable to sell even a single unit to a verified engineering team.

They told me that if I am willing to commit to at least 300 of the 4GB/32GB eMMC + BT/Wifi then they could produce them for me on demand.

I told them that it was insane to expect anyone to commit to developing a product around a platform that they would have to buy USD$30k worth of to see if it could (for example) support a particular display panel configuration using eDP.

Having this kind of chicken-and-egg problem is a quick way to doom a SoC, which is super frustrating because I definitely want to use it.

Re: I learned PCB design, 3D printing and C just to listen to music

#55

> I never did this before so there was plenty to learn, from basic electronics and magnetics to high-speed signal routing. How did you learn this? As a hobbyist I found hardware to be quite impenetrable, given the hard mathematics and physics requirements. My attempts to learn this essentially degenerate to taking an informal engineering course. It quickly becomes clear that I'm years away from making something, and…

> As a hobbyist I found hardware to be quite impenetrable, given the hard mathematics and physics requirements. IMO there aren't any. It's mostly about reading datasheets, and connecting pins to each other IOC those datasheets. Maybe the physics and mathematics are more important for analog electronics or designing ASICS? Do you have any specific projects you'd like to build? Post here and we can talk through it. And…

Sorry for the late reply.

> Do you have any specific projects you'd like to build? Post here and we can talk through it.

Sure thing. Yeah, I wanted to build a handheld cyberdeck, like these:

https://www.clockworkpi.com/uconsole

https://hackaday.com/2025/02/27/a-precisely-elegant-cyberdec...

https://hackaday.io/project/202522-cyberdeck-handheld

https://youtu.be/u8kYHgKKhjY

https://youtu.be/IB5OJr_MimQ

The truth is I use my phone a lot. I even write code on my phone, touch screen and all. It's limiting but I put up with it because the handheld form factor is too comfortable, I can use it from anywhere, even in bed.

The cyberdeck is meant to replace the phone with a real keyboard and x86_64 Linux computer, plus any useful peripherals I can cram into the thing. I wanted to use the LattePanda Mu, an Intel N100 System on Module.

I've actually downloaded KiCad and just started using it, figuring I just needed to get started and I'd figure it out as I went along. I just opened up the example schematics I downloaded and started connecting dots like a baby. I actually made some progress, even identified some issues with builtin KiCad libraries, like host/card PCIe socket mismatches that would lead to ERC failures, even tried to contribute those. Then I got severely intimidated when I realized I was trying to route PCIe lines, something even literal professional engineers on discord balked at. That killed the project for some time.

My second attempt came after I subscribed to Claude, who made me aware that the PCIe lines I was dealing with were third generation, and therefore "forgiving". Then I made more progress.

I managed to make some mockups and measure the exact comfortable typing range of my thumbs, and from that I derived an awesome keyboard layout. The keyboard prototype, the thing that will make or break the design, is already at the part where I need to spend real cash on it to have manufactured and shipped so I can test the switches. The taxes involved make it very expensive to make mistakes, though. It doubles the costs of everything.

So I switched to trying everything I can to make the entire system correct before I ship it. Finish the system as a whole and pay for a professional review of the entire thing before shipping even a single prototype. Asked Claude to help me design a safe power supply with BQ25792. Chose the screen for the deck, the same screen used by the Asus ROG Ally.

Wanted to design the full PCB too but I'm unsure if I should create a standalone keyboard first in order to test it out as a separate project. I feel like the whole project depends on it, but it doesn't make financial sense to prototype just that component.

Is there a way to ensure correctness before spending money on this hardware? I'd hate to spend money on this stuff, only to find it doesn't work. How can I reduce this risk?

Re: I learned PCB design, 3D printing and C just to listen to music

#56
post #23

Earlier quoted context omitted.

Just to be clear, I made a working prototype (and put a hyperbole in the title), I have a lot to learn still. You can learn something practical like "embedded DisplayPort should be impedance controlled to 100 Ohms" without fully understanding the physics behind it. AI can be very convincing. It told me to put the ESD protection as close the Ethernet connector as possible, so I put it between the port and the magnetic…

> so I put it between the port and the magnetics For GP: this is something you would learn from a PHY manufacturer's EVK schematics and layouts. TI (especially), NXP, Microchip show correct magnetics/ESD part numbers and placement - the trickier thing here is finding an EVK that doesn't just use an integrated MagJack. See https://www.ti.com/lit/df/snlr034/snlr034.pdf

Yeah I'm relying a lot on the TI datasheets for "known good" power supply schematics.

I chose an Intel N100 SoM and there's an example carrier board, but the whole point of my project is to customize that board. I wanted to do things like rewire the HSIO lines: turn the GPU PCIe socket into extra USB 3.0 ports and M.2 E sockets. The "known good" designs won't port over cleanly. It's PCIe gen3 over short runs, Claude tells me it's "forgiving" but I'm still nervous about it.

I'm placing an Intel I210-IT onto this board too, would definitely appreciate any tips!!

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