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

> 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 I eventually run out of both free time and executive function. AI's been helping... But I don't have the ability to tell when the output is wrong.

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interfeco 30 minutes ago | parent | next [-]

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 magnetics. This worked, but resulted in around 1% packet loss. When I moved it after the magnetics, I got 0% packet loss. This cost me a full revision, but I'd say this is the price to pay for not learning everything by the book.

	▲	15155 11 minutes ago \| parent [-]
		> 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

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qup 21 minutes ago | parent | prev [-]

Or, you could make some mistakes.

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mananaysiempre 5 hours ago | parent | prev | next [-]

> 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 not so easy.

Yeah, at first it feels stupid that every pretty LCD screen for bus or train stops, ads or whatnot has a full computer behind it, but then you ballpark the memory bandwidth and realize you need a ~ 1 GHz device anyway just to be able to chew through the pixels fast enough. (1920² px × 24 bpp × 60 Hz = 620 MB/s.) You also realize why “fill rate” used to be such a buzzword 20 years ago and why it took a while until true color became ubiquitous.

On the flip side of the O(n²), you can easily drive a watch-sized display with pretty good ppi using a 32-bit MCU, which is why the Apple/Google/Samsung battery-guzzling approach to smartwatches seems wrongheaded to me compared to Pebble/Zepp/etc.

	▲	markb139 4 hours ago \| parent \| next [-]
		Way back in time (1980s) I worked in the broadcast tv industry. We used to used digital still stores. A single frame of PAL took up 1MB of RAM. The machines had 2MB fitted. The board had a hardware cross fade function implemented in discrete logic chips. They also had a 20 or 40MB scsi drive. It was all controlled by a 6809 cpu. Quite impressive for the time
	▲	skippyfish 3 hours ago \| parent \| prev [-]
		Large displays are not driven by a general-purpose CPU that bit-bangs a single serial data line, and never were. They're driven by separate circuitry with direct memory access, often integrated on the die of chips meant for these applications. The actual bus to the display controller may be a parallel dot-clock RGB bus, or an ultra-speed differential multi-lane serial (MIPI DSI, HDMI, etc). And train stop displays certainly don't need 60 fps. The main constraint for high-resolution displays is memory, not CPU clock speed. Your (odd) 1920x1920x24bpp frame buffer takes up more than 10 MB.

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websap 8 minutes ago | parent | prev | next [-]

> I use AirPlay in my home exclusively, so I needed this streamer to support that

Doesn't Airplay switch you to other media on your device (e.g. Reddit, Youtube, etc) while browsing while streaming?

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interfeco 3 days ago | parent | prev | next [-]

Hey HN,

I've finally finished my dream music streamer featuring a vinyl-sleeve-sized square display, a custom carrier PCB for a compute module and a 3D printed case, running a custom-compiled kernel, Alpine mini rootfs and a small C app driving the display.

I did not think that this was doable by a hobbyist at all, let alone using free/open source software only (KiCAD, FreeCAD, VSCode). Turns out I was wrong!

	▲	dgellow 5 hours ago \| parent \| next [-]
		Congrats, that looks really neat :) Do you have plans to make the project open source?
	▲	yenepho 4 hours ago \| parent \| prev \| next [-]
		This is super cool! Thanks for sharing :)
	▲	oinoom 5 hours ago \| parent \| prev [-]
		very clean and well done!

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PcChip an hour ago | parent | prev | next [-]

Did you configure pipewire to allow multiple samplerates, so it can auto-switch the dac and not have to resample?

	▲	interfeco an hour ago \| parent [-]
		I am not using pipewire, just ALSA. AirPlay is (almost) always 44,100 Hz so there is not much to auto-switch to.

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reolbox an hour ago | parent | prev | next [-]

How did you learn PCB design? Any books or resources you can recommend? How long did it take you to learn?

	▲	interfeco an hour ago \| parent [-]
		Mostly YouTube and udemy courses. This one was pretty good in particular: https://www.udemy.com/course/high-speed-pcb-design-with-kica... I've spend around a month on the PCB as a hobby, next to a full time job.

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dsign 3 hours ago | parent | prev | next [-]

A bit tangential, and in the topic of nostalgia for old ways, remember when every block had a photo shop? Couldn’t we get a “PCB shop” in our bright near future? I wonder if the density of enthusiasts that need PCBs made is so low that the entire market is captured by only one or two companies based off China subject to the realities of shipping times.

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marcosdumay 2 hours ago | parent | next [-]

> I wonder if the density of enthusiasts that need PCBs made is so low that the entire market is captured by only one or two companies based off China

The sad answer is that yes, it is that low.

The better answer is that as PCB manufacturing gets more hands-off, we can look forward to some "PCB totem" somewhere in your city, like those self-service photo printers that exist now.

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greensoap an hour ago | parent | prev [-]

JCLPCB and who? Having a board made and assembled was both great in speed and effort, and terrible in cost markup when you add tarrifs on a $50 uc at 5 board minimum.

	▲	15155 8 minutes ago \| parent [-]
		China: PCBWay, NextPCB (hqpcb), ALLPCB, pcbx, PCBgogo North America: OSH Park Europe: AISLER

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rebolek an hour ago | parent | prev | next [-]

Oh, Absent Friends by Divine Comedy. What a beautiful record!

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kubb 3 hours ago | parent | prev [-]

> I was able build an out-of-band protocol extension into my audio player app

I wonder how that works.

	▲	interfeco 3 hours ago \| parent [-]
		Easier than it sounds: the app runs a simple http server that serves cover art by track id. The track id is transferred via iOS's built in "Now Playing" metadata fields, which is then used by the device to construct a query and fetch the full resolution image.