PCB Design Review: HDMI To LVDS Sony Vaio LCD Devboard

May 14, 2024 by Arya Voronova 23 Comments

Today, we revisit another board from [Exentio] – a HDMI/DVI to LVDS transmitter for the Sony Vaio P display. This board is cool to review – it has a high-speed serial interface, a parallel interface, a healthy amount of power distribution that can be tricky to route, and many connectors to look over.

I’ve decided to show this review to you all because it demonstrates a PCB improvement concept we haven’t yet touched upon, that you should absolutely know about when doing board layout. Plus, I get a chance to talk about connector choice considerations!

The board is lovely. It integrates the DPI-LVDS circuit we’ve previously reviewed, but also a HDMI to parallel RGB chip from Texas Instruments, TFP401, a chip appreciated enough that even Adafruit has adapters with it. The fun thing about this chip is that it doesn’t even handle EDID like the usual HDMI to RGB/LVDS chips you get on cheap Aliexpress boards. So, there’s no firmware to take care of – it just receives a HDMI/DVI signal, converts it into parallel RGB, then converts that to LVDS, and off to the display it goes. The downside is that you have to provide your own EDID with an EEPROM, but that isn’t that tricky.

Again, this is a two-layer board, and, again, I like this – fitting tracks to the smallest possible space is a respectable and enjoyable challenge. This board has absolutely done well by this challenge. I do see how this board could be routed in an even better way, however, and it could be way way cleaner as a result. For a start, rotating the chip would improve the odds a whole lot.

The Chip Gets Rotated

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No Solder! Squeeze Your Parts To The PCB

May 11, 2024 by Elliot Williams 30 Comments

What’s solder for, anyway? It’s just the stuff that sticks the parts to the PCB. If you’re rapid prototyping, possibly with expensive components, and want to be able to remove chips from the board easily when you spin up the next iteration, it would be great if you didn’t have to de-solder them to move on. If only you could hold the parts without the solder…

That’s exactly the goal behind [Zeyu Yan] et al’s SolderlessPCB, which uses custom 3D printed plastic covers to do the holding. And it has the knock-on benefit of serving as a simple case.

In their paper, they document some clever topologies to make sure that the parts are held down firmly to the board, with the majority of the force coming from screws. We especially like the little hold-down wings for use with SMD capacitors or resistors, although we could absolutely see saving the technique exclusively for the more high value components to simplify design work on the 3DP frame. Still, with the ability to automatically generate 3D models of the board, parts included, this should be something that can be automated away.

The group is doing this with SLA 3D printing, and we imagine that the resolution is important. You could try it with an FDM printer, though. Let us know if you do!

This is the same research group that is responsible for the laser-cut sheet-PCB origami. There’s clearly some creative thinking going on over there.

Screenshot of the GitHub Marketplace action listing, describing the extension

Giving Your KiCad PCB Repository Pretty Pictures

May 4, 2024 by Arya Voronova 25 Comments

Publishing your boards on GitHub or GitLab is a must, and leads to wonderful outcomes in the hacker world. On their own, however, your board files might have the repo look a bit barren; having a picture or two in the README is the best. Making them yourself takes time – what if you could have it happen automatically? Enter kicad-render, a GitHub and GitLab integration for rendering your KiCad projects by [linalinn].

This integration makes your board pictures, top and bottom view, generated on every push into the repo – just embed two image links into your README.md. This integration is made possible thanks to the new option in KiCad 8’s kicad-cli – board image generation, and [linalinn]’s code makes KiCad run on GitHub/GitLab servers.

For even more bling, you can enable an option to generate a GIF that rotates your board, in the style of that one [arturo182] demo – in fact, this integration’s GIF code was borrowed from that script! Got a repository with many boards in one? There’s an option you could make work for yourself, too.

All you need to do is to follow a couple of simple steps; [linalinn] has documented both the GitHub and GitLab integration. We’ve recently talked about KiCad integrations in more detail, if you’re wondering what else your repository could be doing!

PCB Design Review: Tinysparrow, A Module For CAN Hacking Needs

April 3, 2024 by Arya Voronova 22 Comments

I enjoy seeing modules that can make designing other devices easier, and when I did a call for design reviews, [enp6s0] has submitted one such board to us. It’s a module called TinySparrow (GitHub), that helps you build your own vehicle ECUs and any other CAN-enabled things. With a microcontroller, plenty of GPIOs, a linear regulator and a CAN transceiver already onboard, this board has more than enough kick for anyone in hobbyist-range automotive space – and it’s surprisingly tiny!

You could build a lot of things around this module – a CAN bus analyzer or sniffer, a custom peripheral for car dashes, or even a full-blown ECU. You can even design any hardware for a robot or a piece of industrial technology that uses CAN for its backbone – we’ve all seen a few of those! It’s a great board, but it uses six layers. We’ll see if we can do something about that here.

Modules like TinySparrow will make your PCBs cheaper while ordering, too! Thanks to the carefully routed microcontroller and the CAN transmitter, whatever board you design around this chip definitely wouldn’t need six layers like this one does – and, unlike designing your own board, you can use someone’s well-tested and tailored libraries and reference circuits!

With TinySparrow, you save a lot of time, effort and money whenever you want to design a car or industrial accessory. After looking at the board files, my proposal for helping today’s board is – like last time – to make its production cheaper, so that more people can get this board into their hands if the creator ever does try and manufacture it. I also have some tips to make future improvements on this design easier, and make it more friendly for its userbase.

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Too Much Over-optimization Is Never Enough!

March 30, 2024 by Elliot Williams 21 Comments

A discussion came up on the Hackaday Discord PCB design channel about resistor networks, and it got me thinking about whether we (the hacker community) use them in designs or not. These handy devices often take the shape of an IC, SMD or otherwise, but between the pins are a bunch of resistors instead of active silicon. They come in all sorts of configurations and tolerances, but the point is usually the same: When you need a bunch of similar resistors, it’s cheaper to go with a network package.

But how much cheaper? I did a quick search for 1 kΩ resistors and the corresponding network, and came up with similar prices for the resistors and networks – but the network has eight resistors in it! That’s an eightfold savings! Which, at a price of roughly one cent per piece, is less than a dime. While it’s certainly true that if you’re making a million widgets, saving a penny per widget matters. But do you spend the time to optimize your projects down to such margins? I want to say “of course not!” but maybe you do?

For me, worrying about seven cents in a PCB design that I may make ten of is foolishness. But still, I’ve used resistor networks for their other side effects: the resistors in a common package tend to be very tightly matched, even if their overall tolerance isn’t. If you’re making something like an R-2R DAC, that’s a definite advantage. Or if you’re space constrained, or just hate placing lots of tiny resistors, the networks shine.

I often forget about resistor networks, and when I do think of them, I think of them in terms of cost savings in industrial applications. But maybe that’s not fair – maybe they do have their hacker uses as well. Are there other parts like this that we should all know about?

PCB Design Review: ESP32-S3 Round LCD Board

March 19, 2024 by Arya Voronova 6 Comments

For our next installment, I have a lovely and daring PCB submitted by one of our readers, [Vas]. This is an ESP32-S3 board that also has an onboard round TFT display, very similar to the one we used on the Vectorscope badge. The badge is self-sufficient – it has an ESP32, it has a display, a programming connector, two different QWIIC ports you could surely use as GPIOs – what’s not to love?

This is a two-layer board, and I have to admit that I seriously enjoy such designs. Managing to put a whole lot of things into two layers is quite cool in my book, and I have great fun doing so whenever I get the opportunity. There’s nothing wrong with taking up more layers than needed – in fact, if you’re concerned about emitted/received noise or you have high-speed interfaces, four-layer is the way to go. But making complex boards with two layers is a nice challenge, and, it does tend to make these boards cheaper to manufacture as a very nice bonus.

Let’s improve upon it, and support [Vas]’s design. From what I can see looking at this board, we can help [Vas] a lot with ease of assembly, perhaps even help save a hefty amount of money if they go for third-party PCBA instead of sitting down with a stencil – which you could do with this board pretty easily, since all of the components on it, save for the display, are the ones you’d expect JLCPCB to stock.

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Proper Routing Makes For Many Happy Return Paths

March 18, 2024 by Dan Maloney 18 Comments

Here’s a question for you: when your PCB has a ground plane layer, where do return signals flow? It seems like a trick question, but as [Kristof Mulier] explains, there’s more to return path routing (alternate link in case you run into a paywall) than just doing a copper pour and calling it a day.

Like so many other things in life, the answer to the above question is “it depends,” and as [Kristof] ably demonstrates in this concise article, the return path for a signal largely depends on its frequency. He begins by explaining current loop areas and how they factor into the tendency for a circuit to both emit and be susceptible to electromagnetic noise. The bigger the loop area, the worse things can get from a noise perspective. At low frequencies, return signals will tend to take the shortest possible path, which can result in large current loop areas if you’re not careful. At higher frequencies, though, signals will tend to follow the path of minimal energy instead, which generally ends up being similar to the signal trace, even if it has a huge ground plane to flow through.

Since high-frequency signals naturally follow a path through the ground plane that minimizes the current loop, that means the problem takes care of itself, right? It would, except that we have a habit of putting all kinds of gaps in the way, from ground plane vias to isolation slots. [Kristof] argues that this can result in return paths that wiggle around these features, increasing the current loop area to the point where problems creep in. His solution? Route all your signal return paths. Even if you know that the return traces are going to get incorporated into a pour, the act of intentionally routing them will help minimize the current loop area. It’s brilliantly counterintuitive.

This is the first time we’ve seen the topic of high-frequency return paths tackled. This succinct demonstration shows exactly how return path obstructions can cause unexpected results.

Thanks to [Marius Heier] for the tip.