PCB Design Review: HDMI To LVDS Sony Vaio LCD Devboard

May 14, 2024 by 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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PCB Design Review: ESP32-S3 Round LCD Board

March 19, 2024 by 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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PCB Design Review: DPI-LVDS Sony Vaio LCD Devboard

March 12, 2024 by 11 Comments

Ordering a PCB with mistakes sucks. We should help each other avoid such mistakes – especially newcomers. One of the best ways to avoid these mistakes, especially if it’s your first one, is to get a few other people to look at it. You deserve to get a PCB that is as functional and as helpful as humanly possible, so that you can be happy with your project, and feel ever so slightly more confident in yourself in whatever you shall set out to do next.

At the end of last year, I put out a call for design review submissions, and we’ve received enough projects to make me feel overwhelmed for a bit. A design review has always felt like a personal thing, and here we are doing them in public. But in that sense, we hope that everyone can learn from them, and we hope to push forward a healthy review culture.

What’s more, these articles won’t just be design review. Every project I’m highlighting is worthy of a Hackaday feature just on its own, so tune in and learn more about them!

Today’s Contestant

For this example, I will be walking through a review I’ve already given someone with a pretty cool board, for a pretty cool project I’ve already shown you. Remember the Sony Vaio remake project? A fair bit of people have reached out to me afterwards, and one of them, [Exentio] also had the same Sony Vaio rebuild idea in mind. We started chatting, and he decided to tackle one of the project’s milestones, and perhaps the most crucial one – adapting the LCD.

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Oddball LCDs Reverse Engineered Thanks To Good Detective Work

December 12, 2023 by 5 Comments

Is there anything more discouraging to the reverse engineer than to see a black blob of epoxy applied directly to a PCB? We think not, because that formless shape provides no clue as to what chip lies beneath, and that means a lot of detective work if you’re going to figure out how to use this thing.

[Sudhir Chandra]’s detective story starts with a bunch of oddball LCDs, slim 1×32 character units rather than the more familiar 2×16 displays. Each bore the dreaded black COB blob on the back, as well as a handful of SMD components and not much else. Googling revealed no useful documentation, and the manufacturer wasn’t interested in fielding calls from a hobbyist. Reasoning that most manufacturers wouldn’t spin up a custom chip for every display, [Sudhir] assumed there was an ST7066, a common LCD driver chip, underneath the blob, especially given the arrangement of external components. But a jumper set was bodged together under this assumption didn’t get the display going.

Next up were more destructive methods, to decap the COB and see what kind of numbers might be on the chip. Sandpaper worked at first, but [Sudhir] eventually turned to the “Chips a la [Antoine]” method of decapping, which uses heat and brute force to get at the goods. This got down to the chip, but [Sudhir]’s microscope wasn’t up to the task of reading the die markings.

What eventually cracked the case was tracing out the voltages across the various external resistors and matching them up to other chips in the same family as the ST7066, plus the realization that the long, narrow epoxy blob probably covered a similarly shaped chip, which led to the culprit: an ST7070. This allowed [Sudhir] to build an adapter PCB for the displays, with plans for a custom Arduino library to talk to the displays.

This was a great piece of reverse engineering and a good detective story to boot. Hats off to [Sudhir] for sticking with it.

Adobe Scientist Cuts A Dash With LCD Shifting Dress

October 22, 2023 by 63 Comments

Adobe research scientist [Christine Dierk] showed off an interesting new project at the Adobe Max conference: Project Primrose, a dress covered with a series of liquid crystal panels that could react to movement, changing the design of the dress. Now, Adobe has released a paper showing some of the technical details of the process.

The paper is from the User Interface & Software (UIST) conference in 2022, so the examples it uses are older: it discusses a canvas and handbag. The dress uses the same technology, though, draped over a scientist rather than a frame. If you can’t access the version from UIST, [Dierk] has a free version here.

The dress uses Polymer-dispersed Liquid Crystal (PDLC) panels from the wonderfully named Shanghai HO HO Industry Co and is designed for use in windows and doors for privacy. It uses an Indium Tin oxide-coated PET film that is opaque by default but becomes transparent when a voltage difference is applied across the material.

These panels are shaped to a hexagonal shape, then wired together with flexible PCBs in a daisy chain. Interestingly, [Dierk] found that the smaller the panels were made, the lower the voltage was required to trigger them. For their canvas example, they dropped the voltage to a much safer -15V to 15V levels to trigger the two states, which is much safer for a wearable device.

The panels are also not completely transparent when triggered: the paper describes them as having a “soft ivory” look when they are overlaying a reflective material. Greyscales can also be made using Pulse Coded Modulation (PCM) to vary the panel’s transparency. Driving the panels at 3.2KHz, they created 64 shades of grey.

The main controller is a custom PCB with a Teensy 4.1 and a BlueFruit LE SPI module. The power comes from two 14.8V LiPo batteries, with converters to power the chips and switch modules so the Teensy can switch the -15 and +15V levels for the panels directly from each battery.

The array is made from modules, each with four panels connected to a controller PCB, which has several Analog Signal Device (ASD) ADG1414 chips. These receive the signals from the bus with switch registers to switch the panels individually.

Rather cleverly, [Dierk] uses the bus that daisy chains the modules together to deliver both power and the bus signal that controls the panels, using the -15 and +15V levels modulated with a 50Hz square wave to create the bus signal and power the panels at the same time. That’s a neat hack that reduces the complexity of the modules significantly.

The Teensy 4.1 controls the whole system and can use its IMU to sense movement and change the pattern accordingly. You don’t get to see the system’s electronics in the dress video, but they claim that the canvas example took just 0.58 Watts to drive, so the dress probably only needs a few watts.

It is a fascinating build (and a rather cute dress), and has a lot of potential. What would you do with this?

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Cheap LCD Uses USB Serial

September 11, 2023 by 19 Comments

Browsing the Asian marketplaces online is always an experience. Sometimes, you see things at ridiculously low prices. Other times, you see things and wonder who is buying them and why — a shrimp pillow? But sometimes, you see something that probably could have a more useful purpose than the proposed use case.

That’s the case with the glut of “smart displays” you can find at very low prices. Ostensibly, these are being sold as system monitors. A business-card-sized LCD hooks up via USB and shows your CPU speed, temperature, and so on. Of course, this requires sketchy Windows software. I don’t run Windows, and if I did, I wouldn’t be keen to put some strange service on just so I could see tiny displays of my system information. But a 3.5-inch IPS LCD screen for $15 or less probably has some other uses. But how to drive it? Turns out, it is easier than you think and the hardware looks reasonably hackable, too.

Like a lot of this cheap stuff, these screens are sold under a variety of names, and apparently, there are some subtle differences. Two of the main makers of these screens are Turing and XuanFang, although you rarely see those names in the online listings. As you might expect, though, someone has reverse-engineered the protocol, and there is Python software that will replace the stock Windows software the devices use. Even better, there is an example of using the library for your own purposes.

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Electronic Connect 4 Console Doesn’t Use LCD

May 28, 2023 by 9 Comments

You might think that making your own electronic games would require some kind of LCD, but lately, [Mirko Pavleski] has been making his using inexpensive 8X8 WS2812B LED panels. This lets even a modest microcontroller easily control a 64-pixel “screen.” In this case, [Mirko] uses an Arduino Nano, 3 switches, and a buzzer along with some 3D printed components to make a good-looking game. You can see it in action in the video below.

The WS2812B panels are easy to use since the devices have a simple protocol where you only talk to the first LED. You send pulses to determine each LED’s color. The first LED changes color and then starts repeating what you send to the next LED, which, of course, does the same thing. When you pause a bit, the array decides you are done, and the next train of pulses will start back at the first LED.

It looks like the project is based on a German project from [Bernd Albrecht], but our German isn’t up to snuff, and machine translation always leaves something to be desired. Another developer added a play against the computer mode. This is a simple program and would be easy to port to the microcontroller of your choice. [Mirko]’s execution of it looks like it could be a commercial product. If you made one as a gift, we bet no one would guess you built it yourself.

Of course, you could play a real robot. You could probably repurpose this hardware for many different games, too.

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