Audio, Not Video Over The LKV373 HDMI Extender

August 2, 2023 by Matthew Carlson 11 Comments

[eta] found herself in a flat with several LKV373 HDMI extenders. Find the corresponding transmitter, plug it into your device, and you’ve got a connection to the TV/sound system, no fussing with wires behind the TV. However, [eta] wanted to get rid of the need to plug in a laptop and start sending packets directly to play music. As her flatmate [dan] had already reverse-engineered the receiver, she tested her prototype against their virtualized receiver, de-ip-hmdi.

The actual sending of images was surprisingly straightforward — just a JPEG sliced into 1024 bytes chunks and sent over. However, early testing showed nothing on the receiver. The end of a frame needed marking by setting the most-significant bit of the chunk number to one. Now de-ip-hdmi showed the image, but the actual hardware would not. With something missing, [eta] returned to Wireshark to scan packets. Noticing some strange packets on port 2067, she analyzed the pattern to reveal it sent another packet just before a new frame and included the frame number. With this tweak, it was still not enough. Ultimately, heartbeat packets sent every second synchronize things, but compared to the noise of the video packets, they were easy to miss. Now [eta] had some functioning video streaming rust code.

In theory, audio for the LKV373 followed the same thought process as video. Two channels of 32-bit big Endian integers at 44,100 hz chunked into 992-byte sections and sent as a packet formed the audio stream. With only 992 bytes, two streams, and 4 bytes per sample, each packet only held 2.812 milliseconds of sound. The first tests resulted in no audio output or distorted crunchy sound. Of course, this was every audio engineer’s worst nightmare: jitter. With a spin loop and an efficient ring buffer, the audio packets were soon slinging across the network reliably.

The code is available on a hosted version of GitLab. It’s a beautiful journey through reverse engineering some obscure but relatively cheap hardware. Along the way, there is nicely annotated Rust code, which makes it all the better.

Replacement Audi Plastics Thanks To 3D Printing

August 15, 2018 by Lewin Day 39 Comments

Old cars can be fun, and as long as you drive something that was once moderately popular, mechanical parts can be easy enough to come by. Things like filters, spark plugs, idle air solenoids – they’re generally available for decades after a car is out of production as long as you know where to look. However, plastics can be much harder to come by. 20 to 30 years into a car’s lifetime, and you’ll be hard pressed to find a radio surround or vent trim in as-new condition – they’ve all long ago succumbed to the sun and air like the cracked and discoloured piece in your own car. What is a hacker to do? Bust out the 3D printer, of course!

[Stephen Kraus] has developed a series of parts for his Audi, ready to print on the average home 3D printer. There’s the triple gauge mount which fits in the radio slot for that classic tuner look, to the printed wheel caps which are sure to come in handy after you’ve lost the originals. There are even useful parts for capping off the distributor if you’re switching to a more modern ignition setup. [Stephen] also reports that his replacement shifter bushing printed in PLA has lasted over a year in normal use.

This is an excellent example of what 3D printers do best – obscure, bespoke one-off parts with complex geometries are no trouble at all, and can be easily made at home. We’ve seen this done to great effect before, too – for example with this speedometer correction gear in an old truck.

Headlight Mod For An Audi A3

May 24, 2018 by Anool Mahidharia 24 Comments

If you have a car that is getting on in years, it may be missing some of the latest frills and features that the latest models sport. [Muris] has a slightly dated Audi A3 8P which did not have an AUTO setting for the headlights. In the newer models, this feature turns on the headlights when the ambient light falls below a threshold level (overcast conditions or when going through a tunnel), or when the windshield wipers are turned on. The light sensor is integrated behind the rear view mirror in a special mount, requiring an expensive windshield upgrade if he were to opt for the factory retrofit. Instead, he decided to build his own Automatic Headlights Sensor upgrade for his Audi A3.

His local regulations require the car headlights to be on all the time when the vehicle is in motion. So adding this feature may seem moot at first sight. But [Muris] programmed the headlights to be powered at 70% during daytime conditions and switch to 100% when his sensor detects low ambient light conditions. In the power save mode, all of the other non-essential lights (number plate, tail light) are also turned off to hopefully extend their life. He achieved this by using the VCDS (VAG-COM Diagnostic System) – a widely used aftermarket diagnostics tool for VW-Audi Group vehicles. His tiny circuit switches the lights between the two power settings.

His plan was to install the device without disturbing the original wiring or light switch assembly in any way. The low-powered device consists of a PIC micro-controller, an LDR (light dependent resistor) for light sensing and a low current relay which switches between the two modes. Setting the threshold at which the circuit switches the output is adjusted by a variable trimpot acting as a voltage divider with the LDR. [Muris] wired up a short custom harness which let him install this circuit between the default light switch and the car electronics. After switching on power, he has 15 seconds to enable or disable his unit by toggling the light switch five times, and that status gets stored in memory. The tiny board is assembled using SMD parts and is protected with a heatshrink sleeve. The circuit would work equally well with a lot of other cars, so If you’ve got one which could do with this feature upgrade, then [Muris] has the Eagle CAD files and code available for download on his blog.

Check out the video below where he runs a demo, describes his circuit in detail and then proceeds to assemble the PCB without using a vise or a third hand to hold the PCB. That’s a fancy watch he’s sporting at 00:50 s down the video.

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Audi Engineer Exposes Cheat Order

February 27, 2017 by Mike Szczys 88 Comments

In an interesting turn of events last week in a German court, evidence has materialized that engineers were ordered to cheat emissions testing when developing automotive parts.

Last Tuesday, Ulrich Weiß brought forward a document that alleges Audi Board of Director members were involved in ordering a cheat for diesel emissions. Weiß was the head of engine development for Audi, suspended in November of 2015 but continued to draw more than half a million dollars in salary before being fired ~~after~~ prior to last week’s court testimony.

Volkswagen Group is the parent company of Audi and this all seems to have happened while the VW diesel emissions testing scandal we’ve covered since 2015 was beginning to come to light. Weiß testified that he was asked to design a method of getting around strict emissions standards in Hong Kong even though Audi knew their diesel engines weren’t capable of doing so legitimately.

According to Weiß, he asked for a signed order. When he received that order he instructed his team to resist following it. We have not seen a copy of the letter, but the German tabloid newspaper Bild reports that the letter claims approval by four Audi board members and was signed by the head of powertrain development at the company.

Hackaday was unable to locate any other sources reporting on the letter other than the Bild article we have linked to (also the source used in the Forbes article above). Sources such as Die Welt reference only “internal papers”. If you know of other reporting on the topic please leave a comment about it below.

Vietnam War Helicopter Turned Amphibious Racecar

October 31, 2016 by Steven Dufresne 33 Comments

Our hats off to [SpeedyCop] and his [Gang of Outlaws] for turning a junked former Vietnam War helicopter into both an amphibious vehicle and a road race car. Yes, that’s right. It’s both driven on water and raced in the 24 Hours of LeMons at New Jersey Motorsports Park.

It started life as a 1969 Bell OH-58 Kiowa (US Army Vietnam Assault helo) and had not only served in Vietnam but also for a federal drug task force. It was chopped up for parts and the body found its way to [SpeedyCop] and friends. The body now sits on an 80s Toyota van chassis, has a Mazda Miata rear suspension, and Audi 3.0 V6 engine.

The pontoons were originally added to hide the seam between the helicopter body and the van but they then inspired the idea of making it amphibious. And with the addition of a four-blade, 7000 RPM propeller from a parasail boat, the idea became reality, as you can see in the video after the break (we suspect the trailing line is a rope to pull it back to shore in case of engine failure).

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Double Clutch Transmission Model

January 4, 2010 by Mike Szczys 44 Comments

[Alan] did an extraordinary job building a computer controlled model gearbox. His project from several years back is based on a dual-clutch Direct Shift Gearbox that was developed for VW and Audi vehicles. His design uses a gear head motor to provide the locomotion to this transmission. Shifting is computer controlled through serial cable, with servo motors providing the physical motion to change gears. Seeing all these moving parts in the clip after the break might make you a bit dizzy.

This is some extreme model building. It reminds us of the guy who built that aluminum aircraft model that was all over the Internets in December.

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