Audi enthusiast upgrades 2001 A4 gear shift with old smartwatch in 3D-printed housing — vide-coded WearOS app displays gear selection, can be used to control in-car media

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Vibe coded WearOS app prevented the old smartwatch from becoming eWaste.

Smartwatch becomes gear stick crown
(Image credit: Desmontei on Reddit)

An electronics, automobile, and DIY enthusiast has turned an old smartwatch into an interactive gear shift display in his 2001 Audi A4 (B5) luxury compact executive car. The project started as just a bit of digital bling for the gear stick, but inspired by fellow Redditor comments, Desmontei vibe coded a WearOS app to add gear indicator and media control gestures to the repurposed digital dial. The watch face was secured to the gear stick very carefully, using a 3D-printed mount with tight tolerances.

Don't throw away old smartwatches! 3D printed a custom housing to turn one into a Digital Shift Knob. ♻️🕹️ from r/3Dprinting

The video shared in Desmontei’s Reddit post shows the smartwatch display changing to match the current gear stick selection. It appears to work as expected, but it wasn’t easy to ensure it reliably reported the correct gear selection. The watch’s accelerometer and gyroscope read the angle of the stick to work out what gear the car is in. However, the data can be thrown off when going uphill or downhill, so dynamic calibration had to be added to the algorithm.

Desmontei’s repurposed TicWatch Pro 3 also doubles as an intuitive media controller. When driving, you can change tracks in Spotify with back, forward, and pause swipes on the screen. The techy DIYer intends to add yet more functionality in due course. Specifically, ‘Phase 2’ will link it up “to an OBD2 scanner via Tasker for live telemetry (RPM, Temp).”

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For those who might wish to follow in Desmontei’s footsteps, there’s a lengthy (2 hrs) video to check out on the Desmontei YouTube channel. But, briefly, the DIYer “took an old TicWatch Pro 3 smartwatch and carefully cut the original casing with a rotary tool to extract just the OLED screen and motherboard. Then, I modeled a custom shift knob enclosure to house the electronics perfectly.”

The prototype’s tolerances had to be extremely tight “because I didn't want the screen popping out while shifting gears, and PLA was the easiest to test the fitment,” it is explained. If/when this prototype warps or breaks, “I'll use it as an excuse to reprint V2 in ABS or PETG,” Desmontei added. It’s a neat integrated solution, as the design bypasses the watch battery and is wired directly to the car’s 12V electrics.

Another change that may come in V2 could be the use of a second (reference) gyroscopic sensor in the car to make the gear shift position calculations more reliable. Desmontei's other exploits also include PlayStation and handheld modifications, as seen on their website.

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Mark Tyson
Mark Tyson
News Editor

Mark Tyson is a news editor at Tom's Hardware. He enjoys covering the full breadth of PC tech; from business and semiconductor design to products approaching the edge of reason.

18 Comments Comment from the forums
  • Jabberwocky79
    I'm a big proponent of avoiding E-waste when possible, although I don't have the chops to do this kind of stuff. My 2011-built PC is still serving as a backup, and I recently dismantled a 2012 iMac that had outlived its usefulness so I could rob the hard drive and turn it into a portable USB enclosure. I grabbed the memory while I was at it - Anyone have any use for 24GBs of DDR3 SoDIMM?
    Reply
  • usertests
    Jabberwocky79 said:
    I grabbed the memory while I was at it - Anyone have any use for 24GBs of DDR3 SoDIMM?
    I don't, but it's probably around $40-60 on the used market: https://www.ebay.com/itm/318255094455
    Reply
  • Notton
    Watch Audi/Porche add a digital screen shifter stick as an $1000 option.
    BMW will offer it as a subscription.
    Reply
  • salgado18
    The driver can find out which gear it's at just by touching the gear lever. I think it is a very nice trinket, but not much useful only for gear changes. However, it does open possibilites for other enhancements.
    Reply
  • Dementoss
    I've been driving for almost 34 years and, I've always driven cars with a manual transmission but, have never felt the need for a display on the gearknob, to tell me what gear I've selected...
    Reply
  • edzieba
    LOL. Instead of a bargain-basement BT OBDII module to read gearbox state directly and transmit to the display host, instead rely on IMU guesstimate which only works as long the the vehicle is never accelerating, braking, cornering, going up or down slopes, or encountering road camber.

    But what else do you expect from 'vibe coding'?
    Reply
  • cyrusfox
    edzieba said:
    LOL. Instead of a bargain-basement BT OBDII module to read gearbox state directly and transmit to the display host, instead rely on IMU guesstimate which only works as long the the vehicle is never accelerating, braking, cornering, going up or down slopes, or encountering road camber.

    But what else do you expect from 'vibe coding'?
    It wouldn't be terribly hard for it to base its state on a running average of position and use that, with optimized boundaries it would be more than good enough to know its current state.
    Reply
  • Jabberwocky79
    Dementoss said:
    I've been driving for almost 34 years and, I've always driven cars with a manual transmission but, have never felt the need for a display on the gearknob, to tell me what gear I've selected...
    Not everything has to be purely utilitarian. Sometimes people do stuff because it looks cool, not because it's needed.
    Reply
  • Pi2539
    This is brilliant! Great idea, looks create, and useful!
    Reply
  • edzieba
    cyrusfox said:
    It wouldn't be terribly hard for it to base its state on a running average of position and use that, with optimized boundaries it would be more than good enough to know its current state.
    The problem is, an IMU can't sense 'position'. It can sense orientation relative to local acceleration. Everything else is based on the assumption that that local acceleration is unchanging and equal to the local g-vector (i.e. gravitational acceleration whilst stationary). Once that assumption is broken - such as being placed in a vehicle that can be at different orientation and also accelerate in multiple directions (not just throttle & brake, but also centrifugal and centripetal) - you cannot infer from an IMU along which contributions to the measured orientation and accelerations are from the g-vector and which are from external influences.
    Reply