Day: July 15, 2026

Making A Locked Down Wearable Work Without A Subscription

July 15, 2026 by 13 Comments

WHOOP does not have the presence in the wearable space as other brands, but in certain circles, it’s a household name. Their business model requires you to have a yearly app subscription to use their fitness tracker, but here at Hackaday, we are big fans of actually owning the devices you buy — which is why we were happy to hear about an open source and subscription free WHOOP compatible app!

The goal of the so-called OpenStrap project is not to re-create the WHOOP app. Rather, the algorithms and processing methods are developed from scratch, based on public research. It’s all calculated locally on a 1 Hz interval, based on the data the WHOOP 4.0 device feeds the app. As such, the health data collected from the watch, never leaves the phone. While not the main goal of the project, the privacy improvement of the app’s serverless nature cannot be overstated. However, to display metrics, you first need to get data off the WHOOP to begin with.

The crux of the issue with making the WHOOP 4.0 work without the official app is the reliance on proprietary Bluetooth protocols. Fortunately, the protocol itself ended up being relatively simple. The WHOOP 4.0 amounts to little more than a series of sensors that sit on the user’s wrist. As such, the app can subscribe to the Bluetooth feed and decode the data, right? Well, the devil is always in the details with such things, and the protocol came with its fair share of quirks. The hardware clock needs to be synchronized, or it simply defaults to zero Unix time. Moreover, the analog sensors like, ambient temperature are given in relative ADC values, and are not terribly useful without calibration. Regardless, the result of the reverse engineering effort speaks for itself with the OpenStrap app able to recreate much of the functionality in WHOOP’s official app.

Quite often, devices reliant on proprietary apps are little more than manufactured e-waste. While we don’t expect many of you to actually own a WHOOP 4.0, we do hope to see the OpenStrap project keep at least a few out of the landfill in the future.

Hacking Around The Financial Pain Of New 3DS XL Top Screens

July 15, 2026 by 10 Comments

With Nintendo’s 3DS experiencing a bit of a renaissance lately, prices for functioning systems have shot through the roof. Getting a busted one with a broken screen is a lot cheaper, but then you run into the eye-watering price difference between a replacement top screen for the regular version and the larger XL variant. The latter costs about the same as a whole new used 3DS, while the former goes for peanuts. Here the solution is obvious, with [Skawo] demonstrating how they hacked the cheaper, smaller top screen into a New 3DS XL.

The price difference on AliExpress as shown in the video is on the order of $120, with the smaller screen going for less than $10. Since they both use the same connector pin-out and display technology, you can plug either display into the New 3DS XL mainboard.

Where you’ll run into issues, other than the replacement display being obviously not XL, is the physically shorter flat flex cable for the controls that forces the display to be installed in an offset manner. You need jailbroken firmware like Luma3DS here to adjust for the screen offset. Filling in the missing screen real-estate is the other issue you have to patch over somehow, which was done here in barbaric fashion with some cardboard.

Beyond that it does work, and as a fix to at least get a broken New 3DS XL back into the game it’s worth considering. Do note that there’s a difference between regular 3DS and New 3DS (second generation) screens with neither being compatible, so be careful before you try such a fix.

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