Adapter makes CarPlay connectivity wireless

Bluetooth and Wi-Fi combine to untether smartphone-to-car connections…at least until the former’s battery drains, that is.

At this year’s beginning, EDN published my overview and hands-on impressions of Apple’s CarPlay and Google’s Android Auto standards, which enable a vehicle radio or automotive head unit to be a display and controller for an iOS or Android device, respectively. Historically, both protocols leveraged a wired USB-based interface between mobile device and vehicle to accomplish the integration objective, for latency, bandwidth and interference-prevention reasons. Newer vehicle models switch to Bluetooth (for initial discovery and connection) and Wi-Fi (for ongoing transmission) communication, enhancing convenience. And bridging these two approaches are wireless adapters that mate an untethered phone to the tethered vehicle.

At the end of that prior coverage, I wrote, “FYI, I’ve also got two single-protocol wireless adapter candidates sitting in my teardown pile awaiting attention.”

Today I’ll analyze the insides of a CarPlay wireless adapter, albeit not the “unit from the Luckymore Store” that I initially planned on disassembling. Next month, I plan to take apart a wireless adapter that implements the Android Auto protocol. And I’ll subsequently wrap up my dissections with a dual-protocol wireless adapter functionally akin to the one still in use in my wife’s Land Rover.

Supplier disappearance and switcheroo

Here again is the wireless CarPlay adapter I’d originally intended as today’s patient.

Right now, as I write these words, it lists for $44.17 on Amazon’s website. But when I bought it in mid-December, it was on sale for $2.99 plus tax, with free shipping. Although the merchant subsequently reported to both Amazon and me that it had shipped, it never actually arrived. And I wasn’t the only one that had this same underwhelming seller experience. Yes, I got my $3.12 back eventually. 😀

I subsequently picked up this WOLIOS adapter (which apparently also came in white), well-reviewed but seemingly no longer available for sale as I write this, from Amazon’s Warehouse-now-Resale section for $11.85 in late February.

Gotta love these conceptual teardown images. And no, I don’t definitively know what “5G” means, either, although I suspect they’re referencing “5 GHz” Wi-Fi.

And, wrapping up the “stock content” suite, a promo video (which, alas, I can’t figure out how to embed) can be found here.

Overview introductions

Now for some real-life photos, as usual accompanied by a 0.75″ (19.1 mm) diameter U.S. penny for size comparison purposes, and of the product packaging first:

Next, what’s inside:

The red disc is an optional sticker for adhering the wireless adapter to the vehicle interior. The included USB-A (female) to USB-C (male) adapter for newer-vehicle use is a nice touch:

And now for our patient:

The hole in the center allows the status LED inside to shine through, as conceptually shown in the prior “stock” images. And the seam around the rim? I’m betting that’s our path inside.

Stubborn adhesive

Speaking of paths to the insides, let’s dive in.

Abundant exposure to my wife’s hair dryer on “high” (both temperature and fan speed) helped, but only a little. I resisted using my heat gun as it might have been melt-inducing overkill.

The last bit of the panel stubbornly refused to dismantle, so I eventually turned to a cutter tool.

Finally free, courtesy of a needle-nose pliers, albeit resulting in PCB mars.

This side’s much more interesting:

The embedded antenna at upper right is curious. As previously noted, two wireless broadcast links are necessary: 2.4 GHz Bluetooth for initial setup, and Wi-Fi for ongoing streaming. The latter is usually based on the 5 GHz band for higher transfer bandwidth, since range isn’t a concern in a diminutive vehicle interior. But I only see one antenna here.

Did the manufacturer figure out some way to passably enable it to support both bands? Or is there another one somewhere that I’m overlooking? Or does this particular design, in contrast to “Wireless Compability [sic]: 5.8 GHz Radio Frequency” spec claims to the contrary, leverage 2.4 GHz Wi-Fi instead? Or…???

Equally baffling is the user-inaccessible switch in the lower left corner (with the status LED to its right, in the middle of the lower edge). What’s the switch for? And then there’s the unmarked square IC enigma above and to the switch’s right (and LED’s left). I assume it’s the application processor, and that it runs at 24 MHz (courtesy of the marked oscillator to its left).

But who makes it, and what’s its specific product code? Another mystery. These are commonly Arm-based, with Chinese fabless suppliers Allwinner and Rockchip common sources (so says Google AI Overviews, at least), although this reverse-engineered unit from early and ongoing-leading adapter supplier Carlinkit reportedly leverages a Freescale (now NXP Semiconductors) SoC, the i.MX6 UltraLite.

To its right, and to the left of (and slightly below) the aforementioned antenna(e) assembly, is a Winbond W25Q128 128 Mbit serial flash memory, presumably housing the user-upgradeable system firmware image. And then there’s the even larger shiny-shield covered square IC below the antenna(e). This one’s easier to figure out, thanks to the careful application of a flat-head screwdriver acting as a lever.

It’s Realtek’s RTL8733, supporting the device’s wireless subsystem. The RTL8733 comprehends both Bluetooth and dual-band Wi-Fi transceiver functionality and presumably operates in conjunction with the mystery application processor to implement the adapter’s wireless-to-USB wired bridge functionality.

That’s all I’ve got for you today, folks. As always, let loose with your thoughts in the comments!

—Brian Dipert is the associate editor, as well as a contributing editor, at EDN.

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