DIY: Wireless screen mirroring & audio/video streaming from iPhone/iPod/iPad to MMI
This topic will contain the steps I went through to get my iPhone screen mirrored to the MMI without plugging a cable into the phone. This also means that audio/video streaming is supported (e.g. starting a youtube video on the phone and then "casting" it to the MMI).
Prerequisite: your car must have the Audi Music Interface (AMI) option.
Main parts needed:
- Wireless router (optional: having a 4G-enabled router means you'll also get an internet hotspot in the car)
- Apple TV 3rd gen (4th gen is also possible to use and would have much more features as it has its own AppStore but I wasn't sure about the result when I started looking into this and didn't want to spend the extra money for it; i got the 3rd gen used for 70$)
- AMI to RCA cable
- HDMI to analog video converter
- HDMI-HDMI cable
No, let's break it down:
The wireless router: this has the main purpose of creating a WiFi network for both the phone and Apple TV to connect to, so they can talk to each other. My main idea was to skip the router and just have the Apple TV connect to the iPhone's hotspot but this turned out not to be a viable option because the iPhone itself is not connected to the WiFi network it creates.
An added bonus of this is that by using a 4G-enabled router (or, as I did, a router with a USB port into which a 4G stick can be inserted), the car will get its very own internet hotspot, which is kinda cool.
The router, the 4G USB stick and the cable I use to charge my phone while streaming from it (I'm keeping it in the armrest):
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The Apple TV: This needs a bit of work, because the Apple TV is normally meant to be powered from a wall socket (110V/220V AC) and we need to get it to run on DC at much lower voltage. To do this, I did a few things:
- Installed a normal 12V car charger with double USB output (one for the Apple TV, one for the HDMI to analog converter) in my glove compartment. I had this wired directly to the car to its own fuse in a shop as there is no 12V socket in the glove compartment. The purpose of this charger is to get the voltage from the 12-14V the car gives down to a more manageable 5V, which, if using a quality charger, should be stabilised voltage.
- I opened up the Apple TV and replaced its power source with a small chip that further lowers the voltage from 5V to the 3.3V its internals require. See bottom of this article for details on how to do that.
After you got all of this done, it's just a matter of linking and configuring everything:
- Apple TV and HDMI to analog converter get power from the car charger in the glove compartment
- (4G-Enabled) WiFi router gets power from the 12V socket in the armrest (another 12V car charger required here, recommending also one with double USB output to also accommodate charging the iPhone while streaming)
- Link HDMI to analog converter to Apple TV with HDMI-HDMI cable
- Connect both iPhone and Apple TV to the WiFi router.
There are two ways of getting the audio & video from the iPhone to the MMI:
- AirPlay mirroring - this mirrors the entire iPhone screen and its audio output to the MMI, regardless of what's on the screen. This is great for stuff like navigation apps. What I usually do is start the navigation app (Google Maps, Waze, whatever), then open the Music app, Shuffle All and go back to the navigation app. This gets you both navigation and music through the MMI, just as if you were using the car's built-in navigation system.
- Audio & Video streaming - this is a much better way of playing movies as it uses a protocol that knows how to buffer data and all that good stuff. A bad connection in this scenario will just pause the video while buffering as opposed to simply skipping frames and jerky audio as you would get if using the normal live screen mirroring. Most apps support this kind of streaming and it's also built-in to the default video player in iOS. Apps that I tested and found to work fine are Youtube, Vimeo, HBO GO, other live TV apps from my country which are not really relevant for the US and so on. To start streaming, start the video normally on your iPhone and then look for the AirPlay icon - example
Now, for the fun part. Modifying the Apple TV to accept 5V DC power input
Needed parts & tools:
- Apple TV (duh)
- The chip that actually gets the voltage down to 3.3V. I used the LM1084 regulator in its 3.3V version. This is guaranteed to output 3.3V stabilized.
- An USB connector. I actually ended up using the USB female side of an USB cable I had laying around because I wasn't patient enough to wait another day to buy a normal connector :)
- Small & big screwdrivers
- Soldering iron
- Voltmeter
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Step 1, opening the Apple TV.
Insert a small flathead screwdriver between the rubber bottom and the plastic side somewhere between the center of the rear side and the UTP connector. Once you get it to popup a little bit, insert a bigger screwdriver and rotate it to widen the gap. Then, take out the small one and continue on until you get the entire bottom part to pop out. The thing is reasonably strong, don't worry too much about breaking something but take your time nevertheless.
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Continuing in next post as there's a 5-image limit per post...
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Originally Posted by awo
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