Setting up the MasterLink: hotspot, Wi-Fi and first connection

The MasterLink has no screen and no keyboard, so setting it up comes down to one job: telling it which Wi-Fi network to join. You do that once, it takes about five minutes, and after that it rejoins on its own every time you turn the key. This page covers what the unit is, how it gets onto a network, how the app finds it, how to power it, and the handful of snags that cause nearly every failed setup.

What the MasterLink is, and which boards run it

The MasterLink is a small Raspberry Pi computer that I set up to talk to older cars in the languages a Bluetooth dongle cannot speak. On the car side it uses a USB K+DCAN cable plugged into the diagnostic port. On the phone side it talks to The Analogue over Wi-Fi. Today its proven job is BMW's DS2 body bus on K-line cars such as the E39: the cluster, lights, immobiliser, climate and stability control. It is a K-line device. It has no CAN hardware, so on an E9x or newer BMW a Bluetooth adapter is the right tool.

The software card is not tied to one board, but I only call a board supported once it has booted, activated its license and read a real car.

The supply figures are Raspberry Pi's own. If you build your own, one more thing to know: the license locks to the board the first time it comes online, so a card moved to a different Pi will not activate again on its own. That is what keeps your unit yours.

Giving it Wi-Fi: your hotspot or your home network

Plug the cable into the MasterLink and the other end into the car's port, give it power, and switch the ignition on. The engine does not need to run. Then wait a full 90 seconds. For the first 45 or so it looks for a network it already knows, and checking at 20 seconds is the most common reason setup seems broken.

You then choose where it lives. Your phone's hotspot means it works anywhere the car goes. Your home Wi-Fi works if the car gets a signal in the driveway or garage. Either way it needs the internet once, to activate its license with my server. After that it runs from what it already knows, and reading your car uses no mobile data at all.

iPhone: over Bluetooth, inside the app

1. Update The Analogue if the App Store offers an update. Bluetooth setup does not exist in the oldest builds.
2. Open Settings, MasterLink, Set up over Bluetooth.
3. Tap your unit, MasterLink-XXXX, and tap Pair when iOS asks.
4. Type the network name and password exactly as they appear on the router, or in Settings, Personal Hotspot. Your license key is already filled in.
5. Watch it move through receiving, connecting and activating to online.

Android: the unit's own setup page

1. In your phone's Wi-Fi settings, join MasterLink-Setup-XXXX with the password analogue. It will say there is no internet. Stay on it.
2. In a browser, type http://192.168.4.1 with the http:// in front.
3. Enter the name and password of the network it should live on, add your license key, and save.
4. Leave it powered for about ten minutes. It collects a firmware update on its own, and on Android that update is what lets the app reach it.

Yes, you can type your home Wi-Fi into that page while your phone has no internet. The page is served by the MasterLink itself.

How the app finds it

Once your unit is online it reports its address on your network to my server under its own name, and the app reads that address back from your account. So you never type an IP address, and it does not matter that a phone hotspot hands out a different one each time. I stopped relying on the old masterlink.local style of name because it proved unreliable on phone hotspots.

On iPhone, tapping Connect to your car and picking MasterLink tries Wi-Fi first, then looks for the unit on the network, then falls back to Bluetooth. That Bluetooth path is new: it is built, but I have not yet proven it end to end on a car, and it will be slower than Wi-Fi. Use Wi-Fi whenever you have it. On Android, the app reaches the unit over a secure connection the unit itself serves, which is why that first firmware update matters.

If the car is parked in range of your house and the unit lives on your home Wi-Fi, put your phone on the same network before you tap Connect. That gives the quickest live data.

Power

On the cars most owners bring to it, the E36, E39 and E46 among them, the MasterLink is powered from the 12 V socket inside the car with a good USB car charger. Choose a supply that holds a steady 5 V with enough current: Raspberry Pi recommends 2.5 A for the 3A+, and my setup page asks for a 12 V adapter rated 2.4 A or better, with 3 A ideal. Raspberry Pi warns that a low quality supply can corrupt storage or cause unpredictable behaviour, and in practice that looks like random reboots or a unit that connects and then drops.

Some BMWs put the diagnostic socket under the bonnet: the round 20-pin socket on the E34, E36, E38 and Z3, and on E39, E46 and E53 cars built before late 2000. If you would rather leave the MasterLink in the engine bay on those cars, heat and power need a little thought.

• Mount it in the coolest spot you can find, away from the exhaust side, under a heat shield such as reflective heat-shield tape or sleeve.
• Power it from a USB power bank, or wire it in.
• To wire it in: an add-a-fuse tap in the fuse box, a 5 A fuse, a waterproof 12 V to USB-C converter rated 5 V, 3 A, and the ground to a body stud.
• Run the wires along the existing loom.

The Pi 3A+ and Zero 2 W take micro USB, so a USB-C converter needs a USB-C to micro USB lead for those boards.

When it will not connect

Nine times out of ten it is the hotspot. Work down this list in order.

• It cannot find my iPhone hotspot. In Settings, Personal Hotspot, turn on Allow Others to Join (the Control Center button does not do this) and Maximize Compatibility. Stay on that screen during setup, because the iPhone quietly drops the hotspot when you leave it.
• It saved, but never came online. The network name or password was off by one character. Check capitals, a trailing space, autocorrect capitalising your password, and the curly apostrophe in a name like Nikita's iPhone.
• It asks me for a PIN. You are in the phone's Bluetooth settings. Never pair it there. Find it in The Analogue under Settings, MasterLink.
• I cannot find MasterLink-Setup. You looked before 90 seconds were up, the supply is weak, or it already joined a network it knows.
• 192.168.4.1 does nothing. Type the http:// part, and check you are still on the MasterLink-Setup network.
• It says there is no MasterLink on this account yet. It has not reached my server yet. Finish setup and it clears itself.
• It connected, then dropped, or keeps restarting. Power. Try a known good wall supply on the bench to prove the unit is healthy, then fix the supply in the car.
• My home router never shows up. The card is set to US radio rules, which hide 2.4 GHz channels 12 and 13. If your router uses one of those, move it to channel 11 or lower.
• It is online, but will not read the car. Seat the cable fully and turn the ignition on. On a BMW with the round 20-pin socket, use a fully pinned 20-pin adapter. Cheap partial adapters do not carry the diagnostic lines.