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Manual · 02

Tablet & Network

Your tablet and phone connect directly to the SD Migrator Wi-Fi. This chapter shows how to set up the hotspot, give the Pi internet access on the road and prepare the tablet for permanent use as the controller.

The Pi opens its own encrypted Wi-Fi network (WPA2). Under Settings → Wi-Fi hotspot you configure:

  • Hotspot on or off
  • Network name
  • Password
  • Frequency band
  • Channel

Initial setup without tablet access

You don’t have a Wi-Fi connection to the Pi yet? Then you have two options:

  • Connect the Pi with a LAN cable and open https://<hostname>.local.
  • Open the settings page directly on the Pi via https://localhost.

How the hotspot works

  • In the hotspot, the Pi always has the address https://10.42.0.1. Tablet and phone receive their addresses automatically.
  • The hotspot starts automatically as soon as the Pi boots.
  • You can use a LAN cable at the same time.
  • Android connects automatically as soon as the Pi is running. For internet, the tablet keeps using mobile data as long as the Pi Wi-Fi offers no internet.

Choosing the frequency band

  • 2.4 GHz is the default. This band is permitted outdoors and has a long range.
  • 5 GHz (channels 36–48) is only permitted indoors in Germany.

Caution: The Pi’s Wi-Fi country code must be set (Germany: DE). You can check this on the Pi with sudo raspi-config nonint get_wifi_country.

Tip: When you save the hotspot settings, all connected devices are briefly disconnected. If you changed the name or password, reconnect the tablet.

Internet for the Pi (Wi-Fi client)

There is no LAN cable on the road. To still get the Pi online (e.g. for cloud uploads), connect it to a phone hotspot.

Adding a network

  1. Open Settings → Internet (Wi-Fi client).
  2. Search for networks or enter the network name.
  3. Enter the password.
  4. Tap Add.
  5. Choose the operating mode (see below).
  6. Tap Save & apply.

You can add several networks. The top network is preferred. The Pi connects to known networks automatically.

  • The interface never shows saved passwords again. To keep a password, leave the field empty.
  • Network scanning only works with an additional Wi-Fi dongle or with the fallback mode active (see operating modes). Otherwise, enter the network name manually.

Operating modes

  • Additional Wi-Fi adapter (recommended): A USB Wi-Fi dongle connects to the phone. The built-in chip remains undisturbed as the hotspot. Dongles that Linux supports without extra drivers are well suited, e.g. MediaTek MT7601U (2.4 GHz) or MT7612U/MT7921AU (2.4 + 5 GHz). Any Wi-Fi adapter other than the built-in chip is detected.
  • Share built-in chip (fallback): The built-in chip serves as both the connection to the phone and the hotspot. It only transmits on one channel. The Pi hotspot therefore follows the phone’s channel and restarts with every change – the tablet is then briefly disconnected. This mode is considered less stable.

Caution: In fallback mode, set the phone hotspot to 2.4 GHz. Otherwise the Pi hotspot also switches to 5 GHz – channels 36–48 are not permitted outdoors in Germany.

Sharing internet with hotspot devices

If the Pi has internet, the tablet and other devices in the Pi hotspot also go online through it. This applies to every internet connection of the Pi:

  • Wi-Fi client (e.g. 5G phone hotspot)
  • LAN cable
  • USB tethering from a phone

What counts is always the connection the Pi itself is currently using to reach the internet.

Don’t want this? Under Settings → Wi-Fi hotspot, switch off the option Share internet with hotspot devices. The SD Migrator interface remains accessible.

Connection status

The Internet (Wi-Fi client) page shows:

  • the available Wi-Fi adapters
  • the connected network and signal strength
  • whether the internet is reachable and via which connection
  • the network details of Wi-Fi client and LAN cable (IPv4, gateway, DNS, domain, IPv6, MAC)
  • the total data volume (received/sent) of Wi-Fi client and LAN cable since the Pi started or since the dongle was plugged in

Tip: The volume display helps you keep an eye on usage of your phone hotspot.

Testing the speed

Test speed measures latency, download and upload of the current internet connection. Afterwards you see:

  • roughly how long a cloud upload of 1 GB or 10 GB would take
  • a brief assessment of whether the upload is worthwhile
  • the data volume actually used, split into download and upload

A counter runs during the test. Each direction is limited to approx. 6 seconds. In total, the test uses at most approx. 36 MB (25 MB down, 11 MB up), considerably less on slow connections.

The measurement uses the connection shown as Connection. So if a LAN cable is plugged in, it measures over that.

Other options

  • Same Wi-Fi: Pi and tablet are on the same Wi-Fi network. Then open https://<hostname>.local or the Pi’s IP address.
  • USB tethering from the tablet: Connect the tablet to the Pi via USB. The cable must support data transfer – otherwise the switch on the tablet stays greyed out.

Caution: USB tethering puts load on the Pi’s USB power supply. The Pi’s address also changes.

Installing the HTTPS certificate on the tablet (once)

So that the browser recognises the connection to the Pi as secure, install the Pi’s certificate once.

Android

  1. Open http://10.42.0.1/ca.crt and download the file.
  2. Open Settings → Security → Encryption & credentials → Install a certificate → CA certificate.
  3. Select the downloaded file.

iOS

  1. Download ca.crt (same address as for Android).
  2. Install the profile.
  3. Open Settings → General → About → Certificate Trust Settings and enable full trust.

Adding it to the home screen as an app

  1. Open https://10.42.0.1 in Firefox.
  2. Tap ⋮ → Add to Home screen.

SD Migrator then starts without the browser bar (more space) and keeps the connection open for notifications.

Android app

Some launchers, e.g. the DMD2 Mini launcher, only show installed apps. For this case there is a lightweight Android app for SD Migrator. It is already included with SD Migrator.

Installing the app

  1. On the tablet, open http://10.42.0.1/sd-migrator.apk – or, in the browser under Settings, tap Install Android app.
  2. Confirm the installation.

The Install Android app button only appears in the browser on Android devices, not in the app itself. Notifications also work in the app.

Install and update button

  • Once you have opened the app via the Pi’s Wi-Fi, the Install Android app button disappears from the browser on the same tablet.
  • Until then, the button remains visible.
  • If your app is older than the bundled version, Update Android app appears – in the browser and in the app’s settings. The button opens the download in the Android browser and starts the installation.
  • Android uses a different device address on each Wi-Fi network. Detection therefore only applies to one network at a time.
  • The Pi cannot detect if the app has been uninstalled. After 30 days without contact from the app, the button reappears.

Caution: After changing the hostname, the Pi receives a new certificate. The Android app then no longer trusts the Pi and must be reconfigured.

Network security

Caution: By default there is no login. Anyone who can reach the Pi on the network can operate everything – including MOVE and deleting folders. Therefore only run SD Migrator in your own hotspot or a trusted network, and never make the Pi reachable from the internet.

SD Migrator rejects changes originating from third-party websites.

For shared networks, an access token can be set up. A login screen then appears where you enter the token. The token is only stored for the current browser session.