Connecting a phone over ADB

ADB is the way a computer talks to a phone over a cable. Through it Lusiesta Studio sees devices, captures the screen, installs apps and runs scenarios. This article covers how to connect a phone properly, how to tell that it worked, and what the states mean where a device is visible but does not work.

What ADB is in plain words

ADB (Android Debug Bridge) is a service bridge between the computer and an Android phone. A small background service (the adb server) runs on the computer, keeps the list of connected devices and passes commands to them. The phone only answers those commands if USB debugging is enabled on it and you have granted access to that particular computer.

There is no need to install ADB separately: it ships with Lusiesta Studio and lives next to the app. The service starts automatically when the program launches. The first start after a computer reboot can take a few seconds, and during that time Home shows the card "Looking for ADB devices" with the caption "The first ADB start after a reboot can take a few seconds.".

Connection order

1. Enable developer mode and USB debugging on the phone. There is no point going further without it: the phone will not appear in the list at all. The vendor-by-vendor walkthrough is in Developer mode and USB debugging.
2. Unlock the phone screen and keep it on.
3. Connect the phone to the computer with a cable that can transfer data, not just charge.
4. The "Allow USB debugging?" dialog appears on the phone screen, showing the computer's key fingerprint. Tick "Always allow from this computer" and tap "Allow".
5. Wait a few seconds: the device list in the app refreshes on its own, there is nothing to restart by hand.

The "Allow USB debugging?" dialog

This dialog is an Android safeguard. The phone remembers the key of that particular computer, so you confirm once per phone-plus-PC pair. The "Always allow from this computer" checkbox is exactly what saves the key: without it the prompt pops up on every reconnect and in the middle of a task, and any task running at that moment stalls on the system dialog.

The prompt comes back if you reinstall Windows, factory-reset the phone or tap "Revoke USB debugging authorizations" in the developer section. Nothing to worry about, just confirm it again.

Never tap "Deny" on farm phones. After a refusal the handset stays visible to ADB but in the unauthorized state, and the app will not be able to capture the picture or run a task until you reconnect the cable and confirm the prompt.

What a successful connection looks like

When everything lines up, the empty state on Home is replaced by a device tile:

• the tile header shows the device number and its serial number;
• the body of the tile shows live video from the phone screen; while the picture is coming up you see "Loading preview" with a spinner;
• clicking and dragging with the mouse right on the preview taps and swipes on the phone;
• in list mode the device shows "USB" in the CONNECTION column.

The device number is stable: "Number 3" is the same phone in the grid, in publishing and in warmup. If the picture never appears while the device itself is visible, that is a separate story, covered in the article about empty tiles with no preview.

USB mode: file transfer or charging only

Android can connect to a computer in different modes. Some firmware defaults to "Charging only", and then the phone is either invisible or behaves erratically.

1. Pull down the notification shade on the phone and find the USB connection notification.
2. Tap it and choose "File transfer" (MTP). Clear the "Charging only" option.
3. So that you do not have to do this every time, set "Default USB configuration" -> "File transfer" in the developer section.

If the prompt never appeared

• The phone screen is locked: the dialog only shows on an unlocked screen. Unlock it and replug the cable.
• USB debugging is off: without it the prompt will never appear and the phone simply will not be seen.
• A charge-only cable or a worn port: change the cable and the port, and ideally connect straight to the computer rather than through a hub. Cheap cables with no data wires are the classic reason for "the phone charges but nothing sees it".
• The computer was authorized earlier: then there should be no dialog at all and the device appears right away.
• Access was denied before: tap "Revoke USB debugging authorizations" in the developer section, then reconnect the cable and the prompt comes back.
• On Windows you sometimes need the manufacturer's USB driver (Xiaomi, Samsung and so on).

What unauthorized, offline and no permissions mean

These are ADB's own states, and the app spells them out in plain language. If a device is visible but not working, a yellow banner along the lines of "Phone found Redmi Note 10: ..." appears under the empty state on Home, and the tile of an offline device carries a short hint:

• unauthorized - the cable is there, but nobody tapped "Allow debugging from this computer" on the phone. The hint on the tile is "Confirm USB debugging on the phone". Cured by confirming the prompt on the screen.
• offline - the phone is in the list but does not answer commands. The hint is "Reconnect the cable or the USB port". Usually a bad contact, a USB port that fell asleep, or ADB stuck after a cable swap.
• no permissions - no rights to the USB device, which is a driver or system permissions question. The hint is "No USB access - reconnect the cable".
• recovery or sideload - the phone booted into something other than the normal mode, and ADB is not available for work. Reboot the handset into the system.

The app takes a short drop calmly: a device that was live moments ago keeps showing as online for a few seconds while it reconnects, and it usually comes back on its own.

What to do next

The phone is connected and visible, and one step is left before the first task: prepare the handset itself so that scenarios do not trip over the lock screen and system dialogs. That is what Preparing the phone for work is about. If the device stubbornly refuses to appear, the common cases are collected in The device does not connect or is not visible.