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Pair your TeleBT v4 with AltosUI on iPhone

First-time pairing between AltosUI and a TeleBT is usually a two-minute job once the hardware is right. The single most common problem is a pre-v4 receiver that physically cannot talk to iOS the way AltosUI needs. This guide walks you through verifying your hardware, pairing over Bluetooth LE, and what to check first when the app and receiver refuse to see each other.

Hardware check: this only works with TeleBT v4

AltosUI on iOS is the iOS ground-station app for TeleBT v4. Earlier TeleBT models used a different Bluetooth protocol that iOS cannot connect to through the app. Before you do anything else, confirm your receiver is a v4 — serial number 3686 or higher. There are two ways to check.

Method A — by serial number. Look at the label on the board or the packaging. If the serial number is 3686 or higher, you have a v4. If it is lower, you do not.

Method B — over USB with the desktop terminal. Plug the TeleBT into a Mac, Windows, or Linux machine, open the desktop AltosUI, connect to the TeleBT’s serial device, and type the v command. The receiver reports its firmware and hardware identification. If that output identifies the board as v4, you are good. The FAQ has the canonical version of this answer.

If you have a pre-v4 TeleBT and want to fly with the iOS app, contact an Altus Metrum reseller through altusmetrum.org about upgrading.

Pairing the receiver

With a confirmed TeleBT v4 and a recent version of iOS on your iPhone or iPad, pairing happens entirely inside the app. You do not need to pair the TeleBT through iOS Settings first. AltosUI discovers TeleBT receivers over Bluetooth LE on its own and you tap the one you want to use right there in the app.

  1. Make sure Bluetooth is on for your phone. Control Center’s Bluetooth toggle or the Settings app both work.
  2. Power on the TeleBT v4.
  3. Open AltosUI. The app scans for nearby TeleBT receivers automatically and lists the ones it finds.
  4. Tap your TeleBT in that list to pair. iOS handles the BLE handshake — there is no PIN to type.
  5. In AltosUI, set the receiver to the frequency your airframe is flying on so the two radios agree.

Once that handshake completes, the Pad tab begins showing data from the receiver itself — its battery voltage, its location, its firmware version — even before any flight computer is in range. That is how you know the BLE link is healthy.

Why it won’t connect: the top five

When pairing fails or the app reports no telemetry, these five causes cover almost every case. Work through them in order.

  1. It isn’t a TeleBT v4. This is still the most common cause. Re-check the serial number or run the v command over USB. The FAQ covers the exact procedure.
  2. The flight computer woke in Idle mode instead of Pad mode. Altus Metrum flight computers decide which mode to wake in based on orientation at the instant of power-up: vertical — as if in the rocket — wakes in Pad mode and transmits. Horizontal (lying flat on a bench, say) wakes in Idle mode and will not transmit flight packets. This is by far the most common cause of “no receiver battery voltage, no telemetry” on a first-time setup. Fix: power the flight computer off, hold it vertical, power it on, and confirm on the Pad tab that telemetry is coming in. Once it’s in Pad mode you can lay it down again; the orientation check only matters at power-up. The FAQ has the canonical version.
  3. Wrong frequency. The receiver and the flight computer have to be on the same channel. Set the AltosUI frequency to match whatever the airframe is flying on.
  4. Bluetooth is off on the phone. Confirm Bluetooth is enabled from Control Center or the Settings app. Control Center can silence Bluetooth per-app in a way that looks like a connection problem; a quick toggle in Settings settles it.
  5. No receiver battery voltage on the Pad tab. If the TeleBT voltage doesn’t appear in the Pad view, the BLE link never completed. Power-cycle the TeleBT, go back to the device list in AltosUI, and tap your TeleBT again to re-establish the connection.

If you have worked through all five and still have no link, the support page has contact details and the steps for filing a reproducible report. Attach a screenshot of the Pad tab and note the TeleBT serial number in your message.

One note about radio licensing

The receiver side is Bluetooth — no license involved. The flight-computer side is a different story. To legally operate an Altus Metrum flight computer in the US, you need at least a Technician-class amateur radio license. Altus Metrum’s own page at altusmetrum.org/Radio is the canonical reference; the ARRL licensing page is the best starting point if you don’t already have a ticket.

What a healthy pairing looks like

Once the receiver is paired and AltosUI is open, a few specific pieces of data confirm the link is good even before a flight computer is powered on. On the Pad tab you should see the receiver’s battery voltage — that number comes out of the TeleBT itself, not the flight computer, so it tells you the BLE link is up. You should also see the receiver’s own location once iOS has a GPS fix for the phone. If those two fields are populated and the frequency selector shows the channel you expect, the ground side is ready.

When you then power up a flight computer in range, that receiver’s live telemetry begins filling in the rest of the Pad tab: arming status, per-channel pyro continuity, flight-computer battery, satellite count, firmware version. Two sides, two voltages, one frequency. That is what a working field setup reads like.

Working with several rockets at a club launch

AltosUI keeps a list of the rockets you’ve seen, with per-tracker callsign, frequency, and serial metadata that persists across app restarts and sorts by age, callsign, frequency, or serial number. At club launches where several flights go up in quick succession on different channels, that list is how you switch between them — you interact with one rocket at a time, and changing which one is active is a tap-and-frequency-change away. You don’t re-pair anything to switch; the BLE connection stays with the receiver, and the frequency selector just changes what the receiver is listening to.

Once you are paired

With a paired receiver and the frequency set, the rest of the field workflow falls into place. The launch-day checklist walks the full Pad → Flight → Map → Recover path, and the per-device guides pick up from there: TeleMetrum, TeleMega, TeleMini, and TeleGPS. For the bigger picture on how the iOS app fits next to the desktop workbench and AltosDroid, see AltosUI on iPhone: what it is (and what it isn’t). For the canonical TeleBT hardware reference, see altusmetrum.org/TeleBT.