BLE framing

Use SimpleBLE, NimBLE, or the Arduino BLE stack for scan and GATT. Feed indication bytes into BleFrame and write BuildRoutableMessage output to the write characteristic.

Find the car

Common::calculateIdentifier turns the 17-byte VIN into the BLE advertisement name (Tesla protocol.md S1…C form). Scan until a peripheral matches that name.

GATT

Role	UUID
Service	00000211-b2d1-43f0-9b88-960cebf8b91e
Write	00000212-b2d1-43f0-9b88-960cebf8b91e
Indicate	00000213-b2d1-43f0-9b88-960cebf8b91e

Length prefix

Every Tesla BLE payload starts with a 2-byte big-endian length, then that many protobuf bytes. BuildRoutableMessage already prepends it. Common::ExtractLength / PrependLength exist if you need them by hand.

ATT fragments

Indications can split a message across packets. The first chunk must include the 2-byte length prefix. BleFrame::Add strips that prefix. COMPLETE means Payload() / PayloadSize() is the RoutableMessage protobuf only. ERROR means reset. NEED_MORE means wait.

TeslaBLE::BleFrame frame;
auto status = frame.Add(chunk, chunk_size);
if (status == TeslaBLE::BleFrame::COMPLETE) {
    UniversalMessage_RoutableMessage msg = UniversalMessage_RoutableMessage_init_zero;
    TeslaBLE::Common::DecodeRoutableMessage(
        const_cast<unsigned char *>(frame.Payload()),
        frame.PayloadSize(),
        &msg);
    frame.Reset();
}

See examples/simple and examples/esp32 for a full scan-connect-indicate loop.