Automotive Bluetooth Digital Key Solution

The automotive Bluetooth digital key solution uses a multi-point Bluetooth (BLE) listening architecture: multiple listening anchors capture the RSSI of the Bluetooth signal exchanged between the key and the central node in order to locate the key.

This solution lets a smartphone be used directly as the car key; only a single Bluetooth connection between the key and the central node is needed to achieve hands-free unlocking.

By using Bluetooth frequency hopping together with security and encryption mechanisms (identity authentication, device binding and pairing, link encryption, etc.), the solution improves security, enables position awareness between the user and the vehicle and hands-free vehicle unlocking, matches the trend toward smart mobility, and enhances the user experience.

Solution Overview

The central node and the listening nodes use an automotive-grade RF MCU that supports BLE 5.0 and integrates a FlexCAN peripheral; each node also carries a CAN transceiver on board, so it can be seamlessly integrated into the vehicle's CAN communication network. The central node supports up to 4 simultaneous connections.

Deployment

The central node has a built-in positioning algorithm that calculates the zone the key is located in from the RSSI data reported by the listening nodes, and the result can be output over UART, CAN or Bluetooth as required.

4-node layout

5-node layout

Key Features

• Only a single Bluetooth link between the key and the central node is required
• Supports smartphones or Bluetooth modules with BLE 4.0 or above as the key
• Rich set of example programs; the central node acts only as a slave
• The listening nodes operate at RF level and do not need to implement the Bluetooth protocol stack or related functions
• Bluetooth frequency hopping across 37 channels
• Supports identity authentication, device pairing and encrypted link communication
• Configurable as 4 or 5 nodes, supporting up to 4 keys connected simultaneously
• Millisecond-level filtering algorithm latency delivers positioning results quickly, with smooth, jitter-free zone detection

Reference Design Digital Anchor-P

• Includes a FlexCAN module
• Includes a LIN module
• Provides a GENFSK hardware link layer to implement the listening function
• -95 dBm receive sensitivity