Vehicle Anchor
Vehicle-mounted RTLS device for collision avoidance and proximity detection (CAS-PDS) and location tracking.
The unit is mounted on the machine. It answers ranging requests from nearby tags and vehicles and delivers proximity results over the local bus or BLE, without a backend round trip.
Interfaces
| Interface | Notes |
|---|---|
| CAS-PDS Protocol | the operating mode of this device |
| UWB TWR | proximity ranging |
| UWB TDoA | selected by UWB RTLS method 0x5106 |
| Offline-online RMA | topological position from fixed beacons |
| Unified TDMA | schedule parameters 0x71–0x76 |
| BLE GATT | configuration and range notifications |
| GATT Data Sync | 0x5130 / 0x5131 |
| Sensor TLV | produce and decode / forward |
| BLE Ext Advertising | sensor carrier 0x7C = 1 |
| CAN-FD | daisy chain; RS-485 also available |
| MQTT | published by the chain master |
| OTA Upgrade | single signed ZIP over BLE; nRF52 and WiFi module |
CAS-PDS mode
The Vehicle Anchor is the same platform and firmware image as the Fieldbus Anchor, placed in CAS-PDS mode. Node mode (0x512D) selects it:
| Value | Node mode |
|---|---|
0 | RTLS anchor — Fieldbus Anchor |
1 | RTLS tag |
2 | CAS-PDS anchor — Vehicle Anchor |
3 | CAS-PDS tag |
The setting takes effect after restart.
How results are delivered
In CAS-PDS mode the anchor responds to blink and poll frames. Delivery depends on the unit's chain role (anchor UART role 0x5119):
| Role | Own ranges | Chain ranges |
|---|---|---|
| Master (RX) | BLE GATT notification | BLE GATT notification |
| Slave (TX) | RS-485 or CAN | — |
The Android tablet application in the cab subscribes to the GATT notifications, as can any third-party application written against the same characteristics — the anchor is a BLE peripheral and serves whichever application connects. Range data never leaves the vehicle. Position and telemetry reach the backend separately, over MQTT through the chain master.
Full protocol detail, including the vehicle-state parameter and the notification format: CAS-PDS Protocol.
Offline position tracking
Alongside UWB proximity, the Vehicle Anchor implements Offline-online RMA, reporting the vehicle's position against matchpoints — virtual reference points placed on the portal map to correspond to known fixed points on the site, such as survey pegs. This path requires no UWB infrastructure along the route, continues without network coverage, and reaches the backend as a position with DeviceType: "bler".
Power supply
The enclosure holds two boards: the RTLS board carrying the MCU, radios and fieldbus controllers, and a separate PSU board that conditions the incoming supply and feeds it. This is the same PSU board fitted to the Fieldbus Anchor — the two products share a platform.
Running from vehicle power
| Input range | 7–28 V DC |
| Field wiring | WAGO 236-401 spring terminal blocks |
| To the RTLS board | 4-pin 2.54 mm board-to-board connector |
The range covers both vehicle electrical systems in normal use: 12 V on cars and light vehicles, 24 V on trucks and heavy machinery. It also absorbs the everyday variation either system shows — a rail sagging during cranking, or sitting high while the alternator charges — so the anchor does not need a dedicated converter per vehicle class.
Regulation
An MP1584EN synchronous step-down converter, adjustable output, rated 3 A, with a 22 µH inductor and Schottky rectification (30 V, 3 A). A buck topology rather than a linear regulator is what makes the wide input range practical — dropping 28 V to a logic rail linearly would dissipate the difference as heat inside a sealed enclosure on a machine that is already hot.
Protection
The input is protected by an overvoltage crowbar: a TL431 precision shunt reference watching the rail, triggering a BT151 thyristor (650 V, 12 A) that shorts the input and clears the fuse if the voltage exceeds the design window. The protection circuitry is duplicated, so a fault on one path does not leave the other unguarded.
A crowbar fails safe and loud: an overvoltage becomes an open fuse rather than a damaged board. On a vehicle this is the intended behaviour for a transient beyond the input window — the anchor stops and the reason is visible on inspection, instead of surviving degraded and failing later as unexplained radio faults.
Vehicle electrical systems can produce transients well outside the input range — load dump being the obvious one. Where that risk exists, fit protection upstream of the anchor rather than relying on the crowbar, whose job is to protect the board, not to keep the anchor running through the event.