Why a bus project is an integration project, not a product purchase
A bus builder does not want another screen in the cab. It already has a body controller, a
dashboard and a diagnostic port. What it wants from a TPMS is: **four or six numbers and an alarm
flag, on the existing bus, readable by the existing controller.**
So the unit of delivery is not "a kit". It is:
| Item | What it has to be |
|---|---|
| Sensors | 433.92 MHz, one per wheel, external valve or internal band |
| Receiver | One node on the vehicle, one interface fitted at build |
| Message set | Documented, mapped to the body controller's expected IDs |
| Alarm | A decision the controller can act on, not a buzzer nobody hears |
| Evidence | A CAN log from a real bus, not a bench video |
4-wheel and 6-wheel buses are different jobs
On a 4-wheel bus (two axles, single tyres) the map is trivial: 11 / 12 / 21 / 22. One receiver,
four sensors, no repeater in most cases.
On a 6-wheel bus there is usually a tag or pusher axle. Two configurations appear in practice:
- 6 single tyres → six positions, one sensor each.
- Rear dual pair → six positions, and the inner tyre needs its own sensor, which is the
detail that turns up late in a project.
What the pairing step looks like on a real bus — front, rear and tag axle, one handheld tool:
- Bus TPMS sensor pairing — 4 wheels, one handheld tool
- 6-wheel bus TPMS pairing — front, rear and tag axle
Those two clips are the boring part that decides whether the project is finished on time: each
sensor is identified to a position, and the position record matches the drawing.
What to agree with the bus builder before the first unit
1. Which node is the master. Our receiver is a Modbus RTU slave on RS485 or a CAN node —
in both cases the vehicle controller polls us. We do not poll the vehicle.
2. The message set. CAN 2.0B, 11-bit or 29-bit extended. **We have deployed J1939-format
message sets in construction machinery integrations with major OEMs**; for a bus programme we
map to the builder's DBC or parameter list. We do not claim J1939 certification.
3. What the alarm means. Low pressure threshold, high temperature threshold, sensor-missing
timeout — three numbers that must be agreed, not defaults left in a factory menu.
4. Where the receiver physically goes. Not behind the dashboard by default. Low on the chassis,
open, near the axles — otherwise the last wheels in a 6-wheel bus are the ones that suffer.
5. Who owns the wheel map. The wheel map should be a document on the vehicle file, not a
photo on somebody's phone.
Interface reality: one per receiver
A receiver is built with one interface: CAN 2.0B, RS485 (Modbus RTU slave), RS232/UART,
PROFINET via a gateway, or USB-UART. If a project genuinely needs CAN and RS232 at the same time,
that is two receivers or a project-specific build — this is worth settling in the RFQ stage rather
than discovering at the integration bench.
What the bus builder gets that a screen does not give
- One node and one message set to validate, instead of a second display to mount and power.
- Each wheel's pressure, temperature, sensor ID and status, on the same bus the diagnostics tool
already reads.
- A log they can hand to the operator when a tyre is questioned.
FAQ
Can the bus keep its existing dashboard? Yes. The TPMS data goes onto the bus; whether the
builder shows it on the existing display, a new page, or only in diagnostics is their decision.
Do you supply the display too? We can supply 7-inch, dot-matrix and segment displays, but a bus
programme usually does not need one. The receiver is the part that matters.
Is J1939 supported? We support 29-bit extended frames and have deployed J1939-format message
sets; we map to your DBC. We do not claim J1939 conformance certification.
How many wheels can one receiver handle? Up to 256 positions — far beyond a bus, which is the
point: the same receiver part serves a bus, a truck fleet and a 160-wheel beam carrier.
Can we test before the vehicle is built? Yes: bench integration with your controller and our
receiver, using the message set we would ship. That is the cheapest place to find a mapping error.