ECU TPMS

TPMS or Tire Pressure Monitoring Systems can be connected to the Syrus 4 in order to monitor tire pressures and alerts.

Doran's 360 System and Continental's ContiPressureCheck both make use of standard J1939 PGNs so all we need to do is install the sensor on the vehicle, and connect the Primary or Secondary CAN interfaces from the Syrus to the CAN Bus to start reading data.

Installation

Syrus 4 Datasheet with Pinout

Doran 360

Manufacturer's installation guide

Note that installing a terminating resistor may be needed depending on what accessories you connect to the Syrus over the CAN bus. For more informationclick here .

Continental CPC

Manufacturer's installation guide

Guide: Doran 360 System

For this example we'll connect the Doran 360 System to the Syrus. After following the manufacturer's installation guide above, connect the Syrus to the CAN bus via the secondary CAN interface:

ECU Wiring Pinout (found in 14-pin molex)

Configuration

The TPMS configuration can be achieved by adding the FEF4 PGN parameters to the ecumonitor.conf file

START_SECTION: CONFIGURATION
PRIMARY_CAN: J1939_250KHZ
END_SECTION

START_SECTION: J1939
PARAM_NAME: TIRE1 - EXTENDED TIRE PRESSURE SUPPORT, PGN: FEF4, TRANSMISSION_RATE: 10S, PRIORITY: 6, DLC: 8, LENGTH: 2_BITS, START_POSITION: 5.7, GROUP: LOCATION_COMPONENT_1, MULTIPLIER: 1
PARAM_NAME: TIRE1 - TIRE LOCATION, PGN: FEF4, TRANSMISSION_RATE: 10S, PRIORITY: 6, DLC: 8, LENGTH: 8_BITS, START_POSITION: 1, GROUP: LOCATION_COMPONENT_1, MULTIPLIER: 1
PARAM_NAME: TIRE1 - TIRE PRESSURE THRESHOLD DETECTION, PGN: FEF4, TRANSMISSION_RATE: 10S, PRIORITY: 6, DLC: 8, LENGTH: 3_BITS, START_POSITION: 8.6, GROUP: LOCATION_COMPONENT_1, MULTIPLIER: 1
PARAM_NAME: TIRE1 - TIRE PRESSURE, PGN: FEF4, TRANSMISSION_RATE: 10S, PRIORITY: 6, DLC: 8, LENGTH: 1_BYTE, START_POSITION: 2, GROUP: LOCATION_COMPONENT_1, MULTIPLIER: 4
PARAM_NAME: TIRE1 - TIRE SENSOR ENABLE STATUS, PGN: FEF4, TRANSMISSION_RATE: 10S, PRIORITY: 6, DLC: 8, LENGTH: 2_BITS, START_POSITION: 5.1, GROUP: LOCATION_COMPONENT_1, MULTIPLIER: 1
PARAM_NAME: TIRE1 - TIRE STATUS, PGN: FEF4, TRANSMISSION_RATE: 10S, PRIORITY: 6, DLC: 8, LENGTH: 2_BITS, START_POSITION: 5.3, GROUP: LOCATION_COMPONENT_1, MULTIPLIER: 1
PARAM_NAME: TIRE1 - TIRE TEMPERATURE, PGN: FEF4, TRANSMISSION_RATE: 10S, PRIORITY: 6, DLC: 8, LENGTH: 2_BYTES, START_POSITION: 3-4, GROUP: LOCATION_COMPONENT_1, MULTIPLIER: 0.03125, OFFSET: -273
PARAM_NAME: TIRE1 - TRAILER FLAG, PGN: FEF4, TRANSMISSION_RATE: 10S, PRIORITY: 6, DLC: 8, LENGTH: 2_BITS, START_POSITION: 8.1, GROUP: LOCATION_COMPONENT_1, MULTIPLIER: 1
END_SECTION

Once the Syrus has the configuration file, and you install the TPMS sensor on the vehicle you can trigger messages using Syruslang - sample snippet.

You can also use the apx-ecu tool to view the parameters.

# List ECU parameters, indicating tpms data from 6 tires
$ sudo apx-ecu list_parameters
{
fef4_8.1: "0,2,1.00;0,1,1.00;1,3,1.00;1,2,1.00;1,1,1.00;1,0,1.00",
fef4_8.6: "0,2,0.00;0,1,0.00;1,3,0.00;1,2,0.00;1,1,0.00;1,0,0.00",
fef4_2: "0,2,860.00;0,1,965.00;1,3,825.00;1,1,890.00;1,0,825.00;1,2,885.00",
fef4_5.1: "0,3,1.00;0,0,1.00",
fef4_3-4: "0,2,30.00;0,1,36.00;1,3,34.00;1,1,34.00;1,0,36.00;1,2,30.00",
fef4_1: "0,2,2.00;0,1,1.00;1,3,19.00;1,2,18.00;1,1,17.00;1,0,16.00",
fef4_5.3: "0,2,3.00;0,1,3.00;1,3,3.00;1,2,3.00;1,1,3.00;1,0,3.00",
fef4_5.7: "0,2,0.00;0,1,0.00;1,3,0.00;1,2,0.00;1,1,0.00;1,0,0.00"
}

SERIAL TPMS

PressurePro is a Tire Pressure Monitoring Systems (TPMS) designed to provide real-time tire performance data for safety and efficiency. The system consists of sealed sensors that screw directly onto tire valve stems and a display monitor.

The syrus PressurePro driver communicates with a PressurePro TPMS gateway over the FlexIO protocol. The gateway receives data from the tire sensors; syrus reads that data and exposes the latest decoded snapshot through Redis.

The implementation uses the serial port at 9600 baud, 8 data bits, no parity, 1 stop bit (8N1). Connect the gateway's RS232 interface to the user serial port.

Enable the driver

Set the serial manager mode:

apx-serial mode pressurepro

Command-line utility

For example:

apx-serial-pp get --unit
apx-serial-pp state

If no state has been written to Redis yet, state prints []. Invalid command options return exit status 95.

Driver behavior

On startup, the driver reads the configured unit and performs this sequence:

1. Send Get ID and confirm the response identifies a TPMS unit.
2. Send Get Version for the configured unit and log the returned version.
3. Request Get Sensor Data using command 0x83 and subcommand 0x13.

The driver requests data when it has not received automatic sensor data recently. The fallback polling interval is 10 seconds; incoming automatic sensor-data frames (response 0x93) are also accepted and refresh that timer. The driver retries unanswered commands up to three times. If no valid frame is received for 30 seconds, it marks the link disconnected and republishes the last cached snapshot with connected: false.

FlexIO frames use STX/ETX delimiters, a little-endian length, and an 8-bit additive checksum. The driver validates frames before processing them and ignores malformed or checksum-invalid frames.

Redis state

The latest snapshot is stored at serial_tpms_state and published on serial/notification/tpms/state. The state utility reads the stored value.

Example:

{
  "system_epoch": 1780000000,
  "last_contact": 2,
  "connected": true,
  "wheels": 1,
  "axles": 1,
  "tires": [
    {
      "sensor_id": 66051,
      "location": 17,
      "temperature": 32,
      "psi": 95,
      "reference_psi": 100,
      "rf_quality": 72,
      "new_air": false,
      "timeout": 1,
      "alarm_flags": 0
    }
  ]
}

The example is illustrative; the driver includes one tires entry per populated location. Fields are:

The alarm_flags bit meanings are:

To test a flag, apply its mask to alarm_flags; for example, under-pressure is set when alarm_flags & 0x10 is nonzero.

Troubleshooting