continuousWave: Whaler: Reference: NMEA-2000 Parameter Groups Measurement

NMEA-2000 Parameter Groups

by James W. Hebert

An overview is presented of NMEA-2000 parameter groups, currently limited to two groups which contain engine data.

The NMEA-2000 Protocol

Detailed information about the NMEA-2000 protocol is difficult to obtain without purchasing expensive documents, which then require a non-disclosure agreement. The information below has been obtained from published information about NMEA-2000 parameter groups, and does not come from any sources which are restricted by non-disclosure agreements. I have collected the information from a variety of sources on the internet, and I simply aggregate it here for convenience.

In the NMEA-2000 protocol data is encapsulated into datagrams called parameter groups. The parameter groups are identified by number, and typically referred to their parameter group number or PGN. In order to clearly specify the capabilities of a particular device, manufacturers are more and more now including a NMEA-2000 PGN list to define what data their devices can receive from or send to the network.

Many modern outboard engines are certified for connection to NMEA-2000 networks. These modern engines transmit data about themselves to the network, where the data can be received by a variety of devices, processed, and displayed to an operator. An engine with NMEA-2000 certification will send data to the network. Once the data is on the network, there can be multiple devices listening for this data, and the same data can be displayed on several instruments or screens and in multiple places. The data can even be ingested and logged by a data logger. In the beginning of NMEA-2000 there were a limited number of engines which provided a NMEA-2000 port, and it was typical that the engine manufacturer would also provide the instrumentation to receive the data from the network. As the NMEA-2000 protocol became more popular, a variety of manufacturers began to produce NMEA-2000 instruments which could receive engine data from a network, and it is now common that data from an engine will be received and displayed on a device made by another manufacturer.

Engine Data in NMEA-2000

For engine data there are two parameter groups which provide data, PGN 127488 and PGN 127489. We now look at these PGN's in detail.

PGN 127488: Engine Parameters, Rapid Update

PGN 127488 provides data with a high update rate--ten times per second--about a limited number of engine parameters which are liable to rapidly change.

PGN 127488
Engine Parameter	Typical Display Range
Engine Speed	0 - 10,000 RPM
Boost Pressure	0 - 400 PSI
Tilt-Trim Position	0 - 100 %

Field Details

Field 1: Engine Instance (8-bit unsigned integer) This field indicates the particular engine for which this data applies. A single engine will have an instance of 0. Engines in multi-engine boats will be numbered starting at 0 at the bow of the boat incrementing to n going towards the stern of the boat. For engines at the same distance from the bow and stern, the engines are numbered starting from the port side and proceeding towards the starboard side.
Field 2: Engine Speed (16-bit unsigned integer) This field indicates the rotational speed of the engine in units of 1/4 RPM.
Field 3: Engine Boost Pressure (16-bit unsigned integer) This field indicates the turbocharger boost pressure in units of 100 Pa.
Field 4: Engine tilt/trim (8-bit signed integer) This field indicates the tilt or trim (positive or negative) of the engine in units of 1 percent.
Field 5: Reserved (16 bits) This field is reserved by NMEA; typically all 1's are sent.

PGN 127489: Engine Parameters, Dynamic

PGN 127489 carries data about a wide range of engine parameters with an update rate of once per second.

PGN 127488
Engine Parameter	Typical Display Range
Oil Pressure	0 - 400 PSI
Oil Temperature	0 - 500 ° F
Temperature	0 - 500 ° F
Alternator Volts	0 - 100 Volts
Fuel Rate	0 - 800 GPH
Total Hours	0 - 999999
Coolant Pressure	0 - 400 PSI
Fuel Pressure	0 - 400 PSI
STATUS INDICATORS
Check Engine	0 - 1 (OFF-ON)
Over Temp	0 - 1 (OFF-ON)
Low Oil Pressure	0 - 1 (OFF-ON)
Low Oil Level	0 - 1 (OFF-ON)
Low Fuel Pressure	0 - 1 (OFF-ON)
Low System Voltage	0 - 1 (OFF-ON)
Coolant Level	0 - 1 (OFF-ON)
Water Flow	0 - 1 (OFF-ON)
Water In Fuel	0 - 1 (OFF-ON)
Charge Indicator	0 - 1 (OFF-ON)
Preheat Indicator	0 - 1 (OFF-ON)
High Boost Pressure	0 - 1 (OFF-ON)
Rev Limit Exceeded	0 - 1 (OFF-ON)
EGR System	0 - 1 (OFF-ON)
Throttle Position Sensor	0 - 1 (OFF-ON)
Emergency Stop Mode	0 - 1 (OFF-ON)
Warning Level 1	0 - 1 (OFF-ON)
Warning Level 2	0 - 1 (OFF-ON)
Power Reduction	0 - 1 (OFF-ON)
Maintenance Needed	0 - 1 (OFF-ON)
Comm Error	0 - 1 (OFF-ON)
Sub or Secondary Throttle	0 - 1 (OFF-ON)
Engine Shutting Down	0 - 1 (OFF-ON)
Engine Parameter	Typical Display Range
Percent Load	0 - 100 %
Percent Torque	0 - 124 %

Field Details

Field 1: Engine Instance (8-bit unsigned integer) This field indicates the particular engine for which this data applies. A single engine will have an instance of 0. Engines in multi-engine boats will be numbered starting at 0 at the bow of the boat incrementing to n going towards the stern of the boat. For engines at the same distance from the bow and stern, the engines are numbered starting from the port side and proceeding towards the starboard side.
Field 2: Engine Oil Pressure (16-bit unsigned integer) This field indicates the oil pressure of the engine in units of 100 Pa.
Field 3: Engine Oil Temperature (16-bit unsigned integer) This field indicates the oil temperature of the engine in units of 0.1°K.
Field 4: Engine Temperature (16-bit unsigned integer) This field indicates the temperature of the engine coolant in units of 0.1°K.
Field 5: Alternator Potential (16-bit signed integer) This field indicates the alternator voltage in units of 0.01V.
Field 6: Fuel Rate (16-bit signed integer) This field indicates the fuel consumption rate of the engine in units of 0.0001 cubic-meters/hour.
Field 7: Total Engine Hours (32-bit unsigned integer) This field indicates the cumulative runtime of the engine in units of 1 second.
Field 8: Engine Coolant Pressure (16-bit unsigned integer) This field indicates the pressure of the engine coolant in units of 100 Pa.
Field 9: Fuel Pressure (16-bit unsigned integer) This field indicates the pressure of the engine fuel in units of 1000 Pa.
Field 10: Reserved (8 bits) This field is reserved by NMEA; typically all bits sent as a logic 1.
Field 11: Engine Discrete Status 1 (16 bits) This field indicates warning conditions of the engine with the following bit assignments (value of 1 indicates warning present):
- Bit 0: Check Engine
- Bit 1: Over Temperature
- Bit 2: Low Oil Pressure
- Bit 3: Low Oil Level
- Bit 4: Low Fuel Pressure
- Bit 5: Low System Voltage
- Bit 6: Low Coolant Level
- Bit 7: Water Flow
- Bit 8: Water in Fuel
- Bit 9: Charge Indicator
- Bit 10: Preheat Indicator
- Bit 11: High Boost Pressure
- Bit 12: Rev Limit Exceeded
- Bit 13: EGR System
- Bit 14: Throttle Position Sensor
- Bit 15: Emergency Stop Mode
Field 12: Engine Discrete Status 2 – (16 bits) This field indicates warning conditions of the engine with the following bit assignments (value of 1 indicates warning present):
- Bit 0: Warning Level 1
- Bit 1: Warning Level 2
- Bit 2: Power Reduction
- Bit 3: Maintenance Needed
- Bit 4: Engine Comm Error
- Bit 5: Sub or Secondary Throttle
- Bit 6: Neutral Start Protect
- Bit 7: Engine Shutting Down
- Bit 8-15: These bits are reserved and should be masked when read
Field 13: Percent Engine Load (8-bit signed integer) This field indicates the percent load of the engine in units of 1 percent.
Field 14: Percent Engine Torque (8-bit signed integer) This field indicates the percent torque of the engine in units of 1 percent.

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Last modified: Tuesday, 14-Feb-2012 09:19:12 EST
Author: James W. Hebert
This article first appeared February 12, 2012.