Test-AC

External RTK coordinate via CAN/RS232 interface with FMC650

Overview

Activating RTK (Real-Time Kinematic) coordinate acquisition enables the FMC650 device to process RTK data from CAN. When configured, the RTK module can provide high-precision coordinates using:

• RTK receiver via RS232
• RTK data via CAN
• Internal GNSS receiver (GNS) as fallback

The device automatically chooses the best available source based on configuration and data quality.

The following specifications indicate the minimum firmware and configurator version requirement to use RTK coordinate acquisition via CAN on FMC650.

• Platform: FM65
• Device: FMC650
• Firmware version: 03.01.03.Rev.228
• Configurator version: B.FMX6_R.192

Method of Operation

When the RTK option is enabled, the device always tries to use RTK sources first and falls back to internal GNSS if needed.

Source priority

1. RS232 (primary RTK source)

   • The device checks whether any COM port (COM1 or COM2) is configured in RTK mode.
   • If at least one COM port is configured for RTK and valid data is present, coordinates are taken from RS232.

2. CAN RTK (secondary RTK source)

   • If RS232 RTK data is not available or is invalid, the device checks the CAN RTK status.
   • If valid CAN RTK data is available, coordinates are taken from CAN.
   • A timing check is applied if the time difference between received CAN RTK frames is greater than 2 seconds. The device automatically switches to the internal GNSS receiver (GNS) to keep coordinates up to date.

3. Internal GNSS (GNS) Fallback

   • If neither RS232 nor CAN provide valid RTK data, the device uses the internal GNSS receiver (GNS) for coordinates.

4. RTK Disabled

   • If the RTK option is disabled, coordinates are always taken from the internal GNSS receiver.

RTK data from CAN

When CAN is used as the RTK source, the device reads:

• Latitude
• Longitude
• Altitude
• Ground speed
• Course

These values are taken from standard CAN messages designed for GNSS/RTK data. Exact PGNs and signal layouts depend on whether external RTK/ECD/ISOBUS system is being used.

Configurator Setup

This section describes how to enable RTK as a location source and configure RS232 and CAN usage through the Configurator.

Enabling RTK as a location source

1. Open the Configurator and connect to the FMC650 device.
2. Navigate to the System tab.
3. Find the option “Source Location from RTK” in the System Settings section.
4. Set this option to Enable.

When enabled, the device will use RTK data from RS232/CAN if available, with automatic fallback to internal GNSS.

For advanced configuration (e.g. via commands):

Source Location from RTK
Parameter ID: 55000
Values:

• 0 – Disabled (device uses only internal GNSS)
• 1 – Enabled (device uses RTK sources if available)

Configuring RS232 for RTK Use If you plan to use an external RTK receiver via RS232:

1. Open the RS232/RS485 tab in the Configurator.
2. For COM1 or COM2 (or both), set the mode to RTK.

Relevant parameter IDs:

• COM1 mode – Parameter ID 151
• COM2 mode – Parameter ID 173
• RTK mode – Value 60

If at least one COM port is configured to RTK mode and valid RTK data is received, the device will use RS232 as the main coordinate source.

Using CAN as the RTK Source CAN-based RTK is used in the following cases:

• None of the RS232 COM ports are configured in RTK mode, or
• RS232 RTK data is not valid or not present.

When those conditions are met and valid CAN RTK data is received:

• The device uses CAN as the coordinate source.
• The device continuously monitors the time between RTK messages.
• If CAN RTK messages are delayed by more than 2 seconds, the device automatically reverts to internal GNSS to avoid stale coordinates.

RTK data taken from CAN includes:

• Latitude
• Longitude
• Altitude
• Ground speed
• Course

Configuration of RTK over CAN (e.g. PGN, source address, bitrate) depends on your external CAN/ISOBUS/RTK infrastructure and should follow that system’sdocumentation.

ISOBUS Data Visibility When used in ISOBUS or similar environments:

• RTK-related data from CAN is visible in the ISOBUS section of the Configurator.

• This allows you to verify that RTK data is being received and interpreted correctly by the device.

Active Location Source Monitoring

To understand which source is currently being used for position data, you can check the Location Source parameter.

Location Source Values

In the Configurator:

1. Navigate to the I/O tab (or equivalent I/O monitoring view).
2. Find the parameter Location Source.

Possible values:

• 0 – GNS

Location is taken from the internal GNSS receiver. This is the default when RTK is disabled or when no valid RTK data is available.

• 1 – RS232

Location is taken from the RTK receiver connected via RS232.

• 2 – CAN

Location is taken from RTK data arriving over CAN.

• 3 – Err

Location is taken from the internal GNSS receiver, but this status indicates that RTK data from RS232 and/or CAN is invalid or unavailable. This helps distinguish normal GNSS use from “RTK expected but not available” situations.

This parameter is used for diagnostics and for confirming that your device is using the intended RTK source.

NMEA Fix Type Monitoring (RS232 RTK Only)

When RTK coordinates are received via RS232, you can also monitor the NMEA Fix Type to understand the quality of the GNSS/RTK fix.

Configurator Steps

1. Open the Configurator.
2. Go to the I/O tab (or relevant section).
3. Locate the parameter NMEA Fix Type.

Note: This parameter is only available when coordinate data is received via RS232 RTK.

NMEA Fix Type Values

• NotValid - No valid GNSS fix is available.
  

• GPS - Standard GPS fix using satellites only.
  

• DGNSS - Differential GNSS fix (e.g. DGNSS, SBAS, etc.).
  

• NotApplicable - Fix quality is not applicable in the current context.
  

• RTK_Fixed - RTK Fixed; high-precision RTK fix (including xFill if supported by the receiver).
  

• RTK_Float - RTK Float; typically, a converging RTK solution or similar intermediate status.
  

• INS_DR - INS Dead Reckoning; position estimated by inertial sensors and previous GNSS/RTK data.
  

This information is beneficial for:

• Verifying that the external RTK receiver is working correctly.
• Assessing overall RTK performance and stability.
• Logging and diagnostics in advanced deployments.

Parameter IDs and AVL IDs

Below is a list of AVL IDs and Configurator IDs assigned to a specific item.

Name	Parameter ID	AVL ID
RTK Longitude	151790	14145
RTK Latitude	151800	14146
RTK Altitude	151810	14147
RTK Speed	151820	14148
RTK Angle	151830	14149
Source Location from RTK	55000	-
Source Location from RTK	55000	-
Location Source	53050	10919
NMEA Fix Type	53060	10920