RTK Coordinate via CAN Integration 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.

How It Works

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

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

General Information

Platform: FM65
Device: FMC650
Firmware version: 03.01.03.Rev.227
Configurator version: B.FMX6_R.192

These versions indicate the minimum firmware and configurator level required to use RTK coordinate acquisition via CAN on FMC650.

Configurator Setup

This section describes how to enable RTK as a location source and configure RS232 and CAN usage through the Configurator. 4.1 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” 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 o Parameter ID: 55000 o Values: ▪ 0 – Disabled (device uses only internal GNSS) ▪ 1 – Enabled (device uses RTK sources if available) 4.2 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 • Value for RTK mode – 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. 4.3 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’s documentation. 4.4 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. 5. Monitoring the Active Location Source To understand which source is currently being used for position data, you can check the Location Source parameter. 5.1 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. o 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. o This helps distinguish normal GNSS use from “RTK expected but not available” situations. This parameter is especially useful for diagnostics and for confirming that your device is using the intended RTK source. 6. Monitoring NMEA Fix Type (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. 6.1 Where to find it 1. Open the Configurator. 2. Go to the I/O tab (or relevant section). 3. Locate the parameter “NMEA Fix Type”. This parameter is only available when coordinate data is received via RS232 RTK. 6.2 NMEA Fix Type values Value Description 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 helpful for: • Verifying that the external RTK receiver is working correctly • Assessing overall RTK performance and stability • Logging and diagnostics in advanced deployments 7. Parameter ID and AVL ID Below is a list of AVLID and Configurator ID assigned to specific item Name Parameter ID AVL ID RTK Longitude 151790 14145 RTK Latitud 151800 14146 RTK Altitude 151810 14147 RTK Speed 151820 14148 RTK Angle 151830 14149 Source Location from RTK 55000 - Location Source 53050 10919 NMEA Fix Type 53060 10920