This article describes how to interface the MTi-680(G) with the Racelogic VBOX NTRIP modem in order to receive the RTK corrections from an NTRIP client.
NTRIP (Networked Transport of RTCM via Internet Protocol) is a protocol that enables streaming of RTK correction data via the internet over common TCP/IP methods. These NTRIP services can be accessed via paid subscription or free-to-use broadcasters. Here you can find a list of NTRIP casters and providers in different parts of the word: https://ntrip-list.com/
The Racelogic VBOX NTRIP is part of the Racelogic VBOX Systems which are used by vehicle and tyre manufacturers for testing and validating a vehicle’s performance, handling and safety systems. This NTRIP modem is used to receive positional correction data via an internet connection. The NTRIP configuration is made via a Wi-Fi access point and the front screen will display status and connection information.
Figure 1: Racelogic VBOX NTRIP modem
Interfacing
The circuit diagram in Figure 2 shows how to connect the RTCM connector of the MTi-680G to the Racelogic NTRIP modem.
This setup can be realized by using the CA-MP4-MTi cable. The wire map for this cable can be found in the MTi-600-Series Development Kit User Manual.
The pin description of the Racelogic NTRIP modem connector can be found in the Racelogic VBOX NTRIP modem User Guide.
The Racelogic NTRIP modem is using the main connector to output the RTCM messages. This connector must be connected to the RTCM correction port of the MTi-680G.
Figure 2: MTi-680G and Racelogic NTRIP modem connection
Please note the following power supply remark for the Racelogic NTRIP modem:
There are two ways for the Racelogic NTRIP modem to connect to an NTRIP server, namely via:
- Wi-Fi network: You can power the Racelogic NTRIP modem using a USB cable. This is applicable only if you want to use the Racelogic modem with a Wi-Fi network.
- 4G Modem (using SIM card): If you want to use the 4G Modem function then you will need to connect the Racelogic modem to an external 12V DC (7 – 30V) power supply. The 4G Modem is disabled if you are powering the device via USB. The RTCM connector of the MTi-680G does not offer a power supply; you will have to connect the Racelogic NTRIP Modem connector to an external power supply.
Configuration
Start by configuring the MTi-680(G) RTCM port baud-rate settings and output configuration.
- The easiest way to do this is by using our GUI, MT Manager, which is part of the MT Software Suite.
- In MT Manager, open the Device Settings window (
). - In the Device Settings Tab, set the RTCM port baudrate to 115200. Click Apply.
- In the Output Configuration tab, make sure the Status Word, Position and Velocity outputs are enabled, this will help us later check the RTK status fix. Choose a high-resolution output format, such as Fixed Point 16.32 or Float 64-bit. Click Apply.
Once the MTi-680(G) is configured follow the instructions in the Racelogic NTRIP Modem Quick Guide to connect to an NTRIP client and start outputting RTK corrections.
Once the configuration is complete, the Racelogic NTRIP modem should be connected to an NTRIP client and receive-output RTK corrections:
Figure 3: RTK fix indication of Racelogic NTRIP modem
Once that is implemented, the received RTCM messages are forwarded to MTi-680(G).
After launching MT Manager, you should be able to confirm an RTK Float/Fix using the StatusWord message or the RTK Status flag:
- Status Word: Open the Device Data view (
) to view Status Word message.
The 5th bit from the left indicates RTK Float, the 4th and 5th bit from the left together indicate an RTK fix. More information regarding the contents of Status Word message can be found in the Low Level Communication Protocol Documentation.
Figure 4: StatusWord message in the Device Data View
- RTK Status flag: Open the Status Data window (
) to view the status of the RTK flag
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Figure 5: RTK high(fix) in Status Data window
Interfacing the Racelogic NTRIP modem with the MTi-680 Development Kit
The MTi-680-DK comes with an external RTK GNSS daughter card. In this case you can feed the Racelogic NTRIP modem RTCM corrections directly to the RTK GNSS daughter card.
The Racelogic NTRIP modem RTCM outputs must be connected to the XBee socket of the external MTi-680 DK RTK GNSS daughter card. The XBee socket pinning can be found in the MTi-600-Series Development Kit User Manual.
Troubleshooting
- I am connected to an NTRIP client but I can not get an RTK fix with the Racelogic NTRIP modem:
If you are powering the NTRIP modem via USB make sure you are using a high quality USB cable
If the problem persists power the NTRIP modem via an external power supply
Make sure you have an active internet connection (via Wi-Fi or GSM)
Make sure the antenna of the NTRIP modem has a clear view of the sky
Ensure that the NTRIP server you are connected to is not using base stations which are far away (>25 km) from your location, try another mount point or another NTRIP server
- The Racelogic NTRIP modem reports an RTK fix but the MTi-680(G) RTK flag shows a float/low status
Check the baudrate RTCM port settings of MTi-680(G); the baudrate should be set to 115200
The GNSS antenna of the MTi-680(G) should have a clear view of the sky and the MTi-680(G) should report a GNSS Fix (GNSS flag high)