Using the J2 Serial connector as access point for Differential corrections

The most common way to feed Differential corrections to an RT unit is to use a radio modem connected to the J3 (15 pins) serial port connector of the User cable.

Up until the v2 RT models, the J3 serial port offered a direct connection to the primary GNSS receiver of the RT, making the J3 the only port that could be used for the reception of Differential corrections.

This has changed with the introduction of the V3 RT models, based on the ADK architecture: There is no direct communication to the GNSS receiver any more, all communications are now managed by the xDEV firmware. This allows more flexibility on the connections side, making it possible to use each serial port with different types of input and output streams.

This means that, while the J3 connector remains the easiest to use and recommended option to connect a radio modem to the RT unit, in cases where the J3 connector should become unavailable (due to hardware fault, for example) it is possible to bypass the issue by using the J2 (9 pins) serial port connector instead. The workaround explained below can only be used with the following, ADK based, OxTS units:

• RT500
• RT1003
• RT3000v3 
• Survey+v3

Required settings:

Hardware configuration:

• Power the radio modem separately (no power on the J2 connector).
• Depending on the type of radio modem utilised, if needed, use a 9-to-15 cable to connect the radio modem to the RS232 (J2) serial port connector. The OxTS cable part number 14C0173C would be the ideal cable for this purpose.

Software configuration:

• Configure the unit as usual to receive Differential corrections in the "Hardware Setup > GNSS Differential Corrections" tab:

• Disable the serial output in the "Interfaces > Serial 1 Output" tab:

• Add the following advanced commands to the configuration of the unit in the "Advanced Tools > Commands" tab:
  • -output_none
  • -serial1_input_mode_diff
  • -serial1_baud9600_8n1 (in case the default baud rate 9600 is being used for the radio modem. If a different baud rate is set on the radio modem, change accordingly).