Optical modem troubleshooting

As an alternative to the RBR mooring line modem (“MLM”) RBR offers a variant of the RBRcervello that uses an optical modem to communicate with the instrument mounted on the mooring line. This consists of a head-end optical modem (“HEOM”) that is coupled to the buoy-mounted RBRcervello, and a sub-surface optical modem (“SSOM”) coupled onto the instrument.

Power-on indication

The SSOM will flash once when powered on.

The HEOM will begin flashing at 1-second intervals when powered on.

Optical modem baud rate

The instrument needs to be configured to communicate at the baud rate as configured in the SSOM, which is typically 115200 bits-per-second. The RBRcervello and the HEOM are also pre-configured to communicate at 115200 bits-per-second.

Opening an interactive communication session

As with the RBR MLM, the optical modems can be troubleshooted using transparent-link command

With the HEOM connected to the RBRcervello’s optical modem port and the SSOM connected to an instrument’s optical modem port:

1. Place the optical modems within 1m of each other, with their transmitter/receiver sides aligned within a 240-degree cone. As the LEDs are very bright, it is recommended that the modems be placed on the bench surface with their transmitter/receivers facing down and that the pair be covered.

2. Ensure that the instrument is receiving power. When the instrument begins receiving power, the SSOM will flash once.

3. Issue the status command.

4. If the RBRcervello’s status is not already disabled, issue the disable command.

5. Issue the transparent-link command.

6. If the HEOM is not already powered on, indicated by flashing at approximately 1s intervals, the text “Onboard parameters initialised. �3�set DEBUGLEVEL to6�?“ should appear in the RBRcervello’s terminal after “Connected. Press CTRL-C to exit when done.", and the HEOM should begin flashing at approximately 1s intervals.

7. Tap the ENTER key. The HEOM should flash as it transmits the incoming data.

8. Issue the id command. The HEOM should flash as it transmits the incoming data and the SSOM should flash as it transmits the response. The instrument’s type, version, serial number, and firmware type should appear in the RBRcervello’s terminal

For further troubleshooting, if both the HEOM and the SSOM are receiving power but not exchanging data, an RBR RS-232 patch cable can be used to communicate with either optical modem from a PC running a terminal emulator at 115200 baud.