Twinleaf Sensor Interconnect

There are several communication adapters and data transports used with Twinleaf sensor data:

• RS422
  • Twinleaf Differential Serial (TDS).
  • Supports long cable lengths up to 1 km.
  • Four twisted pair wire, like CAT5/6.
  • Communication adapter name: COMM-TDS.
• Ethernet
  • Protocol: UDP (RFC 768).
  • Power: Power over ethernet (IEEE 802.3af).
  • Synchronization: Precision Time Protocol (IEEE 1588-2008) (Planned for Q3 2025)
  • Only two twisted pairs required.
  • Communication adapter name: COMM-ETH.
• USB Serial
  • USB-C ports and cables.
  • USB CDC Profile (virtual serial port).
  • Communication adapter name: COMM-USB.
• TTL Serial
  • Twinleaf TTL Serial (TTS).
  • The native sensor link used for very short internal connections to communication adapters and certain synchronization units.
  • Seven single wires.
  • No adapter required.

Each of the first three protocols is implemented by a communication adapter that can be specified and installed inside the sensor. The TDS sensor link is commonly used for sensors designed to operate in the field. The USB adapter is commonly used for devices designed for office or laboratory use. A different communication adapter can be specified at the time of order. The TTS link is the "native" link used by sensors and does not employ any additional module. TTS is only offered to system integrators who are specifically trained in its use. This diversity of options reflects the variety of applications for our sensors. Before placing an order, we strong recommand sending us an email us describing your application to obtain a suggested configuration.

All of the communications adapters includes an accelerometer, gyroscope, barometric pressure, and temperature.

Synchronization

There are several options for synchronizing sensors with each other and/or with an external timebase.

• SYNC8-TDS
  • Supports 8 channels RS422/TDS cables
  • GPS or external PPS synchronization
• SYNC8-TTS
  • Supports 8 channels serial/TTS links
  • GPS or external PPS synchronization
• SYNC3-TTS
  • Supports 3 cannels serial/TTS links
  • External PPS synchronization

All communication modules (COMM-USB, COMM-TDS, COMM-ETH) also accept an external 1PPS timepulse to discipline their local oscillator.

Routing

A typical system routes data through one or more hubs before reaching the sensor. For example, the standard VMR sensor system might contain two hubs connected as follows:

• Host computer
  • USB cable
• routing /: USB-TDS: A USB-serial adapter for TDS/RS422 cables
  • CAT5/6 cable (potentially rather long)
• routing /0: COMM-TDS: The TDS/RS422 communication adapter inside the sensor
  • short, internal serial TTS link
• routing /0/0: VMR: A vector magnetometer

At each hub, the twinleaf protocol uses a routing byte to indicate which port the data should pass through. The vector magnetometer data will emerge with the /0/0 route appended to it and the IMU data from the communication adapter would be reported at the /0 route. To communicate directly with the magnetometer in this configuration, routing of "/0/0" should be specified. It is possible to specify the routing subtree at the proxy using:

tio-proxy /dev/ttyACM0 -s /0/0

Note that the pre-2025 legacy SSD connection is closely related to the TDS standard. For short (few meter) cable lengths, devices having SSD ports can connect to TDS host ports without synchronization. The TDS links support very long cable lengths.