Introduction

100BaseT1 2-Wire Automotive Ethernet provides 100MBPS connections over simple twisted 2 wires for a distance of up to 15 meters. The line signaling on the wire is not directly compatible with traditional 100BaseTX (RJ45) connections, but a physical adapter may be used. Otherwise it is the same as traditional Ethernet.

T1 is lightweight and reduces the cabling weight. The interface also does not require the use of magnetics, so it also saves weight and cost in that regard. Typically you will find T1 Ethernet used on Radar, Cameras, MR-CANHUBK3 and NXP flight controllers for drones.

This interface is compatible with the T1 Adapter for PC or other embedded devices RDDRONE-T1ADAPT and the MR-T1ETH8 network switch for robotics. RDDRONE-FMUK66 and FMURT6 also include T1 Ethernet

T1 Ethernet Locator

J18 is the T1 Ethernet connector and it should not be confused with the similar SE050 Secure-Element NFC connector at the opposite corner of the board. This is a JST-GH 2 pin heade. Technically there is a polarity associated with T1 Ethernet, but the TJA1103 Phy is configured to automatically and transparently swap the polarity as needed. It is still a good idea to attempt to maintain the correct polarity.

NavQPlus uses the TJA1103 T1 Ethernet Phy

TJA1103 is the third-generation product of NXP’s successful family of 100BASE-T1 Automotive Ethernet PHYs. It is perfectly suited to support the rapid expansion of Ethernet to the edge of the network or provide robust connection to domain controllers in the center of the car.

TJA1103 complies with all state-of-the-art conformance test specifications and is designed according to ISO 26262 to meet ASIL B, providing enhanced monitoring and diagnostic features

No magnetics

Unlike traditional Ethernet, a heavy coupling transformer is not used. A small common mode choke and simple passive RC network is used for noise filtering. There is an ESD protection diode used and the communications signals are capacitively coupled. This overall lightweight, small size and cost optimized solution lends itself well to mobile robotics applications.

The Ethernet PHY itself is also extremely small:

T1 Ethernet LEDs

There are two LEDS that connect directly to the TJA1103 PHY.

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T1 Ethernet Schematics

Additional T1 Ethernet boards

The following boards also from the NXP Mobile Robotics team may be helpful when working with 100BaseT1 2-wire Automotive Ethernet. They are an adapter and a network switch. In addition to these baords, you may find other NXP EVKs and 3rd party boards that can also be used. In some cases you may need to adapt the two wire, two pin connector to match your own requrements.

This is a small dongle like board for quickly evaluating T1 Ethernet or to connect a laptop or sensor or companion computer with an RJ45 port into a 100BaseT1 port.