100BaseT1 "2-Wire" Ethernet
100BaseT1 Ethernet interface
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.
| Name | Color | Function |
|---|---|---|
LED1 | Orange | TMS/GPIO0/CFG0 |
LED2 | Green | TDI/GPIO1 |
<TODO - additional description during operation>
T1 Ethernet Schematics
At the time of publication (1/16/2023) TJA1103 pinout information was not allowed to be made public. It is expected this is a very short term restriction.
Datasheets and technical documents for TJA1103 are available on request for users with an NXP account.
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