Questions tagged [ethernet]

Questions about the electrical implementation of Ethernet; ask another Stack Exchange for software or protocol questions. Specify the speed as 10/100BASE-T is somewhat different from 1000BASE-T, apart form the speed. Those are copper standards; Ethernet over fiber optical cable is also defined.

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854 views

Ethernet magnetics - PHY side center tap isolation

I am designing a PCB that will use a Microchip KSZ9896C 6-port Gigabit Ethernet Switch. In the datasheet (section 7.2) they state that : "the four transformer center tap pins on the KSZ9896C chip ...
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472 views

Center tap of transformer for Ethernet interface

When you see Ethernet PHY chips' application circuit, you can find out the difference about connecting center tap of transformer. Some PHYs should be connect to the DC power but some don't connect to ...
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771 views

LAN port tester

Is there any way to make a simple LAN port tester that can plug into an ethernet port and check for connectivity. I dont want to use the cable testers as it require both ends of a cable to be plugged ...
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474 views

Are there any special internal Ethernet connectors other than RJ45?

I am working on the board that suppose to have 1 GbE port (10/100/1000BASE-T). Looking at connectors all I seem to find is standard RJ45 connector. However in my design the board itself is not ...
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1k views

RJ45 jack with 8 and 10 pin difference

I need to use the next Ethernet interface design which it's got a RJ45 10 pin, the schematic looks like this: (The RJ45 datasheet is: https://katalog.we-online.de/pbs/datasheet/7499111446.pdf) (PHY ...
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1answer
99 views

Direct connection between two SFP+ cables [closed]

I have been reading a lot about modern fiber networking recently and I have a clarifying semi-hypothetical question: Imagine I have two 3-foot sections of Multi Mode Fiber, and four SFP+ 10G ...
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3answers
884 views

Connecting TVS before or behind Ethernet transformer?

I looked at several designs and recomendations. Why do TVS diodes sometimes connect before and behind transformer? What are the pros and cons of connecting before or behind?
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379 views

Ethernet Interface PCB layout

So based on the responses from this thread: Ethernet Interface PCB layout requirement (if any) I made an Ethernet interface layout the best I possibly could using 2 layers. The circuit is of the ...
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880 views

high speed microcontroller - pc communication

I have a project where I have to sample a 4 bit bus every 100ns continuously for a data logging application (I need very low sampling jitter as well). I have a uC that can go up to 300MHz so speed isn'...
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2answers
340 views

Pushing 50W over PoE?

I'm wondering if it's possible to drive 50W via PoE (cat 6e or cat 7) single cable? I want to power up a quite hungry ARM board, which has power rating of 5V 3A (15W) and a camera, which needs 12V 2....
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2answers
507 views

Powering a 2amp micro-usb device over cat5

There was once a phone in my bathroom, so now there is an LV box with a Cat5 cable in it at the end of a 30ft run. Can I hack something together to power a Google Home Mini with that cable?
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310 views

LAN8710A on STM32

I am working on a project in which I want to have an STM32 running FreeRTOS lwIP. I want to connect it via the MII instead of the RMII configuration. I have studied the datasheet for LAN8710A and I ...
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3answers
635 views

Packet loss on LAN point-to-point

I would like to ask if packet loss in p2p LAN is a normal behavior in LAN. And now in more details: I am connecting PC to target board with TI's chip and LAN9221 controller. I am doing a ping-pong ...
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1answer
323 views

Splitting a cat 6 cable through wire/cable connectors

There's been a cock-up in the internet wiring at a building I'm helping out at (I'm installing the networking there) and the builder has tried to rectify the situation with a solution I have zero ...
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1answer
168 views

Correct Ethernet Jack + Magnetics for 100Base-TX

I've been shopping around for Ethernet jacks for use in a personal project. The part specifically states that it's internal PHYs are 100BASE-TX/10BASE-T/Te IEEE 802.3 I understand the basic ...
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370 views

Ethernet Interface PCB layout requirement (if any)

I am doing Ethernet communication to/from an MCU. I got it working great with an ENC28J60 development module: https://www.digikey.com/product-detail/en/olimex-ltd/ENC28J60-H/1188-1044-ND/3471433 I ...
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153 views

Ethernet Transceiver Chip 100ohms impedance

I've designed a pcb which has a 10/100/1000 Mbps Ethernet Transceiver. It's been already manufactured and I am now testing it. I don't have much experience with electronic design therefore I didn't ...
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412 views

LAN9500AI (USB to Ethernet IC) hang if Ethernet cable removed

I need some help on debugging the issue faced on USB to Ethernet design. I have took reference form LAN9500Ai Development board. Issue:- When Turn on the Power , USB to Ethernet work, and Three LED ...
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1answer
99 views

Circuit design for co-layout the XTAL and CPU clock output

I got a circuit design problem. There is a ethernet switch in my circuit. It is needed 25Mhz crystal input. There are two option, 1). Using external crystal. 2). Using CPU clock output. Its block ...
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1answer
60 views

Firmware update and data exchange using ethernet

I use PIC18F97J60 because its built in ethernet controller to exchange data via lan cable. I want to update the firmware of the mcu using the same controller which means using bootloader for the ...
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1answer
135 views

Off board Ethernet connector

I have to design a PCB board for a project where I need to add Ethernet connectivity (100Mbps) which only will be used during the setup process (it won't be connected all the time). The problem is ...
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1answer
294 views

Detecting disconnected ethernet cable

I want to detect if an ethernet cable has become disconnected using an Arduino. The Arduino will be plugged into a wall, not battery powered. Using a LM358 seemed like the correct fit. I hooked up ...
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1answer
381 views

Isolation Voltage rating of Ethernet Magnetics

I am at the front end of a project that, in part, measures Industrial Voltage levels: 208 Vac through 600 Vac, 3 phase. This device needs wired Ethernet connectivity. I've got lots of options for ...
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1answer
2k views

Which RJ45 pins should I use for power supply?

I'm somewhere in a process of creating mini automation system for hobby use. I've already put CAT 5e cables with RJ-45 connectors in walls. They are somewhere between 5 - 30 meters long. On one side ...
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1answer
178 views

POE power will not interfering on Data travelling on Ethernet , Whats the logic

I was design POE+ circuit , so I read lot of articles on POE(power over Ethernet) IEEE802.af 15.4W on PSE side , For 10/100 base T can use Alternative A method where it use to deliverer power on data ...
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2answers
2k views

Differential Pair Length Matching for DP83848I

I'm looking in the datasheet and layout guide of the DP838481 but I can't seem to find where it talks about length matching for the RX and TX differential pairs. It only mentions length matching for ...
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1answer
95 views

Power over Ethernet identification error?

I have a custom board which is powered by Ethernet and I am using the LT4275B from Linear using the recommended schematic. When I am using a cable with only the data pairs [1-2]&[3-6] ([4-5]&[...
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3answers
291 views

Are RJ45 jack sockets universal regarding CAT-X cables

I've noticed some trade/wholesale websites list CAT-X jack sockets separately as the individual numerical version, i.e., (CAT-3 jack socket). I'm aware CAT is a standard, and RJ45 is the socket ...
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0answers
448 views

Is this a suitable common mode choke?

I've got a system here where I get 12V DC from a laptop charger which is connected to the wall. That 12V gets stepped down to 5V using the TPS56221 buck converter (running this at 500 kHz, with an ...
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2answers
1k views

Using Cat5 for DSL from NID - good idea to double up wires for signal integrity / strength?

I am doing some rewiring of our internal phone lines (almost entirely removal of unused lines). The issues we have run into is the router will every now and then simply not connect from the house to ...
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1answer
522 views

CRC implementation for ethernet

With an example for data with a hexadecimal value of 0xda and a polynomial 0x07, I would find the CRC as follows (using the ...
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1answer
145 views

What is the use of CLK125 on Ethernet PHY?

We are working on a KSZ9031 Ethernet PHY with a Zynq 7020. I don't know where connect the CLK125 signal on a Zynq 7020. What is the use of this signal ? Thanks, Jeff
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156 views

nxp microprocessor ethernet socket coding and sending code [closed]

I have nxp lpc43s50 microprocessor and I made an ethernet connection via lan8710 and at24c02 .I know how to connect at24c02 to my microprocessor pins .However I don't know how to send codes to my ...
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427 views

RJ45 dual LED green and yellow operating

Attached is a small section of USB to Ethernet converter design. RJ 45 Connector has one dual LED (see attached) Green and Yellow, backward connected, and drive via the LAN9500 chip pin27. As per ...
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2answers
85 views

usage of at24c02 eeprom with ethernet module

ı design a altium circuit schematic which consists of lan8720 tranciever rj45 and also at24c02 eeprom .However ı dont know exactly what MAC means and what it does. Why do we use eeprom with ethernet?...
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1answer
105 views

ethernet connection of nxp processor [closed]

ı designed a circuit schematic by using altium designer to ethernet connection of my processor (nxp lpc43s50fet256) ı added a circuit schematic as altium designer file .You can see my complete ...
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1answer
265 views

What to place first: termination or pullup/pulldown?

simulate this circuit – Schematic created using CircuitLab I am routing some ethernet signals that have termination resistors as well as pulldown resistors, my question is that as the signal ...
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1answer
45 views

Lpc 43s50FET256 processor and its connections

ı want to buy a nxp LPC43S50FET256 processor and ı made some research but I dont know whether lpc43s50 has already got bridge connections, ı also dont know for example whether ethernet is already ...
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2answers
451 views

Is it reasonable to use Ethernet or USB to input video into FPGA?

I want to use FPGA to do video processing and I need one video input and one output. The problem is most FPGA boards have one (HDMI or VGA) port and the price significantly rises with the boards which ...
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1answer
211 views

10BASE-T Layout Guidelines

How critical are parameters like trace length matching, differential impedance, vias, etc. when designing a 10BASE-T only application? I know that due to the reduced frequency, there is a larger ...
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68 views

Why is Cat 5 only specified to 100Mhz? [duplicate]

Why is Cat 5 cable only specified up to 100Mhz, if it's to be used for 100BASE-TX, which surely contains frequencies much higher than 100Mhz? Likewise, why is Cat 6A only specified to 500Mhz, but is ...
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1answer
2k views

Differential impedance of LVDS rules and tips?

I'm designing a interface PCB with I/O modules using ethernet. It is my first PCB with high speed communication, which is giving me a lot of worries. In the modules documentation it says that the ...
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1answer
65 views

Ethernet Switch used for CCA to CCA comm without FPGA/Proc for MAC

I'd like to connect Ethernet between devices through magnetics without the FPGA or processor involved. For example, I have several off board (PWB) Ethernet signals coming onto my board and then onto ...
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1answer
109 views

Gigabit Ethernet Coupler Design

I'm doing a PCB design which includes a Gigabit Ethernet 'coupler' - i.e coupling from one CAT 5e cable to another via my PCB (see sketch below) My question is, how careful do I need to be with ...
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1answer
51 views

Chipsets that provides access to baseband bits [closed]

Are there any chipsets for high-speed wired connections like USB3.0, Ethernet or PCIe that provides access to the raw signals being transmitted and received along the wire? Kind of like how a software ...
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1answer
831 views

Beginner PLC: Configure Ethernet/IP Connection

I am really new to PLCs programming, connecting, etc. I received a 1756-L72 with Logix5572 Processor and an EthernetIP card. My goal here is to connect it to my laptop along with another device (a Bar ...
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3answers
147 views

Which interface should be used for communication between processors?

I have two processors (STM and Infineon) on the same board and I have to organize communication between them. Yet I'm using Ethernet to communicate between them, but a startup time of Ethernet after ...
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1answer
108 views

Protecting circuit from railway's high voltage

I am designing a control system which is going to be installed near a functioning railway. The system has many interfaces that are externally connected to different devices, it has Wiegand, RS485, ...
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2answers
2k views

Why does this isolation transformer have another transformer in it?

The isolation transformer I'm looking at: http://www.mouser.com/ds/2/336/HX1188NL-515471.pdf My question is why is it there? Is it not enough to have just the transformer on the left?
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1answer
388 views

SGMII, MDIO and link training

I am reading this document : https://www.nxp.com/webapp/Download?colCode=AN3869 I got this link from NXP support, but I did not get a precise answer to my questiosn and I would like to be sure : The ...