U.S. patent application number 15/016710 was filed with the patent office on 2017-08-10 for system for transmitting control signals over twisted pair cabling using common mode of transformer.
The applicant listed for this patent is ADVOLI Limited. Invention is credited to Clas Gerhard Sivertsen.
Application Number | 20170230204 15/016710 |
Document ID | / |
Family ID | 59410779 |
Filed Date | 2017-08-10 |
United States Patent
Application |
20170230204 |
Kind Code |
A1 |
Sivertsen; Clas Gerhard |
August 10, 2017 |
SYSTEM FOR TRANSMITTING CONTROL SIGNALS OVER TWISTED PAIR CABLING
USING COMMON MODE OF TRANSFORMER
Abstract
A system for transmitting control systems over twisted pair
cabling. The system includes a first microcontroller transmitting a
first single ended signal and receiving a second single ended
signal. It also includes a first differential transmitter coupled
to the first microcontroller for receiving the first single ended
signal from the first microcontroller and converting it to a
differential signal over a first differential line and a second
differential line; and, a first differential receiver coupled to
the first microcontroller for receiving a third differential line
and a fourth differential line and converting it to a differential
receiver signal, the differential receiver signal coupled to the
second single ended signal. The system has a first transformer
having first, second, third, and fourth center-tapped coils, the
first differential line coupled to the center tap of the first
coil, the second differential line coupled to the center tap of the
fourth coil, the third differential line coupled to the center tap
of the second coil, and the fourth differential line coupled to the
center tap of the third coil, whereby the common mode of the first
transformer is used to transmit a first control signal and to
receive control signal responses over the twisted pair at the first
processor.
Inventors: |
Sivertsen; Clas Gerhard;
(LILBURN, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ADVOLI Limited |
Taipei |
|
TW |
|
|
Family ID: |
59410779 |
Appl. No.: |
15/016710 |
Filed: |
February 5, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 25/0276 20130101;
H03F 3/195 20130101; H04L 5/20 20130101; H04N 7/10 20130101; H04L
25/0292 20130101; H04B 3/56 20130101; H04N 7/108 20130101; H04L
25/028 20130101; Y10T 29/4902 20150115; H04L 25/0282 20130101; H04L
25/0266 20130101 |
International
Class: |
H04L 25/02 20060101
H04L025/02; H04B 3/56 20060101 H04B003/56 |
Claims
1. A system for transmitting control signals over twisted pair
cabling, comprising: a first processor transmitting a first single
ended signal and receiving a second single ended signal; a first
differential transmitter coupled to the first processor, the first
differential transmitter receiving the first single ended signal
from the first processor and converting it to a differential signal
over a first differential line and a second differential line; a
first differential receiver coupled to the first processor, the
first differential receiver receiving a third differential line and
a fourth differential line and converting a second differential
signal received over the third differential line and the fourth
differential line to a differential receiver signal, the
differential receiver signal coupled to the second single ended
signal; and a first transformer having first, second, third, and
fourth center-tapped coils, the first differential line coupled to
the center tap of the first coil, the second differential line
coupled to the center tap of the fourth coil, the third
differential line coupled to the center tap of the second coil, and
the fourth differential line coupled to the center tap of the third
coil, whereby the common mode of the first transformer is used to
transmit a first control signal and to receive control signal
responses over the twisted pair at the first processor.
2. The system of claim 1, further comprising: a second transformer
coupled to the first transformer; and a power supply, the positive
side of the power supply coupled to the center tap of the first
coil of the first transformer and the negative side of the power
supply coupled to the center tap of the second coil of the
transformer, whereby power is transmitted from via the first
transformer to the second transformer.
3. The system of claim 2, further comprising: a first isolation
capacitor coupled between the third differential line and the
center tap of the second coil; and a second isolation capacitor
coupled between the fourth differential line and the center tap of
the third coil.
4. The system of claim 3, further comprising: a first pull-up
resistor having a first end coupled to a node between the first
isolation capacitor and the first differential receiver and a
second end coupled to a positive voltage source; a second resistor
having a first end coupled to the node between the first isolation
capacitor and the first differential receiver and a second end
coupled to a node between the second isolation capacitor and the
first differential receiver; and a third resistor having a first
end coupled to the node between the second isolation capacitor and
the first differential receive and a second end coupled to
ground.
5. (canceled)
6. The system of claim 2, wherein the second transformer comprises
a first, second, third, and fourth center tapped coils and wherein
the ends of the respective coils of the first transformer and the
second transformer are coupled to each other via, respectively,
four twisted pairs of wires.
7. The system of claim 6, further comprising a direct current to
direct current isolation converter have first and second inputs and
an output of a first voltage and ground, the first input of the
converter coupled to the center tap of the first coil of the second
transformer and the second input coupled to the center tap of the
second coil of the second transformer, whereby power is received at
the second transformer from the first transformer.
8. The system of claim 7, further comprising: a second processor
transmitting a third single ended signal and receiving a fourth
single ended signal; a second differential transmitter coupled to
the second processor for receiving the third single ended signal
from the second processor and converting it to a differential
signal over a fifth differential line and a sixth differential
line; and a second differential receiver coupled to the second
processor for receiving a seventh differential line and an eighth
differential line and converting a third differential signal
received over the seventh differential line and the eighth
differential line to a second differential receiver signal, the
second differential receiver signal coupled to the fourth single
ended signal, wherein fifth differential line is coupled to the
center tap of the second coil of the second transformer, the sixth
differential line is coupled to the center tap of the third coil of
the second transformer and the seventh differential line is coupled
to the center tap of the first coil of the second transformer, and
the eight differential line is coupled to the center tap of the
fourth coil of the second transformer.
9. A system for transmitting control signals over twisted pair
wires, comprising: a processor having a single-ended transmission
signal and a single-ended reception signal; a converter coupled to
the processor for converting the single ended transmission signal
to a differential transmission signal and for converting a
differential reception signal into the single-ended reception
signal; and a transformer comprising at least four coils, having a
first set of coils and a second set of coils, with a first set of
coils having their respective center taps coupled to the
differential transmission signal and a second set of coils having
their center taps coupled to the differential reception signal,
wherein the four coils of the transformer are respectively coupled
to a first end of four twisted pairs.
10. The system of claim 9, further comprising a power supply
coupled to the center taps of one of the coils in the first set of
coils and to one of the coils in the second set of coils.
11. The system of claim 9, further comprising an isolator between
the differential reception signal and the converter.
12. The system of claim 10, further comprising: a second
transformer having a first set of coils and a second set of coils
respectively coupled to a second end of the four twisted pairs.
13. The system of claim 12, further comprising a direct current to
direct current isolation circuit coupled to center taps of the
first set of coils in the second transformer to receive power from
the power supply via the twisted pairs.
14. The system of claim 13 further comprising: a second processor
having a second single ended transmission signal and a second
single ended reception signal; a second converter coupled to the
second processor for converting the second single ended
transmission signal to a second differential transmission signal
and for converting a second differential reception signal into the
second single-ended reception signal, wherein the second
differential reception signal is coupled to the center taps of the
first set of coils and the second differential transmission signal
is coupled to the center taps of the second set of coils.
15. A method, comprising: receiving a first single-ended
transmission signal; converting the single-ended transmission
signal to a differential transmission signal; transmitting the
differential transmission signal over a first two twisted pairs of
wires via a common mode of a transformer; receiving a differential
reception signal over a second two twisted pairs of wires via the
common mode of the transformer; and converting the differential
reception signal to a single-ended reception signal; transmitting
power over the common mode of the transformer via the four twisted
pairs; transmitting a second single-ended transmission signal; and
converting the second single-ended transmission signal into the
differential reception signal.
16. (canceled)
17. The method of claim 15, further comprising: receiving the
differential transmission signal from the first two pairs of wires
using a second transformer; and converting the differential
transmission signal into a single ended transmission signal.
18. (canceled)
Description
BACKGROUND
[0001] Ethernet has become a widespread method of transmitting
information over local area networks. Ethernet is a common term
used to describe the link layer and physical layer standards of
communication. At the physical layer, Ethernet often communicates
over twisted pair cabling using the various 10-BaseT, 100-BaseT,
1000BaseT, or 10GBaseT standards. Ethernet may also be transmitted
using the HDBaseT standard and twisted pair cabling. HDBaseT is
also able to transmit audio and video signals, as well as power and
usb signals over traditional twisted pair cabling, typically Cat5e
or Cat6 cabling. However, transmission of control signals
traditionally requires an additional cable. This causes problems
were one cable breaks and the other remains: for example, the
control cable breaks, but the video cable remains. Using multiple
types of cables causes problems in installations with multiple
channels, where the cable carrying the control signal may be
mistakenly associated with the wrong Ethernet cable.
[0002] Even where prior art communications systems communicate both
video and control signals over the same cable, such systems, such
as HDBaseT systems powered by Valens chips, require that both the
receiving and the transmitting system be fully up and running.
Thus, in a display system using HDBaseT to communicate between a
computer and a display, both the display and the computer must be
powered on. However, often times the displays are not powered on,
so prior art systems do not enable remote turn on or control of the
display. Leaving both systems constantly powered on in order to
facilitate transmission and reception of control signals is quite
power hungry.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is noted that, in accordance with the standard practice
in the industry, various features are not drawn to scale. In fact,
the dimensions of the various features may be arbitrarily increased
or reduced for clarity of discussion.
[0004] FIG. 1 is a block diagram of an exemplary display system in
accordance with some embodiments.
[0005] FIG. 2 is an electrical drawing of more detailed of the
transmission circuitry in accordance with some embodiments.
DETAILED DESCRIPTION
[0006] The following disclosure provides many different
embodiments, or examples, for implementing different features of
the provided subject matter. Specific examples of components and
arrangements are described below to simplify the present
disclosure. These are, of course, merely examples and are not
intended to be limiting. In addition, the present disclosure may
repeat reference numerals and/or letters in the various examples.
This repetition is for the purpose of simplicity and clarity and
does not in itself dictate a relationship between the various
embodiments and/or configurations discussed.
[0007] This disclosure provides a display system and a method for
transmission of control data over twisted pair cabling, for
example, cabling used in conjunction with HDBaseT communications.
In this detailed description, the term "adapter" refers to either
an external display dongle, an internal dongle, a controller card
in a display, or a daughter card mounted or connected to a
controller card in a display. A graphics card communicates with an
adapter in communication with a display. The graphics card is used
in conjunction with a computer. The graphics card in conjunction
with the adapter provide for control signals to be transmitted by
the computer system to a display via the adapter. Using, for
example, the Consumer Electronics Control ("CEC") protocol, the
host system containing the graphics card may send control signals
to a display in communication with the adapter over a side-band
signal that does not require the display to be powered on. The
control signals are differential signals electrically superimposed
on the communications signals (in HDBaseT, Pulse Amplitude
Modulation ("PAM") signals), acting as a side-band signal. By using
differential signals transmitted across separate pairs, noise and
interference effects on the control signal is minimized.
[0008] FIG. 1 is a block diagram of an exemplary display system in
accordance with some embodiments. As shown in FIG. 1, a display
system 100 is provided. The display system 100 includes a graphics
card 110, a display 160, and a display adapter 140. The graphics
card 110 may be plugged onto a motherboard (not shown) of a PC via,
for example, a PCI Express Interface 111. The graphics card 110 may
include a graphics processing unit ("GPU") 112, a video converter
114, an audio/video ("A/V") transmitter 116, a transformer 118, an
RJ45 connector 120, a memory 122, and a controller 124 connected to
a serial port, such as USB port 126. The GPU 112 is connected to
the video converter 114, for example, a Display Port to HDMI
converter. The GPU 112 provides, for example, video data via
Display Port interface to the video converter 114. Display Port is
a digital display interface developed by the Video Electronics
Standards Association (VESA), and is primarily used to connect a
video source to a computer display, though it can also be used to
carry audio, USB, and other forms of data.
[0009] Alternative embodiments do not include a GPU 112, but rather
receive a Display Port signal at the Display Port to HDMI converter
114 or altogether bypass the Display Port to HDMI converter 114 and
receive an HDMI signal at transmitter 116.
[0010] The output of the video converter 114 is connected to the
audio/video transmitter 116 and to an EDID (EEPROM) 122. The video
converter 114 receives and outputs video data to audio/video
transmitter 116 via HDMI interface. The audio/video transmitter 116
is further connected to the transformer 118 and transmits
audio/video signal. Existing technology examples of an audio/video
transmitters and receivers are: Valens chipsets utilizing HDBaseT
standard and Aptovision BlueRiver chipsets using standard IP based
systems. Those skilled in the art after reading this disclosure
would appreciate that other chip sets with other standards could be
used as the audio video transmitter 116. The audio/video signal may
be HDBaseT. HDBaseT is a consumer electronic and commercial
connectivity standard for transmission of uncompressed
high-definition video, audio, power, home networking, Ethernet,
USB, and some control signals, over a common category (ordinary
Cat5 may be used, but Cat6e or above provides for longer reach)
cable with a standard connector (RJ45). As can be seen, in order to
use the Valens or Aptovision system for control signals, all
systems must be powered up. HDBaseT can be transmitted over
category 6a cables or above up to 100 meter, or even longer, with
8P8C modular connectors of the type commonly used for local area
network connections. The transformer 118 is designed and
manufactured to comply with the appropriate standard, such as
HDBaseT standards.
[0011] The video data from the audio/video transmitter 116 is sent
to a local area network 130, such as Ethernet, by using the RJ45
connector 120. For example, HDBaseT supports the 100 Mbit/s version
of Ethernet over twisted pair known as 100BASE-T. This can provide
Internet access, or enable televisions, stereos, computers and
other devices to communicate with each other and access multimedia
content, including video, pictures and music stored on the local
network.
[0012] The controller 124 is connected to the EDID (EEPROM) 122 and
both sides of the transformer 118. The controller 124 may be a
digital signal processor, a processor, a microprocessor, or a
microcomputer on a chip. In certain embodiments, controller 124 and
controller 148 are low power microprocessors. The controller 124
transmits and receives control information to and from a controller
148 on the communications adapter 140 through side-band
communication. This control information may be transmitted using
the CEC standard over novel differential signals superimposed on
the PAM communications that occurs over the cabling 130. More
detail on this novel electrical circuit is described with respect
to FIG. 2 below. The display 160 in communication with adapter 140
need not be powered on for this control communication to occur.
[0013] The display adapter 140 includes an RJ45 connector 142, a
transformer 144, audio/video receiver 146, and the controller 148.
The transformer 144 is designed and manufactured to comply with the
appropriate standard, such as the HDBaseT standards. The
audio/video receiver 146 receives video data from the audio/video
transmitter 116, by using the RJ45 connector 142 and the local area
network 130.
[0014] The display 160 is connected to the display adapter 140 via
HDMI interface. A memory 162 (such as EEPROM) storing an EDID of
the display 160 is powered by HDMI interface even if the display is
turned off. The controller 148 may be a digital signal processor, a
processor, a microprocessor, or a microcomputer on a chip. The
controller 148 of the display adapter 140 communicates with
controller 124 of graphics card 110 to facilitate the transfer of
control signals between the display 162 and the graphics card
110.
[0015] As the graphics card controller 124 is in communication with
the adapter controller 148, the host computer, via the serial port
126, can effectively issue commands or requests to the display 160.
For example, the controllers 124 and 148 may cooperate to issue
commands to the display 160 using the CEC protocol. Using CEC, the
host computer can issue commands to, for example, turn displays on
or off; adjust contrast or brightness; or adjust color. CEC can
also be used to query information from the displays, such as the
model, serial number, and manufacturing date of the display.
[0016] FIG. 2 is an electrical drawing in more detail of the
transmission circuitry in accordance with some embodiments. This
discloses a single channel. Controller 124 communicates using
single ended UART ("Universal Asynchronous Receiver/Transmitter")
transmitter (TX) and receiver (RX) signals to a UART to RS485
converter 212. The UART to RS485 converter 212 converts, at
differential transmitter 215, the TX from single ended UART signal
to a differential signal on two wires and converts, at differential
receiver 220, incoming RS485 two wire signals to a single UART
signal. By using a two wire signal, there is common mode noise
rejection. Once the signal has been differentialized, it is placed
on the twisted pair cable using the common mode of the transformer
118. In this exemplary figure, the transmit signals are placed on
the center taps of coils A and D, respectively. The received
signals are received from the center taps of coils B and C,
respectively. The outside taps of coils A, B, C, and D contain the
communications signals, for example the HDBaseT PAM signals. This
is done because the power level and ground at the graphics card 110
may be different from the power level and ground at adapter 140.
The transformer 118 and 144 provide galvanic isolation.
[0017] Power supply 235 of +12 volts goes into the center tap of
coil A and the minus side of power supply goes into the center tap
of coil B. Thus, power is transmitted on the common mode of the
transformer. Any voltage could of course be used. The power is
transmitted across the twisted pair cabling to the display side. At
the display side, the power is retrieved from the center taps of
the coils and goes to DC to DC isolation converter 210 providing
power to whatever needs it at the adapter 140 side. The power
supply is tightly held at, for example, 12 volts and varies
slightly with the PAM signal that is carried over the twisted pair.
Thus, power is injected at, for example, 12 volts by the graphics
card 110 and power is extracted by the adapter 140.
[0018] The adapter controller 148 has a similar configuration to
that described in the previous paragraphs. Adapter controller 148
also communicates using UART single ended transmission (TX) and
receiver (RX) UART signals to UART to RS485 converter 222. UART to
RS485 converter 222 converts, at differential transmitter 230, the
TX from single ended UART signals to a differential signal on two
wires and converts, at differential receiver 225, incoming RS485
two wire signals to a single UART signal. By using a two wire
signal, there is common mode noise rejection. Once the signal has
been differentialized, it is placed on the twisted pair cable using
the common mode of transformer 144. In this exemplary figure, the
receive signals are received from the center taps of coils A and D,
respectively. The transmit signals are transmitted from the center
taps of coils B and C, respectively. The outside taps of coils A,
B, C, and D contain the communications signals, for example the
HDBaseT PAM signals.
[0019] Isolation capacitors are used on both sides to isolate the
circuits on each side from the other side. Biasing circuits 240 and
250 provide potential on the otherwise floating receiver
differential circuit. In one exemplary embodiment, each of the
three resistors is 100 kilo ohms.
[0020] Thus, the above system uniquely uses the common mode of the
transformer in order to communicate side-band control signals from
a graphics card to an adapter. These signals are superimposed over
the standard communications signals that are placed on the twisted
pair cabling. By using side-band communications in conjunction with
the power supply system described above, control signals can be
transmitted and received, even if the display system is powered
off. The power on the primary side of the transformers showing 1.8V
maybe be 0V when the system is powered off, but the differential
signals on the secondary transformer side will still work the same.
Also, the power to the common mode of the secondary side of the
transformers showing 12V may be 0V when the system is powered off,
but the differential signals superimposed on these signals will
continue to operate at a different bias level.
[0021] The foregoing outlines features of several embodiments so
that those skilled in the art may better understand the aspects of
the present disclosure. Those skilled in the art should appreciate
that they may readily use the present disclosure as a basis for
designing or modifying other processes and structures for carrying
out the same purposes and/or achieving the same advantages of the
embodiments introduced herein. Those skilled in the art should also
realize that such equivalent constructions do not depart from the
spirit and scope of the present disclosure, and that they may make
various changes, substitutions, and alterations herein without
departing from the spirit and scope of the present disclosure.
* * * * *