Signal transmission method for USB interface and apparatus thereof

A signal transmission method for a USB interface and an apparatus thereof are provided. The method includes: receiving a first USB signal sent from a sending terminal, processing the first USB signal into a USB-like signal, and transmitting the USB-like signal via a networking cable; receiving the USB-like signal, processing the USB-like signal into a second USB signal, and sending the second USB signal to a receiving terminal. According to the embodiments of the present invention, the first USB signal is processed into a USB-like signal which is similar to the USB signal, the USB-like signal is transmitted via a networking cable, and the USB-like signal is processed into a second USB signal. The transmission process does not require converting the USB signal into a networking-cable signal which is to be transmitted via a networking cable, thereby avoiding conversion between protocols, and simplifying the entire transmission process.

This application claims the benefit of Chinese patent application No. 201210355946.0 filed on Sep. 11, 2012, and the benefit of Chinese patent application No. 201210591694.1 filed on Dec. 31, 2012. Both applications are incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to the field of CMOS integrated circuit technologies, and in particular to a signal transmission method for a USB interface, and an apparatus thereof.

BACKGROUND OF THE INVENTION

Currently, USB (Universal Serial Bus) is a common interface technology which has a wide range of applications in daily life, e.g., USB flash drive, connecting a mouse or keyboard to a PC, USB removable disk. USB specifications include: USB 1.1, USB 2.0 and USB 3.0. USB 1.1 supports Low Speed (1.5 Mb/s) and Full Speed (12 Mb/s); USB 2.0 supports High Speed (480 Mb/s); and USB 3.0 supports Super Speed (5 Gb/s). Transmission cables for the USB interface are generally short and do not meet the requirements in certain application scenarios. For example, when a USB printer is not in the same place as the host (e.g., a computer) and is connected to the host via a USB transmission cable, the printer cannot work normally if the distance from the host is greater than 5 m. Moreover, in an application where the KVM (keyboard, video and mouse) and the host are not in the same place (for security or other reasons), the user can only operate the host through the KVM, which requires long-distance transmission of the USB signal. In security systems, long-distance transmission is also required for USB cameras.

Therefore, as technology develops, it is desirable to achieve long-distance transmission for the USB interface. Currently, signal transmission for a USB interface with a long transmission cable is achieved by: converting the USB signal into a networking-cable signal; transmitting the networking-cable signal by a networking cable; and converting the networking-cable signal into a USB signal. However, since transmission protocols in USB and networking cables are different, when the conventional method above is used, complex conversions from a USB signal to a networking-cable signal and from the networking-cable signal to a USB signal are required, which makes the signal transmission process cumbersome.

SUMMARY OF THE INVENTION

In view of this, an object of the present invention is to provide a USB signal transmission method with a simple transmission process.

In order to achieve the above object, an embodiment of the present invention provides a signal transmission method for a USB interface, including:

receiving a first USB signal sent from a sending terminal, processing the first USB signal into a USB-like signal, and transmitting the USB-like signal via a networking cable; and

receiving the USB-like signal, processing the USB-like signal into a second USB signal, and sending the second USB signal to a receiving terminal, wherein the USB-like signal is a pair of differential signals that meets a USB transmission protocol, does not meet USB signal electrical specifications, and has a signal swing different from those of the first USB signal and the second USB signal.

Preferably, the transmitting the USB-like signal via a networking cable includes: transmitting the USB-like signal by a pair of wires in the networking cable, with at least one of the rest of wires in the networking cable used for ground.

Preferably, the method further includes: using at least one of the rest of wires in the networking cable for power supply.

Preferably, before the processing the first USB signal into a USB-like signal, the method further includes: obtaining a squelch signal according to the first USB signal; and the transmitting the USB-like signal via a networking cable includes: transmitting the USB-like signal by a first pair of wires in the networking cable, and transmitting the squelch signal by a second pair of wires in the networking cable, with at least one of the rest of wires in the networking cable used for ground.

Preferably, the method further includes:

using at least one of the rest of wires in the networking cable for power supply.

Preferably, the method further includes:

transmitting a control signal by at least one of the rest of wires in the networking cable.

Preferably, the processing the first USB signal into a USB-like signal includes:

abstracting a first clock according to a data edge of the first USB signal;

sampling the first USB signal and the squelch signal according to the first clock to obtain a processed first USB signal and a processed squelch signal, and sending the processed first USB signal and the processed squelch signal;

receiving the processed first USB signal and the processed squelch signal, and sending the processed first USB signal and the processed squelch signal to a first-in first-out (FIFO) unit by using the first clock;

receiving a second clock sent from a phase-locked loop (PLL), the second clock having a frequency different from that of the first clock;

reading the processed first USB signal and the processed squelch signal from the FIFO unit by using the second clock;

sending the processed first USB signal and the processed squelch signal read from the FIFO unit; and

receiving the processed first USB signal and the processed squelch signal read from the FIFO unit, and processing the processed first USB signal and the processed squelch signal read from the FIFO unit into the USB-like signal.

Preferably, before the transmitting the USB-like signal via a networking cable, the method further includes: increasing the amplitude of the USB-like signal at a data edge of the USB-like signal.

Preferably, while receiving the USB-like signal, the method further includes: performing equalization on the USB-like signal.

Accordingly, an embodiment of the present invention provides a signal transmission apparatus for a USB interface, including:

a first processing module, adapted to receive a first USB signal sent from a sending terminal, process the first USB signal into a USB-like signal, and transmit the USB-like signal via a networking cable; and

a second processing module, adapted to receive the USB-like signal, process the USB-like signal into a second USB signal, and send the second USB signal to a receiving terminal, wherein the USB-like signal is a pair of differential signals that meets a USB transmission protocol, does not meet USB signal electrical specifications, and has a signal swing different from those of the first USB signal and the second USB signal.

Preferably, the first processing module is adapted to transmit the USB-like signal by a pair of wires in the networking cable, with at least one of the rest of wires in the networking cable used for ground.

Preferably, the first processing module is further adapted to use at least one of the rest of wires in the networking cable for power supply.

Preferably, the first processing module is further adapted to obtain a squelch signal according to the first USB signal;

the first processing module is adapted to: transmit the USB-like signal by a first pair of wires in the networking cable, and transmit the squelch signal by a second pair of wires in the networking cable, with at least one of the rest of wires in the networking cable used for ground.

Preferably, the first processing module is further adapted to use at least one of the rest of wires in the networking cable for power supply.

Preferably, the first processing module is further adapted to transmit a control signal by at least one of the rest of wires in the networking cable.

Preferably, the first processing module includes:

an extraction unit, adapted to extract a first clock according to a data edge of the first USB signal;

a sampling unit, adapted to sample the first USB signal and the squelch signal according to the first clock to obtain a processed first USB signal and a processed squelch signal, and send the processed first USB signal and the processed squelch signal;

a first receiving unit, adapted to receive the processed first USB signal and the processed squelch signal, and send the processed first USB signal and the processed squelch signal to a FIFO unit by using the first clock;

a second receiving unit, adapted to receive a second clock sent from a PLL, the second clock having a frequency different from that of the first clock;

a reading unit, adapted to read the processed first USB signal and the processed squelch signal from the FIFO unit by using the second clock;

a sending unit, adapted to send the processed first USB signal and the processed squelch signal read from the FIFO unit; and

a third receiving unit, adapted to receive the processed first USB signal and the processed squelch signal read from the FIFO unit, and process the processed first USB signal and the processed squelch signal read from the FIFO unit into the USB-like signal.

Preferably, the first processing module further includes:

an amplitude increasing unit, adapted to increase the amplitude of the USB-like signal at a data edge of the USB-like signal.

Preferably, the second processing module further includes:

an equalization unit, adapted to perform equalization on the USB-like signal.

According to the embodiments of the present invention, the first USB signal is processed into the USB-like signal that meets a USB transmission protocol, does not meet USB signal electrical specifications, and has a signal swing different from those of USB signals; the USB-like signal is transmitted via the networking cable; and then the USB-like signal is processed into the second USB signal. The transmission process does not require converting the USB signal into a networking-cable signal, thereby avoiding conversions between the transmission protocols in USB and the networking cable, and simplifying the entire transmission process.

DETAILED DESCRIPTION OF THE INVENTION

The objects, technical solutions and advantages of the embodiments of the present invention will become clearer when read in conjunction with the descriptions below and the accompanying drawings. Clearly, the embodiments described herein are merely some embodiments of the present invention. Any other embodiment obtained by those skilled in the art based on the embodiments described herein without inventive effort falls within the scope of protection of the present invention.

An embodiment of the present invention provides a signal transmission method for a USB interface. A specific embodiment of the signal transmission method is described below in detail.

Embodiment 1 of the present invention provides a signal transmission method for a USB interface.FIG. 1shows a flow chart of the signal transmission method, including the following steps.

Step S101: receiving a first USB signal, processing the first USB signal into a USB-like signal, and transmitting the USB-like signal via a networking cable. Specifically, the first USB signal is sent from a sending terminal. The sending terminal may be a PC HOST, a HUB, etc. The “USB-like signal” in this embodiment of the present invention is a pair of differential signals that meets a USB transmission protocol, does not meet USB signal electrical specifications, and has a signal swing different from those of the first USB signal and the second USB signal, i.e., the “USB-like signal” is a pair of differential signals that is similar to a USB signal.

In this step, the first USB signal is converted into the USB-like signal which is similar to the USB signal, eliminating the need to convert the first USB signal into a networking-cable signal. The USB-like signal can be transmitted via a networking cable, e.g., CAT5e, CAT6.

Step S102: receiving the USB-like signal, converting the USB-like signal into a second USB signal, and sending the second USB signal to a receiving terminal (DEVICE end).

After the transmission by step S101and step S102, ideally, there is no signal loss, i.e., the first USB signal and the second USB signal are the same. However, under normal circumstances, some synchronization signal in the data packets may be lost after the transmission, which does not affect normal transmission of the USB signal, i.e., the first USB signal and the second USB signal are different. The “first USB signal” and the “second USB signal” in the embodiment of the present invention may include both cases, i.e., the “first USB signal” and the “second USB signal” in the embodiment of the present invention may be the same or may be different. But they both are USB signals, and meet a USB transmission protocol and USB signal electrical specifications.

Accordingly, Embodiment 1 of the present invention also provides a signal transmission apparatus for a USB interface.FIG. 2shows a structural diagram of the signal transmission apparatus, including: a first sending/receiving module201, a first processing module202, a second processing module203, and a second sending/receiving module204.

The first sending/receiving module201is adapted to send a first USB signal. The first sending/receiving module201may be a USB interface on a PC or server (HOST).

The first processing module202is adapted to receive the first USB signal sent from the first sending/receiving unit201, process the first USB signal into a USB-like signal, and transmit the USB-like signal to the second processing module203via a networking cable. The first processing module202may be an extender chip repeater.

The second processing module203is adapted to receive the USB-like signal sent from the first processing module202, process the USB-like signal into a second USB signal, and send the second USB signal to the second sending/receiving module204. That is, the transmission between the sending/receiving unit201and the first processing module202is by a USB cable, the transmission between the first processing module202and the second processing module203is by a networking cable, and the transmission between the second processing module203and the second sending/receiving unit204is by a USB cable. The second processing module203may also be an extender chip.

The second sending/receiving module204is adapted to receive the second USB signal sent from the second processing module203. The second sending/receiving module204may be a USB interface on a device (DEVICE), e.g., a USB interface on a USB flash drive, mouse, keyboard, etc. Specifically, the first processing module202may include:

a first receiving unit2021, adapted to receive the first USB signal sent from the first sending/receiving module201;

a first processing unit2022, adapted to process the first USB signal received by the first receiving unit2021into a USB-like signal that meets a USB transmission protocol, does not meet USB signal electrical specifications, and has a signal swing different from those of the first USB signal and the second USB signal; and

a first sending unit2023, adapted to send, via a networking cable, the USB-like signal produced by the first processing unit2022.

The second processing module203may include:

a second receiving unit2031, adapted to receive the USB-like signal sent from the first sending unit2023in the first processing module202;

a second processing unit2032, adapted to process the USB-like signal received by the second receiving unit2031into a second USB signal; and

a second sending unit2033, adapted to send the second USB signal produced by the second processing unit2032to the second sending/receiving module204.

It is noted that the above units may exist independently, or two or more of them may be combined to form a component. Any apparatus that can carry out the functions of the above units falls within the scope of protection of the present invention.

FIG. 3is a structural diagram illustrating a signal transmission apparatus according to an example of Embodiment 1 of the present invention. Specifically, the first USB interface301may be a USB interface on a computer (HOST), the second USB interface304may be a USB interface on a USB flash drive or removable disk (DEVICE), the chip302may be an extender chip close to the computer host side, and the chip303may be an extender chip close to the USB flash drive or removable disk side. The chip302and the chip303may be of the same type. That is, the interface between the first USB interface301and the chip302is a USB interface, the interface between the chip303and the second USB interface304is also a USB interface, and the interface between the chip302and the chip303is a networking-cable interface.

The signals transmitted between the first USB interface301and the chip302and between the chip303and the second USB interface304are USB signals, which meet a USB transmission protocol and USB signal electrical specifications, and are transmitted using USB cables. The signal transmitted between the chip302and the chip303is the USB-like signal which is similar to the USB signal. That is, the signal transmitted between the chip302and the chip303meets a USB transmission protocol but does not meet USB signal electrical specifications, and is transmitted using a networking cable, i.e., the USB-like signal which is similar to the USB signal is transmitted using a networking cable.

In this case, the chip302may perform the functions of the first receiving unit2021, the first processing unit2022and the first sending unit2023shown inFIG. 2, and the chip303may perform the functions of the second receiving unit2031, the second processing unit2032and the second sending unit2033shown inFIG. 2.

According to the embodiment of the invention, the first USB signal is processed into the USB-like signal that meets a USB transmission protocol, does not meet USB signal electrical specifications, and has a signal swing different from those of USB signals; the USB-like signal is transmitted via the networking cable; and then the USB-like signal is processed into the second USB signal. The transmission process does not require converting the USB signal into a networking-cable signal, thereby avoiding conversions between the transmission protocols in USB and the networking cable, and simplifying the entire transmission process.

It is noted that the signal transmission method for a USB interface according to Embodiment 1 of the present invention is applicable to the cases including Low Speed, Full Speed and High Speed. However, the corresponding signal transmission method and signal transmission apparatus would be different, which will be described in detail hereinafter.

Embodiment 2 of the present invention provides a signal transmission method for a USB interface, which is mainly applicable to Low Speed or Full Speed.

The signal transmission method in Embodiment 2 of the present invention is similar to that in Embodiment 1 of the present invention, except that: the signal transmission method in Embodiment 2 of the present invention transmits the USB-like signal using a pair of wires in the networking cable, with at least one of the rest of wires in the networking cable for ground. Reference is made toFIG. 4, which illustrates the transmission process of a signal transmission apparatus that corresponds to the signal transmission method.

The interface between the first USB interface301and the chip302and the interface between the chip303and the second USB interface304are USB interfaces; the interface between the chip302and the chip303is a networking-cable interface. Therefore, the signals between the first USB interface301and the chip302and the signal between the chip303and the second USB interface304are transmitted using USB cables, and the signal between the chip302and the chip303is transmitted using a networking cable.

The USB cable contains four signal wires, for power supply (VSUPPLY, 5V), ground (GND), and the USB signal (D+ and D−), respectively. The networking cable contains eight wires (four pairs). In Low-Speed or Full-Speed USB signal transmission, a pair of wires (e.g., DP and DM shown inFIG. 4) in the networking cable is used to transmit the USB-like signal, and at least one of the other six wires is used for ground. That is, the Low-Speed or Full-Speed USB signal transmission process in the networking cable may have the following cases:

(1) a pair of wires (e.g., DP and DM) in the networking cable is used to transmit the USB-like signal, a wire in the networking cable is used for power supply, and one or more wires of the rest of wires in the networking cable are used for ground;

(2) a pair of wires (e.g., DP and DM) in the networking cable is used to transmit the USB-like signal, a wire in the networking cable is used for ground, a wire in the networking cable is used for power supply, and the rest of wires in the networking cable are used as control signal wires for controlling components in the chip302or303;

(3) a pair of wires (e.g., DP and DM) in the networking cable is used to transmit the USB-like signal, and the rest of wires in the networking cable are used for ground (as shown inFIG. 4);

Clearly, the signal transmission method in the networking cable is not limited to the above cases (1) to (3). However, in Embodiment 2, it is preferred that: a pair of wires in the networking cable is used to transmit the USB-like signal, and at least one wire in the networking cable is used for ground.

Signals transmitted in the differential wires D+ and D−, which are used for transmitting data, meet USB 2.0 signal electrical specifications. The differential wires DP and DM are used for transmitting USB data, but the signals transmitted in the differential wires DP and DM do not meet USB 2.0 signal electrical specifications.

The signal transmission method for a USB interface in the case of Low Speed or Full Speed is described in detail in conjunction withFIG. 5, including the following steps.

A, a first USB interface301sends a first USB signal, e.g., via a pair of differential wires D+ and D−;

B, a first receiving unit3020in a chip302receives the first USB signal, and transmits the first USB signal to a digital logic processing unit (Core Logic Module)3021;

C, the digital logic processing unit3021in the chip302sends the first USB signal to a first sending unit3022;

D, the first sending unit3022in the chip302processes the received first USB signal into a USB-like signal, and transmits the USB-like signal to a chip303via a networking cable, e.g., via a pair of wires DP and DM in the networking cable;

It can be seen that, the first sending unit3022in the chip302shown inFIG. 5can carry out the functions of the first processing unit2022and the first sending unit2023shown inFIG. 2.

The digital logic processing units3021and3024in this embodiment may be used solely for the sending of data, and data processed by the digital logic processing units3021and3024are full-signal swing data.

E, a first receiving unit3023in a chip303receives the USB-like signal sent from the first sending unit3022in the chip302, and sends the USB-like signal to a digital logic processing unit3024in the chip303;

F, the digital logic processing unit3024in the chip303sends the USB-like signal received by the first receiving unit3023in the chip303to a first sending unit3025in the chip303;

G, the first sending unit3025in the chip303processes the received USB-like signal into a second USB signal, and sends the second USB signal to a second USB interface304, e.g., via a pair of differential wires D+ and D− (ideally, the second USB signal is the same as the first USB signal);

It can be seen that, the first sending unit3025in the chip303shown inFIG. 5can carry out the functions of the second processing unit2032and the second sending unit2033shown inFIG. 2.

It is noted that, the transmission of the USB signal between the first USB interface301and the second USB interface304may be two-way. That is, the USB signal can be transmitted from the first USB interface301to the second USB interface304, as well as from the second USB interface304to the first USB interface301. However, at a given moment, a USB signal between the first USB interface301and the second USB interface304is transmitted in one direction. For a USB signal to be transmitted from the second USB interface304to the first USB interface301, the following steps may be performed:

A′, the second USB interface304sends a second USB signal, e.g., via a pair of differential wires D+ and D−;

B′, the second receiving unit3026in the chip303receives the second USB signal, and sends the second USB signal to the digital logic processing unit3024;

C′, the digital logic processing unit3024in the chip303sends the second USB signal to the second sending unit3027;

D′, the second sending unit3027in the chip303processes the received second USB signals into a USB signal, and transmits the USB-like signal to the chip302via the networking cable, e.g., via a pair of wires (DP and DM) in the networking cable;

E′, the second receiving unit3028in the chip302receives the USB-like signal sent from the second sending unit3027in the chip303;

F′, the digital logic processing unit3021in the chip302sends the USB-like signal received by the second receiving unit3028in the chip302to the second sending unit3029in the chip302;

G′, the second sending unit3029in the chip302processes the received USB-like signal into a first USB signal, and sends the first USB signal to the first USB interface301, e.g., via a pair of differential wires D+ and D− (ideally, the second USB signal is the same as the first USB signal).

As can be seen from the above, the chip302and the chip303shown inFIG. 5are equivalent to the first processing module202and the second processing module203, respectively. In addition, the chip302and the chip303may be of the same type, and can carry out the same function.

The signal transmission process for a USB interface in the case of Low Speed or Full Speed is described above. The signal transmission method for a USB interface according to the embodiment of the present invention is applicable to High Speed.

FIG. 6is a flow chart of a signal transmission method for a USB interface according to Embodiment 3 of the present invention. In conjunction withFIG. 2,FIG. 7,FIG. 8(a) andFIG. 8(b), the signal transmission method includes the following steps.

Step S601: a first sending/receiving module201sends a first USB signal, e.g., via a pair of differential wires D+ and D− in the USB cable shown inFIG. 8(a). In addition, the USB cable may also include a power supply signal wire (VSUPPLY, 5V) and a ground wire (GND). The signals transmitted in the pair of differential wires D+ and D meet USB 2.0 signal electrical specifications.

Step S602: the first receiving unit2021in the first processing module202receives the first USB signal sent from the first sending/receiving module201.

Step S603: the first processing unit2022in the first processing module202processes the first USB signal into a USB-like signal.

Before step S603, the following step may be performed: obtaining a squelch signal according to the first USB signal.

In the embodiment of the present invention, the squelch signal may be obtained from the first USB signal by:

determining the absolute value of the difference between D+ and D− of the first USB signal received by the first receiving unit2021, and outputting “no squelch” (logic “0”) if the absolute value of the difference between D+ and D− is greater than 150 mV; outputting “squelch” (logic “1”) if the absolute value of the difference between D+ and D− is less than 100 mV. In the embodiment of the present invention, the squelch signal may be a pulse signal consisting of logic “0”s and logic “1”s. Specifically, this step may be implemented with a comparator.

It is noted that, step S603may include the following steps.

Step S701: abstracting a first clock according to a data edge of the first USB signal received by the first receiving unit2021in the first processing module202;

Step S702: sampling, according to the first clock, the first USB signal and the squelch signal received by the first receiving unit2021to obtain a processed first USB signal and a processed squelch signal, and sending the processed first USB signal and the processed squelch signal;

Step S703: receiving the processed first USB signal and the processed squelch signal, and sending the processed first USB single and the processed squelch signal by using the first clock to a FIFO unit, which may be arranged in the first processing module202;

Step S704: receiving a second clock sent from a PLL, the second clock having a frequency slightly different from that of the first clock, the PLL being arranged in the first processing module202;

Step S705: reading the processed first USB signal and the processed squelch signal from the FIFO unit by using the second clock;

Step S706: sending the processed first USB signal and the processed squelch signal read from the FIFO unit;

Step S707: receiving the processed first USB signal and the processed squelch signal read from the FIFO unit; and

Step S708: processing the processed first USB signal and the processed squelch signal read from the FIFO unit into the USB-like signal.

Step S701is for clock recovery, and steps S702to S707are for clock and data synchronization (clock and data synchronization here refers to writing data into a FIFO by using the clock recovered by a CDR, and reading the data from the FIFO by using a clock generated by a PLL). For the High-Speed USB signal data transmission, the clock recovered from data and the clock generated by the PLL for sending the data are different in frequency. Therefore, directly sending data by using a clock recovered from the data will result in significant jitter, which is undesirable to subsequent data receiving, clock recovery and data sampling. Accordingly, the clock and data synchronization step before the processing the first USB signal into a USB-like signal in the embodiment of the present invention can prevent data jitter, and is beneficial to subsequent data receiving, clock recovery and data sampling. In addition, the clock and data synchronization step may be implemented with a method known in the art, detailed description of which is omitted here.

Step S604: the first sending unit2023in the first processing module202sends the USB-like signal obtained in the step S603to the second processing module203.

In a specific example, the USB-like signal may be sent to the second processing module203according to the method shown inFIG. 8(a), i.e., a pair of wires (DP and DM) in the networking cable is used to transmit the USB-like signal, a pair of wires (SQP and SQM) in the networking cable is used to transmit the squelch signal, and at least one wire in the networking cable is used for ground. In the embodiment, the signal transmission in the networking cable may have the following cases:

(1) A pair of wires (DP and DM) in the networking cable is used to transmit the USB-like signal, a pair of wires (SQP and SQM) in the networking cable is used to transmit the squelch signal, and the rest of wires in the networking cable are used for ground.

(2) A pair of wires (DP and DM) in the networking cable is used to transmit the USB-like signal, a pair of wires (SQP and SQM) in the networking cable is used to transmit the squelch signal, one or two wires in the networking cable are used for power supply, and the rest of wires in the networking cable are used for ground. In this case, online power delivery can be achieved.

(3) A pair of wires (DP and DM) in the networking cable is used to transmit the USB-like signal, a pair of wires (SQP and SQM) in the networking cable is used to transmit the squelch signal, a wire in the networking cable is used for power supply, a wire in the networking cable is used as a control signal wire, and the rest of wires in the networking cable are used for ground.

Clearly, in addition to the above cases (1) to (3), the embodiment of the present invention may include other cases for the signal transmission in the networking cable, however, it is preferred that: a pair of wires (DP and DM) in the networking cable is used to transmit the USB-like signal, a pair of wires (SQP and SQM) in the networking cable is used to transmit the squelch signal, and at least one of the rest of wires in the networking cable is used for ground.

In the case where the networking cable includes a pair of wires for power supply and a pair of wires for ground, as shown inFIG. 8(b), online power delivery can be achieved for High-Speed USB signal transmission, which is impossible for the conventional signal transmission method where the USB signal is converted into a networking-cable signal according to the protocols. This online power delivery-enabled method can greatly reduce signal transmission costs.

Step S605: the second receiving unit2031in the second processing module203receives the USB-like signal sent from the first sending unit2023in the first processing module202.

Step S606: the second processing unit2032in the second processing module203processes the USB-like signal received by the second receiving unit2031into a second USB signal.

It is noted that, before step S606, the following step may be performed: performing clock and data synchronization on the USB-like signal received by the second receiving unit2031. This clock and data synchronization step is similar to the steps S702to S707, detailed description of which is omitted here.

Step S607: the second sending unit2033in the second processing module203sends the second USB signal produced by the second processing unit2032to the second sending/receiving module204, e.g., according to the method shown inFIG. 8(a), i.e., via a USB cable (which includes a pair of differential wires D+ and D− for transmitting the USB signal, a power supply wire VSUPPLY and a ground wire GND);

Step S608: the second sending/receiving module204receives the second USB signal sent from the second sending unit2033in the second processing module203.

Generally, High-Speed USB signal transmission, especially long-distance High-Speed USB signal transmission, suffers signal attenuation, which will cause the second USB signal to be different from the first USB signal, affecting the performance of High-Speed USB signal transmission. In order to reduce the attenuation in the transmission of High-Speed USB signals and improve the quality of the transmission of High-Speed USB signals, in Embodiment 3 of the present invention, the following one or more steps may be performed after step S603and before step S604.

1) increasing the amplitude of the USB-like signal at a data edge of the USB-like signal produced by the first processing unit2022in the first processing module202. Specifically, the amplitude of the USB-like signal may be increased at the transition of a data edge. This is beneficial to correct reception of the second USB signal by the second sending/receiving module.

2) performing equalization on the USB-like signal received by the first receiving unit2031in the second processing module203. In this step, equalization is performed on the signal that suffers attenuation due to long-distance transmission, thereby increasing high-frequency compensation.

In addition, before step S603, the following step may be performed: determining whether the first USB signal received by the first receiving unit2021in the first processing module202is valid, and performing the subsequent steps if the first USB signal is valid.

The signal transmission method for a USB interface provided by Embodiment 3 of the present invention allows transmission of High-Speed USB signals. The USB signal is converted into a USB-like signal, which is similar to the USB signal; and the USB-like signal is transmitted between the first processing module202and the second processing module203via a networking cable, thereby eliminating the need to convert the USB signal into a networking-cable signal, and simplifying the processing steps.

The signal transmission method for a USB interface provided by Embodiment 3 of the present invention can achieve long-distance (100 m and longer) transmission of High-Speed USB signals. In addition, the signal transmission method for a USB interface according to Embodiment 3 transmits the squelch signal separately in the networking cable, instead of transmitting it together with the USB signal, which enables long-distance (longer than 100 m) transmission.

It is noted that, the first processing module202and the second processing module203in Embodiment 3 of the present invention may include the following structures:

an extraction unit, adapted to extract a first clock according to a data edge of the first USB signal;

a sampling unit, adapted to sample, according to the first clock, the first USB signal and the squelch signal received by the first receiving unit2021to obtain a processed first USB signal and a processed squelch signal, and send the processed first USB signal and the processed squelch signal;

a first receiving unit, adapted to receive the processed first USB signal and the processed squelch signal, and send the processed first USB signal and the processed squelch signal to a FIFO unit by using the first clock;

a second receiving unit, adapted to receive a second clock sent from a PLL, the second clock having a frequency different from that of the first clock;

a reading unit, adapted to read the processed first USB signal and the processed squelch signal from the FIFO unit by using the second clock;

a sending unit, adapted to send the processed first USB signal and the processed squelch signal read from the FIFO unit; and

a third receiving unit, adapted to receive the processed first USB signal and the processed squelch signal read from the FIFO unit, and process the processed first USB signal and the processed squelch signal read from the FIFO unit into a USB-like signal.

The technical solution of Embodiment 3 of the present invention will be described hereinafter in detail with a specific example.FIG. 9shows a signal transmission apparatus for a USB interface in the specific example, and the High-Speed USB signal transmission method for a USB interface is described below.

The process of transmitting a High-Speed USB signal from the first USB interface901to the second USB interface904may include the following steps.

A) the first USB interface901sends a first USB signal to the chip902via the USB cable. Specifically, the first USB signal may be transmitted via a pair of differential wires D+ and D− in the USB cable. Moreover, the USB cable may further include a power supply wire VSUPPLY and a ground wire GND;

B) the first receiving unit9020in the chip902receives the first USB signal, and detects the first USB signal (i.e., determines whether the first USB signal is valid) to obtain a squelch signal;

In the embodiment of the present invention, the squelch signal may be obtained from the first USB signal by:

determining the absolute value of the difference between D+ and D− of the first USB signal received by the first receiving unit9020, and outputting “no squelch” (logic “0”) if the absolute value of the difference between D+ and D− is greater than 150 mV; outputting “squelch” (logic “1”) if the absolute value of the difference between D+ and D− is less than 100 mV. In the embodiment of the present invention, the squelch signal may be a pulse signal consisting of logic “0”s and logic “1”s. Specifically, this step may be implemented with a comparator.

In this step, the first receiving unit9020in the chip902may also process the first USB signal into a single-ended signal with full signal swing.

C) the first receiving unit9020in the chip902sends the valid first USB signal to a Clock and Data Recovery (CDR) unit9021; the CDR9021samples the first USB signal, abstracts a data edge in the first USb signal, abstracts a first clock in the first USB signal according to the data edge, samples according to the first clock the first USB signal (the first USB signal received by the receiving module) and the squelch signal to obtain the processed first USB signal and the processed squelch signal, and sends the processed first USB signal and the processed squelch signal;

D) the digital logic processing unit9022receives the processed first USB signal and the processed squelch signal, and sends the processed first USB signal and the processed squelch signal to a FIFO unit by using the first clock; the digital logic processing unit9022receives a second clock sent from a PLL (not shown in the figure, the PLL may be arranged in the chip902), the second clock having a frequency different from that of the first clock; the processed first USB signal and the processed squelch signal are read from the FIFO unit (not shown in the figure, the FIFO unit may be arranged in the digital logic processing unit9022) by using a second clock; and the processed first USB signal and the processed squelch signal read from the FIFO unit are sent;

When a High-Speed USB signal is transmitted using a USB networking cable, amplitude attenuation may occur to the USB signal, and if the amplitude is reduced to a low level, the squelch signal detected by the USB signal receiving terminal (e.g., the second USB interface904) may not be accurate, and valid data may be wrongly identified as invalid data, thus breaking transmission of the signal. In step D), the amplitude of the USB-like signal is increased before the USB-like signal is transmitted via the networking cable, thereby preventing the amplitude from being reduced to a low level, and ensuring the accuracy of data received by the USB-like signal receiving terminal.

E) the first sending unit9023in the chip902receives the processed squelch signal read from the FIFO unit; the second sending unit9024in the chip902receives the processed first USB signal read from the FIFO unit and processes the first USB signal into a USB-like signal; the first sending unit9023in the chip902sends the squelch signal to the chip903; the second sending unit9024in the chip902sends the USB-like signal (i.e., data) to the chip903. Specifically, the USB-like signal may be transmitted using two pairs of wires (DP and DM, and SQP and SQM) in the networking cables, and the SQP and SQM pair is mainly used to transmit the squelch signal.

Furthermore, an amplitude increasing (pre-emphasis) unit may be added to the second sending unit9024in the chip902. The amplitude increasing unit increases the amplitude of data at the transition of a data edge, which is beneficial to data reception at the receiving terminal for the USB-like signal.

In addition, the High-Speed signal obtained from the digital logic processing unit may be a 4-bit parallel full-swing signal, and the second sending unit9024in the chip902may convert the 4-bit parallel data into serial data and then send it in the form of a USB-like signal.

F) the first receiving unit9030in the chip903receives the squelch signal sent from the first sending unit in the chip902, and the second receiving unit9031in the chip903receives the USB-like signal sent from the second sending unit9024in the chip902;

The first receiving unit9030receives the squelch signal transmitted via a networking cable (e.g., SQP and SQM shown inFIG. 9); and the second receiving unit9031receives the USB-like signal transmitted via the networking cable (e.g., DP and DM shown inFIG. 9).

In addition, after the second receiving unit9031in the chip903receives the USB-like signal sent from the second sending unit9024in the chip902, equalization may be performed on the USB-like signal. Equalization on the signal that suffers attenuation due to long-distance transmission can increase high-frequency compensation and ensure the accuracy of the received signal.

G) the first receiving unit9030and the second receiving unit9031in the chip903send the received squelch signal and the received USB-like signal to the CDR9032for clock and data recovery;

G1) the CDR9032samples the received USB-like signal to abstract a data edge in the USB-like signal, abstracts a third clock from the USB-like data according to the data edge, samples the USB-like signal and the squelch signal according to the third clock to obtain a processed USB-like signal and a processed squelch signal, and sends the processed USB-like signal and the processed squelch signal to the digital logic processing unit9033;

G2) the digital logic processing unit9033receives the processed USB-like signal and the processed squelch signal, and sends the processed USB-like signal and the processed squelch signal to a FIFO unit by using the third clock; the digital logic processing unit9033receives a fourth clock sent from a PLL (not shown in the figure, the PLL may be arranged in the chip903), the fourth clock having a frequency different from that of the third clock, reads the processed USB-like signal and the processed squelch signal from the FIFO unit by using the fourth clock (not shown in the figure, the FIFO unit may be arranged in the digital logic processing unit9033), and sends the processed USB-like signal and the processed squelch signal read from the FIFO unit to the first sending unit9034in the chip903.

When a High-Speed USB signal is transmitted using a USB networking cable, amplitude attenuation may occur to the USB signal, and if the amplitude is reduced to a low level, the squelch signal detected by a squelch detecting module of the USB signal receiving terminal (e.g., the second USB interface904) may not be wrong, and valid data may be wrongly identified as invalid data, thus breaking transmission of the signal. In this step, the amplitude of the USB-like signal is increased before it is transmitted, thereby preventing the amplitude from being reduced to a low level, and ensuring the accuracy of data received by the USB signal receiving terminal.

The first sending unit9034in the chip903receives the squelch signal and the USB-like signal sent from the digital logic processing unit9033, and processes the squelch signal and the USB-like signal into a second USB signal.

I) the first sending unit9034in the chip903transmits the second USB signal to the second USB interface904, using a USB cable in this case;

J) the second USB interface904receives the second USB signal sent from the first sending unit9034in the chip903. This concludes transmission of the High-Speed USB signal.

In this specific example, the squelch signal is extracted from the data to be transmitted separately (i.e., using a pair of differential wires SQP and SQM), and long-distance transmission of the USB signal is achieved in a way where the USB signal and the squelch signal are transmitted simultaneously. According to this transmission method, the squelch signal can be detected correctly by the squelch detecting unit at the USB signal receiving terminal (e.g., the chip903shown inFIG. 9) after the High-Speed USB signal undergoes long-distance transmission, thereby achieving correct determination of the validity of data.

The above steps A) to J) are the case where the USB signal is transmitted from the first USB interface901to the second USB interface904. It is noted that, the USB signal may also be transmitted from the second USB interface904to the first USB interface901, i.e., sequentially through the second USB interface904, the third receiving unit9035in the chip903, the CDR9036in the chip903, the digital logic processing unit9033in the chip903, the second sending unit9037and the third sending unit9038in the chip903, the second receiving unit9025and the third receiving unit9026in the chip902, the CDR9027in the chip902, the digital logic processing unit9022in the chip902, the third sending unit9028in the chip902, and the first USB interface901. The transmission in this case is similar to the steps A) to J), detailed description of which is omitted here.

Preferred embodiments of the present invention are described above. It is noted that, various alternations and modifications can be made by those skilled in the art without deviation from the principle of the present invention, and these alternations and modifications shall fall within the scope of protection of the present invention.