CN111314191A

CN111314191A - Data transmission system and method

Info

Publication number: CN111314191A
Application number: CN202010293910.9A
Authority: CN
Inventors: 不公告发明人
Original assignee: United Huaxin Electronics Co Ltd
Current assignee: United Huaxin Electronics Co Ltd
Priority date: 2020-04-15
Filing date: 2020-04-15
Publication date: 2020-06-19

Abstract

The invention provides a data transmission system and a method, wherein the system comprises: the system comprises at least two pairs of full-duplex high-speed transmission data buses, a pair of arbitration buses and a plurality of communication nodes, wherein the communication nodes are respectively connected in parallel and hung on the data buses and the arbitration buses. The invention can realize the high-speed and real-time communication requirements among a plurality of communication nodes by utilizing the high-speed bus in the multipoint interconnection application occasion, the arbitration bus realizes the automatic decision-making selection of the winner communication node, the temporary use right of the data bus of the winner communication node is granted, the arbitration conflict is reduced, and simultaneously, the wiring is simple, and the transmission efficiency and the reliability are high.

Description

Data transmission system and method

Technical Field

The present invention relates to the field of data processing technologies, and in particular, to a data transmission system and method.

Background

A CAN (Controller Area Network) bus has been widely used in the fields of automobile application, industrial automation, and the like because of its advantages of high reliability, real-time performance, and the like.

The CAN bus only comprises a pair of differential signal lines, adopts serial data transmission and has simple structure; the method supports multi-master communication, namely each node device can actively initiate data communication to other node devices on the network at any time, and the communication sequence is determined according to the priority of the address bit of each node device; when a plurality of node devices simultaneously initiate communication, the avoidance priority with low priority is high. However, the bus rate is limited, and is up to 1Mbps (the communication distance is less than 40 meters), and the data of the CAN bus CAN transmit at most 8 bytes of effective data at a time, which cannot meet the design requirement of large data volume high-speed communication among a plurality of node devices. In addition, when there are many node devices hanging on the bus, communication conflicts easily occur, only one node device is allowed to acquire the ownership of the bus for data transmission by arbitration each time, and other node devices have to wait, which also limits the bus rate.

Disclosure of Invention

The invention aims to provide a data transmission system and a data transmission method, which can realize high-speed and real-time communication requirements among a plurality of communication nodes by using a high-speed transmission bus in a multipoint interconnection application occasion, realize automatic decision-making selection of a winner communication node by an arbitration bus, grant the temporary use right of a data bus of the winner communication node, reduce arbitration conflict, and have the advantages of simple wiring, high transmission efficiency and high reliability.

The technical scheme provided by the invention is as follows:

the present invention provides a data transmission system, comprising:

at least two pairs of full duplex, high rate data buses, all of which transmit in units of data frames;

a pair of arbitration buses, configured to transmit in units of arbitration frames, where the arbitration frames have the same transmission time as the data frames, each arbitration frame includes multiple arbitration time periods, the number of the arbitration time periods is not less than the number of the data buses, and each arbitration time period is used to transmit an identifier of a winning communication node in the time period; the identifier is composed of a number of multilevel symbols;

the communication nodes are respectively connected in parallel and hung on the data buses and the arbitration bus;

the communication node comprises:

the symbol sending module is connected with the arbitration bus and used for sending the self identifier to the arbitration bus so as to participate in data sending right competition;

the data sending module is connected with the data bus and used for sending own data to a target data bus;

the control module is respectively connected with the data sending module, the symbol sending module and the arbitration bus and is used for controlling the symbol sending module to send the identifier of the symbol sending module to the arbitration bus in the current arbitration time period of the current arbitration frame when the data sending requirement of the symbol sending module is detected, comparing the bus voltage on the arbitration bus with the identifier and controlling the continuous sending or the stop sending state of the identifier of the communication node according to the compared feedback result; and the number of the first and second groups,

if the identifier is successfully sent, the communication node is a superior communication node of the arbitration time period, a target data bus is selected, and the data sending module is controlled to send own data to the target data bus in the next data frame;

if the identifier is failed to be sent and the current arbitration time period is not the last arbitration time period of the current arbitration frame, controlling the symbol sending module to resend the identifier to the arbitration bus in the next arbitration time period of the current arbitration time period until the identifier is successfully sent or the last arbitration time period of the current arbitration frame is reached.

Further, the control module includes:

the driving unit is used for translating each symbol of the self identifier into a predefined level value to obtain driving output voltage;

the comparison unit is connected with the driving unit and used for comparing the driving output voltage with the bus voltage;

the conduction control unit is connected with the comparison unit and used for controlling the communication node to be conducted with the arbitration bus and conducting the driving output voltage to the arbitration bus when the driving output voltage is smaller than the bus voltage; controlling the communication node to disconnect from the arbitration bus when the drive output voltage is greater than the bus voltage.

Further, the driving unit includes: digital-to-analog converter, voltage buffer;

the comparison unit includes: a voltage comparator;

the conduction control unit includes: an N-type MOS tube;

the communication node inputs each symbol of the self identifier through a signal input end of the digital-to-analog converter;

the digital-to-analog converter is used for translating each symbol into a digital signal with a predefined level value;

the signal input end of the voltage buffer is connected with the signal output end of the digital-to-analog converter, and the signal output end of the voltage buffer is connected with the inverting input end of the voltage comparator and the source stage of the N-type MOS tube and used for amplifying the digital signal;

the non-inverting input end of the voltage comparator is connected with the drain electrode of the N-type MOS tube, and the drain electrode of the N-type MOS tube is connected with the arbitration bus;

if the driving output voltage is smaller than the bus voltage, the N-type MOS tube is conducted to control the communication node to be conducted with the arbitration bus and conduct the driving output voltage to the arbitration bus;

and if the driving output voltage is greater than the bus voltage, the N-type MOS tube is closed, and the communication node is controlled to be disconnected from the arbitration bus.

The invention also provides a data transmission method, which comprises the following steps:

when the current arbitration time period of the current arbitration frame has a data transmission requirement, transmitting an identifier of the arbitration frame to an arbitration bus to participate in transmission right competition;

comparing the bus voltage on the arbitration bus with the identifier, and controlling the continuous sending or stop sending state of the identifier of the communication node according to the compared feedback result;

if the communication node is conducted with the arbitration bus, the identifier is successfully sent, the communication node is a superior communication node in the arbitration time period, a target data bus is selected, and own data is sent to the target data bus in the next data frame;

if the communication node is disconnected from the arbitration bus, the identifier is failed to be sent, and the current arbitration time period is not the last arbitration time period of the current arbitration frame, the identifier is sent to the arbitration bus again in the next arbitration time period of the current arbitration time period until the identifier is successfully sent or the last arbitration time period of the current arbitration frame is reached.

Further, the step of comparing the bus voltage on the arbitration bus with the identifier and controlling the continuous sending or the stop sending state of the identifier of the communication node according to the compared feedback result comprises the steps of:

translating each symbol of the self identifier into a predefined level value to obtain a driving output voltage;

comparing the drive output voltage to the bus voltage;

if the driving output voltage is smaller than the bus voltage, controlling the communication node to be conducted with the arbitration bus, and conducting the driving output voltage to the arbitration bus;

and if the driving output voltage is greater than the bus voltage, controlling the communication node to be disconnected from the arbitration bus.

Further, when there is a need for data transmission in the current arbitration period, the communication node sends its identifier to the arbitration bus to participate in the transmission right election, including the steps of:

if all the communication nodes do not send own identifiers to the arbitration bus to participate in the transmission right election in the current arbitration time period, the communication nodes which acquire the right of ownership of the data bus in the previous arbitration time period still have data to be transmitted, and when the idle data bus exists in the current arbitration time period, the data to be transmitted is sent to the target data bus.

Further, if the number of arbitration time periods contained in an arbitration frame is equal to the number of the data buses plus one, the last arbitration time period of the arbitration frame is used for checking whether a waiting communication node exists.

Further, if there is a waiting communication node in the last arbitration period of the current arbitration frame, the self identifier is not sent in the current arbitration frame.

Further, if the current communication node continuously obtains arbitration success in an arbitration period and occupies the data bus to send the data frame, when the number of times of continuously sending the data frame reaches a specified number, the control module of the communication node controls the symbol sending module of the communication node to delay a plurality of arbitration periods, and then the communication node enters a election queue of the data bus usage right in the arbitration period; the number is customized by the system.

The data transmission system and the data transmission method provided by the invention can realize the high-speed and real-time communication requirements among a plurality of communication nodes by using the high-speed transmission bus in the multipoint interconnection application occasion, realize automatic decision-making selection of the winner communication node by the arbitration bus, grant the temporary use right of the data bus of the winner communication node, reduce arbitration conflict, and have simple wiring, high transmission efficiency and high reliability.

Drawings

The above features, technical features, advantages and modes of operation of a data transmission system and method will be further described in the following detailed description of preferred embodiments in a clearly understandable manner, in conjunction with the accompanying drawings.

FIG. 1 is a schematic block diagram of one embodiment of a data transmission system of the present invention;

FIG. 2 is a schematic block diagram of another embodiment of a data transmission system of the present invention;

FIG. 3 is a schematic block diagram of another embodiment of a data transmission system of the present invention;

FIG. 4 is a flow chart of one embodiment of a data transmission method of the present invention;

fig. 5 is a flow chart of another embodiment of the data transmission method of the present invention.

Detailed Description

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will be made with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, other drawings and embodiments can be derived from them without inventive effort.

For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product. In addition, in order to make the drawings concise and understandable, components having the same structure or function in some of the drawings are only schematically illustrated or only labeled. In this document, "one" means not only "only one" but also a case of "more than one".

In one embodiment of the present invention, as shown in fig. 1, a data transmission system includes:

at least two pairs of full duplex and high-speed transmission data buses Dn, wherein all the data buses Dn transmit by taking a data frame as a unit;

a pair of arbitration buses A, which are used for transmitting in units of arbitration frames, wherein the transmission time of the arbitration frames is the same as that of the data frames, each arbitration frame comprises a plurality of arbitration time periods, the number of the arbitration time periods is not less than that of the data buses Dn, and each arbitration time period is used for transmitting the identifier of the winning communication node Cn of the time period; the identifier is composed of a number of multilevel symbols;

specifically, the arbitration information and the data information on the CAN bus not only share one bus but also are arranged in one frame to be transmitted together, and the arbitration information limits the transmission rate of the data information. In order to increase the transmission rate of the data bus Dn, the arbitration bus a is separated from the data bus Dn. Arbitration information, namely identifiers, is sent on an arbitration bus a, data information is sent on a data bus Dn, which may adopt a completely different high-speed channel coding transmission scheme than the arbitration bus a, the data bus Dn has a higher symbol modulation rate to meet high-speed transmission requirements, and the arbitration bus a has a lower symbol modulation rate to ensure arbitration reliability. The data bus Dn starts transmitting data at the beginning of the arbitration frame and stops transmitting data before the end of the arbitration frame. The arbitration frame includes a number of arbitration periods that is not less than the number of data buses Dn.

The data transmission delay caused by the fact that the dominant communication node Cn cannot be decided and selected due to collision is reduced. However, too many data buses Dn increase the manufacturing cost, and in practical applications, an adaptive adjustment compromise between transmission efficiency and manufacturing cost is required.

The invention adopts a structured data block mode to carry out data transmission, the basic transmission unit is a data frame, and the length of the data frame is set to ensure that the time spent on transmitting 1 data frame does not exceed the time interval specified by a system. This prescribed time interval is called an arbitration frame. It is specified that any communication node Cn can only transmit data frames at the beginning of an arbitration frame and stop data transmission before the end of the arbitration frame. The identifier is transmitted according to the arbitration frame on the arbitration bus A, one arbitration frame is transmitted in one arbitration frame, 1 arbitration frame comprises a plurality of arbitration time periods, the arbitration time periods are used for the communication node Cn to send the identifier of the communication node Cn, and the identifier is used for arbitration when the communication node Cn collides. The data bus Dn transmits data in data frames, and the time interval (or arbitration frame or time slot) for transmitting one data frame may be the same as or different from the time interval (or arbitration frame or time slot) for transmitting one arbitration frame. Without simultaneously increasing the complexity of the design. The arbitration frame with the same frame number and the data frame may have the same starting time or a fixed time offset. The data transmission rates of the data bus Dn and the arbitration bus a are different, but the arbitration frame lengths are the same, and the two have a relatively fixed phase difference, typically 0.

Since there are at least 2 pairs of data buses Dn, 1 arbitration frame contains at least 2 arbitration time periods, and a winning communication node Cn is decided from communication nodes Cn having data transmission demands to transmit data. The number of arbitration periods contained in each arbitration frame is not less than the number of data buses Dn, and may be equal to or greater than the number of data buses Dn. If smaller, it is liable to cause waste of the data bus Dn.

The communication nodes Cn are respectively connected in parallel and hung on the data buses Dn and the arbitration bus A;

the communication node Cn includes:

the symbol sending module is connected with the arbitration bus A and used for sending the identifier of the symbol sending module to the arbitration bus A so as to participate in data sending right competition;

the data sending module is connected with the data bus Dn and used for sending own data to a target data bus Dn;

the control module is respectively connected with the data sending module, the symbol sending module and the arbitration bus A and is used for controlling the symbol sending module to send an identifier of the symbol sending module to the arbitration bus A in the current arbitration time period of the current arbitration frame when the data sending requirement of the symbol sending module is detected, comparing the identifier with the bus voltage on the arbitration bus A and controlling the on-off state between the communication node Cn and the arbitration bus A according to the compared feedback result; and the number of the first and second groups,

if the identifier is successfully sent, the communication node Cn selects a target data bus Dn as a superior communication node Cn of the arbitration time period, and controls the data sending module to send own data to the target data bus Dn in the next data frame;

if the sending of the identifier fails and the current arbitration time period is not the last arbitration time period of the current arbitration frame, controlling the symbol sending module to resend the identifier to the arbitration bus A in the next arbitration time period of the current arbitration time period until the sending of the identifier is successful or the last arbitration time period of the current arbitration frame is reached.

Specifically, each communication node Cn has a unique identifier for identifying its own identity, and is composed of one or more multi-level symbols. Each communication node Cn must first transmit its own symbol on the arbitration bus a before transmitting data, an identifier consisting of several symbols. An arbitration frame consists of several arbitration time periods, one arbitration time period can be won by one or more communication nodes Cn. The communication node Cn can transmit data on the data bus Dn only after the current arbitration frame obtains the ownership of the data bus Dn. The arbitration bus A is transmitted according to arbitration frames, one arbitration frame at least comprises one identifier, the time interval for transmitting one arbitration frame is called an arbitration frame, at least 2 arbitration time periods are contained in 1 arbitration frame, the number of the arbitration time periods is more than or equal to the number of the data buses Dn, and the arbitration time periods are used for the communication node Cn to send own identifiers.

For example, the data transmission system includes 1 pair of arbitration buses a and 2 pairs of data buses Dn, the first arbitration frame T1 includes a first arbitration period T11 and a second arbitration period T12, the second arbitration frame T2 includes a first arbitration time T21 and a second arbitration time T22, and both the first arbitration frame T1 and the second arbitration frame T2 allow 2 symbols to be transmitted for arbitration. Based on the above assumption, if a certain communication node Cn has a data transmission requirement, if the current time is within the first arbitration time period T11 of the first arbitration frame T1, the latest arbitration time period to be used can be selected, and data transmission is performed through the idle data bus Dn, that is, the second arbitration time period T12 of the first arbitration frame T1, and data transmission is performed through the idle data bus Dn. The first arbitration period of the next arbitration frame closest to the current arbitration period may also be selected for data transmission over the free data bus Dn, i.e., the first arbitration period T21 of the second arbitration frame T2 for data transmission over the free data bus Dn. The data bus Dn can be more fully utilized by using the former, and the data transmission time is reduced; using the latter is a bit simpler in arbitration management. When the start of the current arbitration period has arrived, the communication node Cn transmits its own symbol bit by bit onto the arbitration bus a.

When the communication node Cn detects that the communication node Cn has a data sending requirement, the communication node Cn sends an identifier of the communication node Cn to the arbitration bus A in the current arbitration time period of the current arbitration frame, compares the bus voltage on the arbitration bus A with the identifier, and controls the on-off state between the communication node Cn and the arbitration bus A according to the compared feedback result. If the communication node Cn is connected with the arbitration bus a, the communication node Cn is convenient to send its own identifier to the arbitration bus a through the control module, and once the communication node Cn successfully sends its own identifier to the arbitration bus a through the symbol sending module, the communication node Cn obtains the sending right of the current arbitration time period of the current arbitration frame, that is, the communication node Cn is the winner communication node Cn. In this way, the winner communication node Cn in an arbitration frame is the winner communication node Cn in the arbitration frame that wins all arbitration periods in the arbitration frame, and the winner communication node Cn has a sending right and can occupy the data transmission right of the idle data bus Dn in the next arbitration frame. Selecting a winner communication node Cn from the plurality of communication nodes Cn, so that the winner communication node Cn performs data transmission in a next arbitration frame;

after the communication node Cn sends a bit symbol, monitoring the bus voltage on the arbitration bus A; when the bus voltage on the arbitration bus A is different from the symbol sent by the communication node Cn, the sending of the symbol is considered to be failed, and the sending of the subsequent symbol in the identifier of the communication node Cn is stopped; when the bus voltage on the arbitration bus A is the same as the bus voltage sent by the communication node Cn, the communication node Cn is indicated to successfully send a symbol, and the communication node Cn continues to send the next symbol in the identifier; when the communication node Cn successfully sends all the symbols in the identifier, the identifier is considered to be successfully sent, and successful election is performed to obtain the sending right.

When a plurality of communication nodes Cn almost simultaneously transmit identifiers, the communication nodes Cn which can successfully transmit all symbols in the identifiers to the arbitration bus A win the competition of the current arbitration frame for the transmission right, and obtain the ownership of the data bus Dn. If there is a free data bus Dn, the communication node Cn selects a free pair of data buses Dn for data transmission while stopping transmission of its own identifier within the arbitration frame.

If part of the communication nodes Cn detect that the sending of the identifier fails and there is an arbitration time period to be used in the arbitration frame, the part of the communication nodes Cn may continue to participate in the subsequent arbitration, and strive to obtain the right of the idle data bus Dn.

Such as: the data transmission system includes 1 pair of arbitration buses a and 2 pairs of data buses Dn, and it is assumed that 3 arbitration periods (a first arbitration period T11, a second arbitration period T12, and a third arbitration period T13) are included in the first arbitration frame T1, i.e., 3 arbitrations are allowed. Based on the foregoing assumption, if the communication node C1 obtains arbitration wins in the first arbitration period T11 and the second arbitration period T12, the communication node C1 obtains data transmission on a pair of idle data buses Dn as the target data bus Dn, while the communication node Cn stops transmitting its own symbol in the third arbitration period T13 in the first arbitration frame T1, i.e., does not participate in the transmission of the 3 rd arbitration period. Since the communication node C1 has already obtained the data transmission opportunity in the arbitration frame, it does not participate in the subsequent contention of the data bus Dn, and can give other communication nodes Cn opportunities to increase fairness. When the starting time of the current arbitration time period arrives, the communication node Cn sends its own symbols to the arbitration bus a bit by bit in sequence.

If the communication node Cn does not obtain arbitration wins for the 1 st arbitration period T11 of the first arbitration frame T1, the communication node Cn may continue to participate in the 2 nd arbitration of the first arbitration frame T1, retransmitting its own symbol for the 1 st arbitration period T12. Arbitration 3 of the first arbitration frame T1 may also be engaged if arbitration 2 fails. If the 2 nd arbitration is successful and the communication node Cn has obtained a data transmission opportunity, the 3 rd arbitration is not participated in.

The communication node Cn which does not compete successfully has the opportunity to participate in arbitration for obtaining the transmission right for multiple times in an arbitration frame, and can continuously transmit the symbol. In the next arbitration frame, all the devices participate in arbitration again, and win the win of the transmission right of the new round of arbitration frame. Because there are multiple pairs of data buses Dn, multiple communication nodes Cn can compete to obtain the ownership of the data buses Dn, i.e., multiple winning communication nodes Cn, in multiple arbitration frames, thereby increasing the data transmission rate.

In each arbitration period of each arbitration frame, the communication node Cn that wins arbitration, i.e., the winning communication node Cn, will obtain the right to transmit the data frame at the next arbitration frame. The data frame includes an identifier of the receiving device for the receiving device to identify and receive.

In another embodiment of the present invention, as shown in fig. 1, 2 and 3, the control module includes:

the conduction control unit is connected with the comparison unit and used for controlling the communication node Cn to be conducted with the arbitration bus A and conducting the driving output voltage to the arbitration bus A when the driving output voltage is smaller than the bus voltage; controlling the communication node Cn to disconnect from the arbitration bus A when the drive output voltage is greater than the bus voltage.

The driving unit includes: digital-to-analog converter, voltage buffer;

the comparison unit includes: a voltage comparator;

the conduction control unit includes: an N-type MOS tube;

the communication node Cn inputs each symbol of the self identifier through a signal input end of the digital-to-analog converter;

the non-inverting input end of the voltage comparator is connected with the drain electrode of the N-type MOS tube, and the drain electrode of the N-type MOS tube is connected with the arbitration bus A;

if the driving output voltage is smaller than the bus voltage, the N-type MOS tube is conducted, the communication node Cn is controlled to be conducted with the arbitration bus A, and the driving output voltage is conducted to the arbitration bus A;

and if the driving output voltage is greater than the bus voltage, the N-type MOS tube is closed, and the communication node Cn is controlled to be disconnected from the arbitration bus A.

Specifically, each communication node Cn has a unique identifier for identifying itself, and the identifier is composed of a plurality of multilevel symbols. Before sending data, each communication node Cn must first send its own identifier on the arbitration bus a, and after the own identifier is successfully sent on the arbitration bus a, the communication node Cn obtains the use permission of the target data bus Dn, and then can send data on the next frame of the target data bus Dn. The arbitration bus A is transmitted according to arbitration frames, one arbitration frame at least comprises 2 arbitration time periods, and the arbitration time periods are used for the communication node Cn to send identifiers. During each arbitration period, the communication node Cn having a data transmission request can transmit each symbol of its own identifier onto the arbitration bus a in bits before not obtaining the data transmission right.

Assuming that for an arbitration bus A with a bus voltage fluctuating between 0V and 7V, it is defined that less than 0.5V is level 0, between 0.5V and 1.5V is level 1, between 1.5V and 2.5V is level 2, between 2.5V and 3.5V is level 3, between 3.5V and 4.5V is level 4, between 4.5V and 5.5V is level 5, between 5.5V and 6.5V is level 6, and above 6.5V is level 7, the voltage pair (1, 2) indicates that the driving voltage on the arbitration bus A is level 1, and the driving voltage on the arbitration line 2 is level 2.

When Vs (drive output voltage) > Vd (bus voltage), that is, the level at the arbitration bus a is lower than the level output by the communication node Cn, the voltage comparator output amplifies a negative signal (i.e., U voltage comparator < 0), which causes Vg (gate voltage) to decrease and Vg < 0, thereby causing Vgs < Vgs (th), thereby causing the MOS transistor to close, thereby causing the communication node Cn to unsuccessfully transmit its own identifier to the arbitration bus a, and not acquiring the win right of the current arbitration period.

When Vs (driving output voltage) < Vd (bus voltage), that is, the level at the arbitration bus a is higher than the level output by the communication node Cn, the voltage comparator output amplifies a positive signal (i.e., U voltage comparator > 0), which causes Vg (gate voltage) to increase, which causes Vgs > Vgs (th), thereby turning on the N-type MOS transistor, and further, the communication node Cn successfully transmits its own identifier to the arbitration bus a, and successfully obtains the win right of the current arbitration period. The voltage comparator outputs an amplified positive signal indicating that this communication node Cn now has a high priority for data transmission using the data bus Dn.

Each symbol of the identifier is a logical number, each symbol being encoded to result in a corresponding voltage pair on the arbitration bus a. Assuming that the voltage pair corresponding to the symbol 1 is (1, 2), when the communication node Cn transmits the symbol 1, the symbol 1 is encoded, the corresponding voltage pair (1, 2) is found according to the mapping table of the symbol-voltage pair, and then the voltage pair is converted into corresponding driving voltages, such as (1v, 2v), by the arbitration interface module, and the driving voltages are conducted to two arbitration lines, that is, the symbol 1 is successfully transmitted to the arbitration bus a. When judging whether the symbol is successfully sent to the arbitration bus A, the communication node Cn inquires actual voltages on two arbitration lines of the arbitration bus A, removes a fixed amplification factor to obtain a voltage pair, and decodes the voltage pair to obtain a corresponding symbol, for example, a symbol 1 is obtained according to the voltage pair (1, 2).

After the communication node Cn sends a bit symbol of the identifier, monitoring the symbol on the arbitration bus A; when the symbol on the arbitration bus A is different from the symbol sent by the communication node Cn, the sending of the identifier is considered to be failed, and the sending of the subsequent symbol of the identifier is stopped; when the symbol on the arbitration bus A is the same as the symbol sent by the communication node Cn, the communication node Cn is indicated to successfully send the symbol with one bit of the identifier, and the next bit of the identifier is sent continuously; the transmission of the identifier is considered successful when the communication node Cn successfully transmits all symbols of the identifier.

When a plurality of communication nodes Cn simultaneously transmit identifiers, the communication node Cn which can correctly transmit the identifiers to the arbitration bus A wins the arbitration of this time, becomes a winning communication node Cn, obtains the right of use of the next data frame of the target data bus Dn, and stops transmitting the identifier of the communication node Cn in the arbitration frame.

If the identifier transmission failure is detected and the current arbitration time period is not the last arbitration time period of the current arbitration frame, the communication node Cn may continue to participate in subsequent arbitration, and continue to transmit the identifier to participate in data transmission right competition when the next arbitration time period of the current arbitration frame arrives, that is, continue to transmit the identifier to obtain the use right of the target data bus Dn when the next arbitration time period becomes the current arbitration time period.

Example (c): the bus structure comprises 1 pair of arbitration buses A and 3 pairs of data buses Dn, each arbitration frame comprises 3 arbitration time periods, the winning communication node Cn of each arbitration time period obtains the data transmission right of the target data bus Dn corresponding to the arbitration time period, for example, the target data bus Dn of the 1 st arbitration time period is the 1 st pair of data bus Dn, the target data bus Dn of the 2 nd arbitration time period is the 2 nd pair of data bus Dn, the target data bus Dn of the 3 rd arbitration time period is the 3 rd pair of data bus Dn, the winning communication node Cn of the 1 st arbitration period of the current arbitration frame obtains transmission of the next data frame of the 1 st data bus Dn, the winning communication node Cn of the 2 nd arbitration period obtains transmission of the next data frame of the 2 nd data bus Dn, and the winning communication node Cn of the 3 rd arbitration period obtains transmission of the next data frame of the 3 rd data bus Dn.

If the communication node Cn wins arbitration in the 1 st arbitration period of the current arbitration frame, the communication node Cn obtains sending data to the next data frame of the data bus Dn in the 1 st arbitration period as the winning communication node Cn in the arbitration period, and meanwhile, the communication node Cn stops sending its identifier in the current arbitration frame continuously, i.e. does not participate in arbitration in the 2 nd and 3 rd arbitration periods of the current arbitration frame. In the arbitration frame, the communication node Cn has obtained the data sending opportunity, and does not participate in the competition of the subsequent data bus Dn, so that the opportunity can be given to other devices, and the fairness can be increased.

If the communication node Cn does not obtain arbitration wins in the 1 st arbitration period of the current arbitration frame, the communication node Cn may continue to participate in the 2 nd arbitration of the current arbitration frame, and resend its own identifier in the 2 nd arbitration period. If the 2 nd arbitration fails, the 3 rd arbitration of the current arbitration frame can also be participated. If the 2 nd arbitration succeeds, the communication node Cn gets to send data on the next data frame of the data bus Dn at the 2 nd, while not participating in the 3 rd arbitration.

Devices that do not contend successfully have multiple arbitration opportunities in one arbitration frame and can continue to transmit identifiers, and once contention succeeds, no identifiers are transmitted in the current arbitration frame for the purpose of giving other devices opportunities. At the next arbitration frame, all devices are again participating in arbitration.

Because a plurality of pairs of data buses Dn exist, a plurality of communication nodes Cn can compete to obtain the use right of the data buses Dn in each arbitration frame, and therefore the transmission rate of the data buses Dn is improved.

In another embodiment of the present invention, as shown in fig. 1 and fig. 4, a data transmission method is based on the data transmission system described in any of the previous embodiments, and includes:

s100, when the current arbitration time period of the current arbitration frame has a data transmission requirement, transmitting an identifier of the self to an arbitration bus A to participate in transmission right competition;

s200, comparing the bus voltage on the arbitration bus A with the identifier, and controlling the on-off state between the communication node Cn and the arbitration bus A according to the compared feedback result;

s300, if the communication node Cn is conducted with the arbitration bus A, the identifier is successfully sent, the communication node Cn is a superior communication node Cn in the arbitration time period, a target data bus Dn is selected, and data of the communication node Cn is sent to the target data bus Dn in the next data frame;

s400, if the communication node Cn is disconnected from the arbitration bus a, the sending of the identifier fails, and the current arbitration time period is not the last arbitration time period of the current arbitration frame, resending the identifier to the arbitration bus a in the next arbitration time period of the current arbitration time period until the sending of the identifier is successful or the last arbitration time period of the current arbitration frame is reached.

In another embodiment of the present invention, as shown in fig. 1, fig. 2, fig. 3 and fig. 5, a data transmission method includes:

s210, translating each symbol of the identifier into a predefined level value to obtain a driving output voltage;

s220 compares the driving output voltage with the bus voltage;

s230, if the driving output voltage is smaller than the bus voltage, controlling the communication node Cn to be connected to the arbitration bus a, and transmitting the driving output voltage to the arbitration bus a;

s240 if the driving output voltage is greater than the bus voltage, controlling the communication node Cn to disconnect from the arbitration bus a;

When Vs (drive output voltage) > Vd (bus voltage), that is, the level at the arbitration bus a is lower than the level output by the communication node Cn, the voltage comparator outputs a power negative signal (i.e., U voltage comparator < 0), which causes Vg (gate voltage) to decrease and Vg < 0, thereby causing Vgs < Vgs (th), thereby causing the MOS transistor to close, thereby causing the communication node Cn to unsuccessfully transmit its own identifier to the arbitration bus a, and not acquiring the win right of the current arbitration period.

When Vs (driving output voltage) < Vd (bus voltage), that is, the level at the arbitration bus a is higher than the level output by the communication node Cn, the voltage comparator outputs a positive power supply signal (i.e., U voltage comparator > 0), which causes Vg (gate voltage) to increase, which causes Vgs > Vgs (th), thereby turning on the N-type MOS transistor, and further, the communication node Cn successfully transmits its own identifier to the arbitration bus a, and successfully obtains the win right of the current arbitration period. The voltage comparator outputs a positive supply signal while indicating that this communication node Cn now has a high priority for data transmission using the data bus Dn.

In general, only one coding mode in the system converts symbols into voltage pairs, each symbol corresponds to a voltage pair one by one, and different symbols correspond to different voltage pairs, but in this embodiment, there are two coding modes, the same symbol can obtain different voltage pairs according to different coding modes, and when the same symbol is continuously transmitted, the same symbol is transmitted by adopting a coding result in a coding mode different from that of the previous symbol, so that the voltage on at least one arbitration line can have large fluctuation, and the transmission end of an old symbol and the transmission start of a new symbol can be easily identified according to the fluctuation. If only one coding mode is adopted, when the same symbols are continuously transmitted, because the coding results transmitted before and after are the same, the voltage on the corresponding arbitration line is not changed, when each communication node Cn receives the symbols on the arbitration bus A, the judgment error of the communication node Cn is easily caused, and the competition of the data transmission right is influenced. The foregoing problems can be avoided by using two encoding schemes.

Based on the foregoing embodiment, if all the communication nodes Cn do not send their own identifiers to the arbitration bus a to participate in the election of the sending right in the current arbitration period, the communication node Cn that has acquired the ownership of the data bus Dn in the previous arbitration period still has data to be sent, and when there is a free data bus Dn in the current arbitration period, the data to be sent is sent to the target data bus Dn;

specifically, the bus structure comprises 1 pair of arbitration buses A and 2 pairs of data buses Dn, and 2 identifier sending times are contained in one arbitration frame, namely 2 identifiers are allowed to be sent in one arbitration frame, and 2 identifier arbitrations are allowed. If a communication node Cn has won at the time of the 1 st identifier transmission and has gained ownership of the 1 st data bus Dn, the transmission of the 2 nd identifier must be stopped. But when the communication node Cn finds that no other communication node Cn initiates identifier arbitration within the 2 nd identifier sending time, but has additional data to send itself, the communication node Cn will automatically obtain the right to send data on the data bus Dn No. 2. The utilization rate of the data bus Dn can be improved through the embodiment, and meanwhile, the data transmission time of the communication node Cn with the data sending requirement is shortened.

Based on the foregoing embodiment, if an arbitration frame contains an arbitration period number equal to the number of data buses Dn plus one, the last arbitration period of the arbitration frame is used to check whether there is a pending communication node Cn queued.

Specifically, the number of arbitration periods contained in the general arbitration frame is equal to the number of data buses Dn, while the number of arbitration periods contained in the arbitration frame in the present embodiment is one more than the number of data buses Dn, and the extra arbitration period, i.e. the last arbitration period, is used to indicate whether there is a pending communication node Cn waiting in line; the waiting communication node Cn has a data transmission request, but cannot obtain the data transmission right because its identifier has a lower priority than other communication nodes Cn. The other arbitration periods are still used to select the winning communication node Cn and obtain the right to use the next data frame of the target data bus Dn. By the identifier transmission situation of the last arbitration period, it can be determined whether or not there is a communication node Cn of low priority waiting for data transmission. In order to avoid that the waiting time of the communication node Cn with low priority is too long, the sending frequency of the identifier of the communication node Cn with high priority, which has obtained the data sending right, is gradually decreased, and when the sending frequency of the identifier of the communication node Cn with high priority drops to or below a preset threshold, for example, the preset threshold is 0, the communication node Cn is not allowed to send the identifier to the arbitration bus a, so that the communication node Cn with low priority, which is queued for waiting, has an opportunity to obtain the data sending right. When the identifier sending frequency of the communication node Cn falls to or below the preset threshold, the identifier sending frequency of the communication node Cn can be restored to the initial value after passing through several arbitration frames, so as to restore the contention of the communication node Cn for the data sending right.

The bus structure comprises 1 pair of arbitration buses A and 2 pairs of data buses Dn, one arbitration frame comprises 3 arbitration time periods, wherein the first two arbitration time periods are used for selecting a winning communication node Cn, the data transmission right of the 1 st pair of data buses Dn and the 2 nd pair of data buses Dn is obtained, and the last arbitration time period is used for indicating whether a waiting pending communication node Cn exists or not. Four communication nodes Cn participate in the competition of the data transmission right, and the identifier priority of each communication node Cn is as follows: communication node C1> communication node C2> communication node C3> communication node C4, the initial values of the identifier transmission frequencies are all 100%. In the 1 st arbitration period, the communication node C1 wins, obtains the 1 st data transmission right to the data bus Dn, and does not transmit the identifier in the current arbitration frame; in the 2 nd arbitration period, the communication node C2 wins, obtains the 2 nd data transmission right to the data bus Dn, and does not transmit the identifier in the current arbitration frame; in the 3 rd arbitration period, the communication node C3 and the communication node C4 transmit identifiers, the arbitration bus a presents the identifier of the communication node C3, a non-default value indicates that there is a waiting communication node Cn, and the communication node C1 and the communication node C2 know that there is a waiting communication node Cn according to the identifier transmission condition of the last arbitration period, and then reduce the transmission frequency of their identifiers, for example, after the communication node C1 and the communication node C2 continuously transmit data frames for several times and find that there is a communication node waiting for data transmission in the 3 rd arbitration period, the communication node C1 and the communication node C2 delay for several overall periods and then participate in the arbitration process of using the data bus right. The specific number of times is customized by the system.

In this embodiment, when there are many communication nodes Cn with data transmission requirements and data bus Dn conflicts seriously, in order to increase fairness, a communication node Cn with a low priority cannot obtain the right of use of the data bus Dn for a long time, and by reducing the transmission frequency of the identifier of the communication node Cn that has successfully obtained the right of transmission, the communication node Cn with a high priority is made to participate in arbitration less, so that the chance that the communication node Cn with a low priority obtains the right of use of the data bus Dn is increased.

Based on the foregoing embodiment, if there is a waiting communication node Cn in the last arbitration period of the current arbitration frame, the self identifier is not sent in the current arbitration frame.

Specifically, when a plurality of communication nodes Cn simultaneously transmit identifiers, the communication node Cn that can correctly transmit an identifier to the arbitration bus a wins arbitration in the current arbitration period, becomes the winning communication node Cn, obtains the right of use of the next data frame of the target data bus Dn, and stops transmitting its own identifier in the arbitration frame.

Based on the foregoing embodiment, if the winning communication node Cn having a data transmission demand gradually decreases the transmission frequency of its own identifier in the current arbitration period of the current arbitration frame, until the ratio of the number of times of transmission stop to the arbitration period reaches the preset threshold, the contention for the data transmission right is resumed.

Specifically, the number of arbitration periods contained in the general arbitration frame is equal to the number of data buses Dn, while the number of arbitration periods contained in the arbitration frame in the present embodiment is one more than the number of data buses Dn, and the extra arbitration period, i.e. the last arbitration period, is used to indicate whether there is a pending communication node Cn waiting in line; the waiting communication node Cn has a data transmission request, but cannot obtain the data transmission right because its identifier has a lower priority than other communication nodes Cn. The other arbitration periods are still used to select the winning communication node Cn and obtain the right to use the next data frame of the target data bus Dn. By the identifier transmission situation of the last arbitration period, it can be determined whether or not there is a communication node Cn of low priority waiting for data transmission. In order to avoid the waiting time of the communication node Cn with low priority being too long, the identifier sending frequency of the communication node Cn with high priority having obtained the data sending right is gradually reduced, for example, the communication node which has obtained the data bus use right in the arbitration period for several times detects that the communication node has the waiting data sending in the last arbitration period, and then participates in the arbitration process of the data bus use right after delaying for several president periods. The specific number of times is customized by the system.

The bus structure comprises 1 pair of arbitration buses A and 2 pairs of data buses Dn, one arbitration frame comprises 3 arbitration time periods, wherein the first two arbitration time periods are used for selecting a winning communication node Cn, the data transmission right of the 1 st pair of data buses Dn and the 2 nd pair of data buses Dn is obtained, and the last arbitration time period is used for indicating whether a waiting pending communication node Cn exists or not. Four communication nodes Cn participate in the competition of the data transmission right, and the identifier priority of each communication node Cn is as follows: communication node C1> communication node C2> communication node C3> communication node C4, the initial values of the identifier transmission frequencies are all 100%. In the 1 st arbitration period, the communication node C1 wins, obtains the 1 st data transmission right to the data bus Dn, and does not transmit the identifier in the current arbitration frame; in the 2 nd arbitration period, the communication node C2 wins, obtains the 2 nd data transmission right to the data bus Dn, and does not transmit the identifier in the current arbitration frame; in the 3 rd arbitration period, the communication node C3 and the communication node C4 transmit identifiers, the arbitration bus a presents the identifier of the communication node C3, a non-default value indicates that there is a waiting communication node Cn, and the communication node C1 and the communication node C2 know that there is a waiting communication node C4 according to the identifier transmission condition of the last arbitration period, and then reduce the transmission frequency of their identifiers, for example, after the communication node C1 and the communication node C2 continuously transmit data frames for several times and find that there is a communication node waiting for data transmission in the 3 rd arbitration period, the communication node C1 and the communication node C2 delay for several presidentation periods and then participate in the arbitration process of the data bus usage right. The specific number of times is customized by the system.

It should be noted that the above embodiments can be freely combined as necessary. The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A data transmission system, comprising:

the communication node comprises:

2. The data transmission system of claim 1, wherein the control module comprises:

3. The data transmission system of claim 2, wherein:

the driving unit includes: digital-to-analog converter, voltage buffer;

the comparison unit includes: a voltage comparator;

the conduction control unit includes: an N-type MOS tube;

4. A data transmission method, characterized in that the data transmission system according to claim 1 is applied, comprising the steps of:

5. The data transmission method according to claim 4, wherein the step of comparing the identifier with the bus voltage on the arbitration bus and controlling the continuous transmission or stop transmission state of the identifier of the communication node according to the feedback result after the comparison comprises the steps of:

comparing the drive output voltage to the bus voltage;

6. The data transmission method according to claim 4, wherein the communication node sends its identifier to the arbitration bus to participate in the right-to-send election before the communication node sends its identifier to the arbitration bus to participate in the right-to-send election when there is a need for sending data in the current arbitration period, the method comprising the steps of:

7. The data transmission method according to any one of claims 4 to 6, characterized in that:

and if the number of arbitration time periods contained in the arbitration frame is equal to the number of the data buses plus one, the last arbitration time period of the arbitration frame is used for checking whether the waiting communication nodes exist.

8. The data transmission method according to claim 7, wherein:

and if the communication nodes waiting in a queue exist in the last arbitration time period of the current arbitration frame, no self identifier is sent in the current arbitration frame.

9. The data transmission method according to claim 7, wherein:

if the current communication node continuously obtains arbitration success in an arbitration period and occupies a data bus to send data frames, when the times of continuously sending the data frames reach a specified number, a control module of the communication node controls a symbol sending module of the communication node to delay for a plurality of arbitration periods, and then the communication node enters a election queue of the data bus use right in the arbitration period; the number is customized by the system.