CN102780705B - Ethernet-(controller area network) CAN protocol converter - Google Patents
Ethernet-(controller area network) CAN protocol converter Download PDFInfo
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Abstract
The invention discloses an Ethernet-(controller area network) CAN protocol converter which is composed of a microcontroller (1), a peripheral circuit (2), a CAN module (3) and an Ethernet module (4). The microcontroller (1) is connected with the peripheral circuit (2), the CAN module (3) and the Ethernet module (4) respectively. The Ethernet-CAN protocol converter can achieve the conversion from CAN protocol data to Ethernet frames and from Ethernet frames to CAN protocol data. The Ethernet-CAN protocol converter solves the mutual conversion problem of two formats of data of CAN protocol data and Ethernet frames. Directed at problems that short frames waste bandwidth and is prone to cause network congestion and the like, the Ethernet-CAN protocol converter achieves Nagle algorithm in a transmission control protocol (TCP), reduces the number of short frames greatly, and saves the bandwidth.
Description
Technical field
The present invention relates to industrial control field, particularly a kind of protocol converter realized based on the Industrial Ethernet of TCP/IP technology and the intercommunication of CAN.
Background technology
Ethernet technology enters industrial control field at the beginning of the nineties in last century, high with its opening, compatible good, expand the features such as flexible, achieve significant progress.Field bus technique is real-time, reliability is high, but fails to realize trans-regional network connection.Therefore the pattern that Ethernet-fieldbus combines has become the emphasis of Industry Control development.
CAN is the Typical Representative of current fieldbus.
TCP/IP technology has good practicality and exploration, and the Ethernet based on TCP/IP technology has been widely used in industrial communication.
There is short frame data report (1-4 byte) in industry spot in a large number, make bandwidth availability ratio extremely low, the possibility of congested generation also increases.Nagle algorithm is as the standard of TCP congestion control, short frame flooding problem can well be solved, but when slave computer nagle algorithm and host computer delayed acknowledgement strategy (Delayed Ack) carry out mutual, be easy to produce temporary " deadlock " (" deadlock ") phenomenon, cause data can not real-time Transmission.For temporary " deadlock " phenomenon, generally there are now two kinds of solutions: one closes nagle algorithm, but to sacrifice bandwidth for cost; Another kind be adopt improve nagle algorithm, comparatively speaking more complicated, enforcement is more difficult and versatility is not strong.
Summary of the invention
In order to solve above-mentioned technical problem of the prior art, the invention provides that a kind of volume is little, structure simple rigid, with low cost, reliability is high, can meet the Ethernet-CAN protocol converter of Industry Control real-time needs.
Described Ethernet-CAN protocol converter, be made up of microcontroller, peripheral circuit, CAN module and Ethernet module, described microcontroller is connected with Ethernet module with peripheral circuit, CAN module respectively, described CAN module is made up of CAN transceiver and CAN interface, described Ethernet module is made up of the RJ45 socket of ethernet PHY transceiver and integrated network isolating transformer, described Ethernet-CAN protocol converter can realize the conversion from CAN protocol data to Ethernet frame, and from Ethernet frame to the conversion of CAN protocol data.
Further, described Ethernet-CAN protocol converter embedded in ICP/IP protocol stack, realizes TCP, IP, ARP, ICMP agreement.
Further, use custom protocol in its application layer, the data format of described custom protocol comprises: representative data flows to Flag field, represents the CAN_ID field of CAN node ID and the CAN_DATA field of representative data.
Further, nagle algorithm is used in Transmission Control Protocol, workflow is: TCP transmitting terminal receives the data that application layer produces, if now meet two conditions: the confirmation or the tcp data length that receive last packet have reached maximum message segment segment length (MSS), send tcp data immediately; Otherwise the data chunks received by TCP, until trigger above-mentioned two conditions.
Further, different with data type to requirement of real-time according to data-signal, data-signal is divided into high, medium and low three priority.
Further, processed mechanism is taked for application layer data, workflow is: take the processing mode of filling buffering area to high-priority data, if namely TCP receives the high-priority data that application layer produces, immediately by this data stuffing to maximum message segment segment length, trigger the transmission data qualification of nagle algorithm, send data and need not the arrival of wait acknowledge immediately; Centering priority data takes the processing mode improving sample frequency, namely improves such data sampling frequency, makes it in 200ms, produce the message that equals MSS, thus breaks " deadlock " mechanism; For lower-priority data signal, the signal of 200ms propagation delay time can be tolerated, do not process.
Further, describedly from CAN protocol data to the transfer process of Ethernet frame be:
1. start CAN module and receive data;
If 2. receive data, be saved in application layer buffering area; If the data of not receiving, return step 1.;
3. priority mechanism process is taked to the data in application layer buffering area;
If 4. now meet nagle algorithm to send data qualification, TCP/IP package carried out to application layer buffer data and sends immediately, returning step 1.; If now do not meet nagle algorithm to send data qualification, return step 1..
Further, describedly from CAN protocol data to the transfer process of Ethernet frame be:
1. start Ethernet module and receive data;
If 2. there are data Ethernet module reception buffer zone, judge network layer protocol type; If Ethernet module reception buffer zone does not have data, return step 1.;
If 3. step 2. in network layer protocol type be ARP agreement, 1. process ARP message, return step; If step 2. middle network layer protocol type is IP agreement, process IP message;
4. determining step 3. in the upper-layer protocol type that carries of IP message, if be ICMP agreement, process icmp packet, return step 1.; If be Transmission Control Protocol, 1. process TCP message, return step;
If 5. step 4. in TCP message carry CAN data, send CAN data, return step 1.; Otherwise directly return step 1..
The effect that the present invention brings is: realize the mutual conversion between ICP/IP protocol and CAN protocol, can realize the intercommunication of Ethernet and CAN.For a large amount of short frame data report, in Transmission Control Protocol, realize nagle algorithm, significantly reduce short frame data bag quantity, save the network bandwidth, reduce the possibility of network congestion generation.The signal high to requirement of real-time, under the prerequisite not revising nagle algorithm, adopts the measure of filling buffering area or improving sample frequency, eliminates temporary " deadlock " phenomenon, ensure the real-time of transfer of data.
Accompanying drawing explanation
Fig. 1 is Ethernet-CAN protocol converter execution mode schematic diagram
Fig. 2 is Ethernet-CAN protocol converter structured flowchart
Fig. 3 is Ethernet-CAN protocol converter data handling procedure figure
Fig. 4 is Ethernet-CAN protocol converter agreement flow chart
Fig. 5 is application layer custom protocol data format
Fig. 6 is nagle algorithm workflow diagram
Fig. 7 is nagle algorithm and delayed acknowledgement strategy interactive mode figure
Fig. 8 is sample frequency is 1 byte/ms RTT distribution map
Fig. 9 is sample frequency is 10 bytes/ms RTT distribution map
Figure 10 is priority working mechanism flow chart
Figure 11 is Ethernet-CAN protocol converter workflow diagram
Embodiment
Below in conjunction with accompanying drawing, the invention will be further described.
As shown in Figure 1, Fig. 1 is Ethernet-CAN protocol converter execution mode schematic diagram.Ethernet-CAN protocol converter of the present invention, as the bridge between CAN and Ethernet, realizes the intercommunication mutually between CAN and Ethernet.
Fig. 2 is Ethernet-CAN protocol converter structured flowchart.Described Ethernet-CAN protocol converter is made up of microcontroller 1, peripheral circuit 2, CAN module 3, Ethernet module 4 in hardware designs.Described CAN module 3 is made up of CAN transceiver and CAN interface.Described Ethernet module 4 is made up of the RJ45 socket of ethernet PHY transceiver and integrated network isolating transformer.
Described microcontroller 1 is the core of described Ethernet-CAN protocol converter, is connected respectively with peripheral circuit 2, CAN module 3 with Ethernet module 4, realizes the mutual conversion between CAN protocol data and these two kinds of formatted datas of ethernet frame.The ARM7 family chip LPC2368 that the present invention selects PHILIPS Co. to produce is as microcontroller 1.
Described peripheral circuit 2 is the minimum system circuit of described microcontroller 1, comprises clock circuit, reset circuit, power circuit and jtag interface circuit.It should be noted that, the external clock crystal oscillator frequency that the present invention adopts is 11.0592MHz, and the power circuit of employing is 5V-3.3V DC power supply circuit.
Described CAN module 3 is made up of CAN transceiver and CAN interface two parts.CAN transceiver is transmitted and receive data respectively by bus CANH and CANL, and CAN interface provides input/output interface for bus CANH and CANL.Adopt TJA1040 chip as CAN transceiver in the present invention.
Described Ethernet module 4 is made up of the RJ45 socket of ethernet PHY transceiver and integrated network isolating transformer.Ethernet PHY transceiver has the functions such as data-signal transmitting-receiving, Manchester Code/decode and collision detection.The present invention adopts DM9161AEP chip as ethernet PHY transceiver, selects J00-0061NL as RJ45 socket.This Outlet integrated network isolating transformer is integrated, and can play the effect of restraining common mode disturbances, isolating circuit and impedance matching.
Fig. 3 is Ethernet-CAN protocol converter data handling procedure figure.Direction 1->2 is CAN data-> Ethernet data transfer process: the data-signal received is sent to the physical layer of CAN by CAN interface, after CAN physical layer and data link layer deals, obtain application layer data.Application layer data is converted to Ethernet data signal successively and is sent by RJ45 socket after the process of the transport layer of Ethernet, network layer, data link layer and physical layer.Direction 2->1 is Ethernet data->CAN data conversion process: the data-signal received is sent to the physical layer of Ethernet by RJ45 socket, successively after the process of the physical layer of Ethernet, data link layer, network layer and transport layer, obtain application layer data.Application layer data is converted to CAN data-signal through the data link layer of CAN and the process of physical layer successively and is sent by CAN interface.
Fig. 4 is Ethernet-CAN protocol converter agreement flow chart.Application layer protocol is custom protocol, and Fig. 5 is application layer custom protocol data format.In described Fig. 5, Flag representative data flows to, and length is 1 byte, direction 2->1 in direction 1->2,0xFE representative graph 3 in 0xFF representative graph 3.CAN_ID length is 2 bytes, represents CAN node ID.CAN_DATA length is not limit, and is generally several to dozens of bytes.Here only provide a kind of protocol definition mode, user can self-defined application layer protocol according to actual needs, repeats no more here.The present invention realizes Transmission Control Protocol in transport layer, realizes IP, ICMP, ARP agreement in network layer.As for physical layer and the data link layer functions of CAN and Ethernet, realize by corresponding hardware and driver.
Fig. 6 is nagle algorithm workflow diagram.Because CAN adopts short frame structure, short frame data bag existence a large amount of in network can cause bandwidth availability ratio to reduce and the possibility of congested generation increases, and therefore the present invention realizes nagle algorithm in Transmission Control Protocol.Specific works flow process is as shown in Figure 6: TCP transmitting terminal receives the data that application layer produces, if now receive last packet confirmation or now tcp data length reached maximum message segment segment length (MSS), send tcp data immediately.Otherwise the data chunks received by TCP, until trigger above-mentioned two conditions.The essence of nagle algorithm is chunk technology.The present invention embeds nagle algorithm in Transmission Control Protocol, can reach the object significantly reducing short frame data bag quantity in network, save the network bandwidth.
Fig. 7 is nagle algorithm and delayed acknowledgement strategy interactive mode figure.In mode one, transmitting terminal sends data1 to receiving terminal, carries out chunk to the data of the follow-up generation of application layer simultaneously; After receiving data, receiving terminal sets the timer of a 200-500ms (representative value is 200ms), and after time-out, receiving terminal produces immediately and confirms bag, and transmitting terminal sends data2 after the confirmation receiving data1.In mode two, after transmitting terminal sends data1, before receiving terminal timer expiry, transmitting terminal generates one and reaches the message data2 of MSS and send immediately, receiving terminal sends immediately and confirms bag after receiving two unacknowledged messages continuously, deletes timer simultaneously.Mode one all can produce the time delay of at least 200ms in data exchange process each time, is also referred to as temporary " deadlock " (" deadlock ").If system real time is less demanding, under identical application layer data produces speed, the chunk effect of mode one is optimal, because its delay time is maximum.In the system that requirement of real-time is higher, mode two is more better than the effect of mode one.The present invention starts with from data-signal type, different for its priority, selects different interactive modes, guarantees the requirement of real-time of data-signal.
Table 1 is data priority classification and respective handling mode schematic diagram.The present invention arranges high, medium and low three kinds of priority type.
| Priority | 0.2s time delay can be tolerated | Data-signal type | Processing mode |
| High | Can not | Random signal | Fill buffering area |
| In | Can not | Cyclical signal | Improve sample frequency |
| Low | Energy | - | - |
Table 1
High-priority data need possess following two conditions: 1. random signal; 2. can't stand the propagation delay time of 200ms.The present invention takes the processing mode of filling buffering area to high-priority data.If namely TCP receives the high-priority data that application layer produces, immediately by this data stuffing to maximum message segment segment length, trigger the transmission data qualification of nagle algorithm, immediately transmission data and need not the arrival of wait acknowledge.
Medium priority data need possess following two conditions: 1. cyclical signal; 2. can't stand the propagation delay time of 200ms.Centering priority data of the present invention takes the processing mode improving sample frequency.Namely improve such data sampling frequency, make it in 200ms, produce the message that equals MSS, thus break " deadlock " mechanism.Fig. 8 and Fig. 9 is respectively the RTT contrast that sample frequency is 1 byte/ms and 10 bytes/ms, and condition is MSS=1460 byte.
For lower-priority data signal, can tolerate the signal of 200ms propagation delay time, the present invention does not process, and due to now time of delay the longest, chunk effect is best.Figure 10 is priority working mechanism flow chart.
Figure 11 is described Ethernet-CAN protocol converter workflow diagram.After hardware initialization completes, respectively according to the direction of 1->2 shown in Fig. 3 and 2->1 direction deal with data.
1->2 bearing data processing procedure:
1. start CAN module and receive data;
If 2. receive data, be saved in application layer buffering area; If the data of not receiving, return step 1.;
3. priority mechanism process is taked to the data in application layer buffering area;
If 4. now meet nagle algorithm to send data qualification, TCP/IP package carried out to application layer buffer data and sends immediately, returning step 1.; If now do not meet nagle algorithm to send data qualification, return step 1..
2->1 bearing data processing procedure:
1. start Ethernet module and receive data;
If 2. there are data Ethernet reception buffer zone, judge network layer protocol type; If Ethernet reception buffer zone does not have data, return step 1.;
If 3. step 2. in network layer protocol type be ARP agreement, 1. process ARP message, return step; If step 2. middle network layer protocol type is IP agreement, process IP message;
4. determining step 3. in the upper-layer protocol type that carries of IP message, if be ICMP agreement, process icmp packet, return step 1.; If be Transmission Control Protocol, 1. process TCP message, return step;
If 5. step 4. in TCP message carry CAN data, send CAN data, return step 1.; Otherwise directly return step 1..
Shown in the above and figure is only the preferred embodiment of the present invention.It should be pointed out that for the person of ordinary skill of the art, under the prerequisite not departing from principle of the present invention, can also make some modification and improvement, these also should be considered as belonging to protection scope of the present invention.
Claims (6)
1. an Ethernet-CAN protocol converter, by microcontroller (1), peripheral circuit (2), CAN module (3) and Ethernet module (4) composition, described microcontroller (1) respectively with peripheral circuit (2), CAN module (3) is connected with Ethernet module (4), it is characterized in that: described CAN module (3) is made up of CAN transceiver and CAN interface, described Ethernet module (4) is made up of the RJ45 socket of ethernet PHY transceiver and integrated network isolating transformer, described Ethernet-CAN protocol converter can realize the conversion from CAN protocol data to Ethernet frame, with from Ethernet frame to the conversion of CAN protocol data,
Describedly from Ethernet frame to the transfer process of CAN protocol data be:
1. start CAN module (3) and receive data;
If 2. receive data, be saved in application layer buffering area; If the data of not receiving, return step 1.;
3. priority mechanism process is taked to the data in application layer buffering area;
If 4. now meet nagle algorithm to send data qualification, TCP/IP package carried out to application layer buffer data and sends immediately, returning step 1.; If now do not meet nagle algorithm to send data qualification, return step 1.;
Describedly from CAN protocol data to the transfer process of Ethernet frame be:
One. start Ethernet module (4) and receive data;
Two. if there are data Ethernet module (4) reception buffer zone, judges network layer protocol type; If Ethernet module (4) reception buffer zone does not have data, return step one;
Three. if in step 2, network layer protocol type is ARP agreement, and process ARP message, returns step one; If in step 2, network layer protocol type is IP agreement, process IP message;
Four. the upper-layer protocol type that in determining step three, IP message carries, if be ICMP agreement, process icmp packet, returns step one; If be Transmission Control Protocol, process TCP message, returns step one;
Five. if in step 4, TCP message carries CAN data, sends CAN data, returns step one; Otherwise directly return step one.
2. Ethernet-CAN protocol converter according to claim 1, is characterized in that: described Ethernet-CAN protocol converter embedded in ICP/IP protocol stack, realizes TCP, IP, ARP, ICMP agreement.
3. Ethernet-CAN protocol converter according to claim 2, it is characterized in that: use custom protocol in its application layer, the data format of described custom protocol comprises: representative data flows to Flag field, represents the CAN_ID field of CAN node ID and the CAN_DATA field of representative data.
4. Ethernet-CAN protocol converter according to claim 2, it is characterized in that: in Transmission Control Protocol, use nagle algorithm, workflow is: TCP transmitting terminal receives the data that application layer produces, if now meet two conditions: the confirmation or the tcp data length that receive last packet have reached maximum message segment segment length (MSS), send tcp data immediately; Otherwise the data chunks received by TCP, until trigger above-mentioned two conditions.
5. Ethernet-CAN protocol converter according to claim 4, is characterized in that: different with data type to requirement of real-time according to data-signal, data-signal is divided into high, medium and low three priority.
6. Ethernet-CAN protocol converter according to claim 5, it is characterized in that: processed mechanism is taked for application layer data, workflow is: take the processing mode of filling buffering area to high-priority data, if namely TCP receives the high-priority data that application layer produces, immediately by this data stuffing to maximum message segment segment length, trigger the transmission data qualification of nagle algorithm, send data and need not the arrival of wait acknowledge immediately; Centering priority data takes the processing mode improving sample frequency, namely improves such data sampling frequency, makes it in 200ms, produce the message that equals MSS, thus breaks " deadlock " mechanism; For lower-priority data signal, the signal of 200ms propagation delay time can be tolerated, do not process.
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| CN105099945A (en) * | 2014-04-24 | 2015-11-25 | 比亚迪股份有限公司 | CAN network system and packet transmission control method |
| CN105827647A (en) * | 2016-05-18 | 2016-08-03 | 浙江京禾电子科技有限公司 | Protocol converter |
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| US20180092115A1 (en) * | 2016-09-29 | 2018-03-29 | Qualcomm Incorporated | Reliable wi-fi packet delivery using delayed/scheduled block acknowledgment mechanism |
| CN107171916B (en) * | 2017-04-07 | 2020-08-18 | 浙江工业大学 | Special 4G wireless intelligent network bridge for remote monitoring of industrial metering pump |
| CN107517225B (en) * | 2017-09-30 | 2020-06-05 | 北京东土军悦科技有限公司 | Protocol conversion method, gateway equipment and storage medium |
| CN108551423A (en) * | 2018-04-11 | 2018-09-18 | 浙江工业大学 | The special multichannel intelligent gateway of industry measurement pump group cluster remote monitoring |
| CN111385177A (en) * | 2018-12-27 | 2020-07-07 | 比亚迪股份有限公司 | Vehicle and communication system and method thereof |
| CN109818844B (en) * | 2019-04-11 | 2020-12-29 | 西南交通大学 | Communication gateway and method for converting automobile Ethernet bus into CAN bus |
| CN110336725B (en) * | 2019-07-11 | 2020-11-10 | 珠海格力电器股份有限公司 | Method and device for accurately positioning nodes in Controller Area Network (CAN) network |
| TWI731592B (en) * | 2020-02-19 | 2021-06-21 | 台達電子工業股份有限公司 | Cross-protocols control apparatus with apparatus-restoring function and method of restoring apparatus for cross-protocols thereof |
| CN114667716A (en) * | 2020-10-19 | 2022-06-24 | 日产自动车株式会社 | Relay device, communication network system, and communication control method |
| EP4221104A1 (en) | 2022-01-28 | 2023-08-02 | Nxp B.V. | Network interface apparatus |
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