CN203847102U - CAN bus and 485 bus node circuit - Google Patents

Abstract

The utility model discloses a CAN bus and 485 bus node circuit which comprises a CPU, an isolator, a CAN bus and a 485 bus. The CPU is in data connection with the isolator, the CAN bus and the 485 bus are simultaneously connected with the isolator, an ADuM6402 chip is adopted for the isolator, a bus transceiver MAX3088 is adopted for the CAN bus, and a bus transceiver MAX3050 is adopted for the 485 bus. The CAN bus and 485 bus node circuit has the advantages of being simple, low in power consumption, small in size, good in stability, high in anti-jamming capability and adaptability and adjustable in CAN speed.

Description

CAN bus and 485 Bus Node Circuits

Technical field

The utility model belongs to logging technique field, relates to oil well logging real time data the spread of the rumours system, has specifically synchronously realized CAN bus and the design of 485 bus ground nodes, synchronously realized the electrical isolation of bus, and it is adjustable to have realized CAN bus data transfer rate.

Background technology

Along with the continuous exploration and development to petroleum resources for many years, more and more require people can identify low-resistivity, low-porosity, low-permeability, little oil-gas reservoir, just need to develop high-precision oil exploration equipment for produced on-site.Along with the raising of exploring equipment detection accuracy is had higher requirement to data communication.The development of field bus technique in recent years and be applied as this demand effective solution is provided.

1. at the scene in the variety of protocol of bus, CAN agreement has the advantages such as outstanding reliability, real-time and flexibility.CAN bus has following key property:

(l) CAN is with the work of many host modes, and on network, arbitrary node all can be at any time sends information to other nodes on network on one's own initiative, and regardless of principal and subordinate, communication mode is flexible, and without taking up an area the nodal informations such as location.Utilize this feature can form easily multi-level backup system.

(2) nodal information on CAN network is divided into different priority, can meet different requirement of real times.

(3) adopt non-destructive arbitration, when multiple nodes are during simultaneously to bus sending information, the node that priority is lower can exit transmission on one's own initiative, and the node of limit priority can continue to transmit data insusceptibly, thereby has greatly saved the bus collision arbitration time.Especially in the situation that offered load is very heavy, also there will not be network paralysis situation.

(4) adopt short frame structure, the transmission time is short, is disturbed probability low; Every frame information has CRC check and other error detection measure, and data error rate is extremely low.

(5) hardware interface of communication is simple, and order wire is few, and communication media can be twisted-pair feeder, coaxial cable or light, also can carry out communication by slip ring.

(6) node has the function of automatically closing output in the situation that mistake is serious, so that the operation of other node is unaffected in bus.

2. 485 buses have adopted two wires difference balance transmission technology, and have simple in structure, the advantage such as reliability is high, and antijamming capability is strong, its major function comprises:

(l) realized by 32 drivers of as many as and 32 real multi-point bus that receiver forms.

(2) common mode range of expansion in three-state driver and receiver, and can turn off.

(3) driver can stand bus conflict and bus failure.

3. in the time of actual design bus circuit, in order to strengthen the antijamming capability of system, need to increase buffer circuit.In existing bus isolation circuit, exist following deficiency:

(1) adopt photoelectric isolating circuit.Although photoelectric isolating circuit can strengthen the antijamming capability of system, also can increase the propagation delay time of the effective loop signal of bus, cause traffic rate or distance to reduce.And the shortcoming such as photoelectric isolating circuit volume is large, power consumption is higher, high-temperature behavior is weak, signal transmission precision is low.

(2) in multiple bus system, adopt many isolated from power.Isolated from power device need provide two groups of power supplys, otherwise isolation will lose due effect.In most multibus circuit, single bus adopts independently isolated from power, and this will make, and component increases, volume increases, and has increased complexity in circuits.

Traditional Bus Node Circuit adopts photoelectric isolating circuit more, and photoelectric isolating circuit has the deficiencies such as volume is large, power consumption is higher, high-temperature behavior is weak, signal transmission precision is low.If the multiple power supplies that adopt are isolated more in multibus node circuit, this certainly will increase the problem of complexity in circuits.

Summary of the invention

The utility model object is for a kind of Bus Node Circuit is provided, and adopt single circuit to realize the isolated from power of CAN bus and 485 buses, and CAN Bus Speed has adjustability.Overcome in prior art existing deficiency in conventional bus node circuit, there is the features such as low-power consumption, volume are little, good stability, antijamming capability is strong, adaptability is strong.

The utility model solves the technical scheme that its technical problem adopts: a kind of CAN bus and 485 Bus Node Circuits, comprise CPU, isolator and CAN bus and 485 buses, CPU sets up data with isolator and is connected, described isolator adopts ADuM6402 chip, CAN bus adopts bus transceiver MAX3088, 485 buses adopt bus transceiver MAX3050, the 12nd of ADuM6402 chip is connected with the 1st pin and the 4th pin of bus transceiver MAX3088 respectively with the 14th pin, the 7th pin of bus transceiver MAX3088 and the 6th pin are as 485 output end of main, the 13rd of ADuM6402 chip is connected with the 1st and the 4th pin of bus transceiver MAX3050 respectively with the 11st pin, the the 7th and the 6th pin of bus transceiver MAX3050 is as CAN output end of main.

Operating principle:

1.485 bus communications: micro controller CPU by send data be added to the transmitting terminal of 485 transceivers through isolating device ADuM6402, by 485, data are sent in 485 buses; By 485 bus transceivers, after isolating device ADuM6402 isolation, give CPU from the data-signal in 485 buses.

2.CAN bus communication: micro controller CPU by send data be added to the transmitting terminal of CAN transceiver through isolating device ADuM6402, by CAN, data are sent in CAN bus; By CAN bus transceiver, after isolating device ADuM6402 isolation, give CPU from the data-signal in CAN bus.

3. ADuM6402 is the digital isolator that ADI company releases, and this isolator adopts single power supply, provides four independently channel isolations, integrated isoPower isolated DC-DC converter.Converter is based on ADI company icoupler technology, while adopting 5V or 3.3V voltage, can provide the voltage stabilizing isolated power up to 500mW.Use wafer scale manufacturing process directly on chip, to manufacture icoupler transformer, this chip-scale icoupler passage is realized integrated between passage effectively than photoelectrical coupler, and more easily realizes other semiconductor functions.Adopt one group of power supply can realize the electrical isolation of CAN bus and 485 bus 4 road signals.Operating temperature reaches as high as 105 DEG C; (>25kV/ μ s) for high common mode transient immunity to interference.There is power supply and reference ground separately at the two ends that ADuM6204 isolates, and supply voltage is 5v, can realize like this low voltage power supply, thereby further reduces system power dissipation, and the power supply using in system is 5v.The centre of isolating chip ADuM6402 in system, is used for realizing the electrical isolation of circuit.ADuM6402 has eliminated the uncertain transfer rate of traditional photoisolator, nonlinear transfer function and temperature and the impact of life-span on device, without other drivings and discrete component, provide more stable conversion performance, and power consumption only has the 1/10-1/6 of photoisolator under identical signal transmission rate.In addition, ADuM has realized the electrical isolation between can bus node and between RS-485 bus node with one chip, meanwhile, replaces in the past multiple by 1 isolating chip, has greatly increased interchannel matching degree, makes system obtain better isolation performance.

Because the signal of micro controller output can not directly be connected with physical bus, must use bus transceiver, therefore the design is external two-way bus transceiver, a road is the bus transceiver MAX3050 based on can bus protocol, a road is the bus transceiver MAX3088 based on 485 bus protocols.Selected anti-interference control circuit, MAX3088 is the physical layer of 485 buses, and the differential sending and receiving function to 485 buses can be provided.MAX3050 is the physical layer of CAN bus, and the differential sending and receiving function to CAN bus can be provided, and regulates CAN traffic rate thereby MAX3050 external tapping can carry out transmission mode selection.Use MAX3050 and MAX3088 can increase communication distance, improve traffic rate, reduce system loss, improve the moment antijamming capability of system.

Because field condition is very complicated, between each node, there is very high common-mode voltage, although what CAN interface and 485 interfaces adopted is differential transfer mode, there is the ability of certain anti-common mode disturbances, but in the time that common-mode voltage exceedes the limit receiver voltage of CAN driver and 485 drivers, CAN driver and 485 drivers just cannot normally have been worked, when serious, even can burn chip and plant and instrument, therefore, in order to adapt to strong interference environment and high performance requirements, must carry out electrical isolation to the each communication node of bus.Native system has adopted the four-way digital isolator ADuM6402 of the novel single power supply of ADI company release.ADuM6402 has many places that is better than photoelectric isolating device performance, and ADuM6402 just can realize the object of the isolated from power of dual bus, not only reduced the complexity of system, also reduced the power consumption of system etc., ADuM6402 has greatly met the requirement of bus.

The utlity model has following characteristics:

1, adopt MAX3050 as CAN transceiver, adopt MAX3088 as 485 transceivers, the communication of realization and communication network, and design realizes CAN interface and 485 interface protections, anti-outer electrical interference.

2, the four-way numeral isolation characteristic that utilizes ADuM6402 to have, uses an isolator just synchronously independently to realize the electrical isolation of CAN interface, RS-485 interface and main circuit.

3, supply with one group of power supply of ADuM6402 isolator and can realize CAN Bus isolation and 485 Bus isolations.

4, CAN interface has message transmission rate regulatory function, and the speed of device reaches the transfer rate optimum Match with system, and it is reliable and stable, convenient to make to transmit.

5, this practical design novelly have that circuit is simple, the feature such as low-power consumption, volume are little, good stability, antijamming capability is strong, adaptability is strong, CAN speed is adjustable.

Brief description of the drawings

Fig. 1 is the utility model schematic block circuit diagram;

Fig. 2 is the circuit theory diagrams of the utility model isolator;

Fig. 3 is the circuit theory diagrams of the utility model isolator CAN bus;

Fig. 4 is the circuit theory diagrams of the utility model isolator 485 buses.

Detailed description of the invention

Referring to Fig. 1-Fig. 4, a kind of CAN bus and 485 Bus Node Circuits, comprise CPU, isolator and CAN bus and 485 buses, CPU sets up data with isolator and is connected, described isolator adopts ADuM6402 chip, CAN bus adopts bus transceiver MAX3088, and 485 buses adopt bus transceiver MAX3050.

1. 485 communications realize

The TX signal sending is exported through 14 pin after being input to isolating chip U1 (ADuM6402) 3 pin isolation, then be loaded into transmitting terminal 4 pin of 485 transceiver U2 (MAX3088), be driven into (R485+, RS485-) in 485 buses through U2 (MAX3088) variation sub-signal by 6 pin and 7 pin of U2; Differential signal R485+ and RS485-from 485 buses receive by 485 transceiver 7 pin and 6 pin, become reception signal and receive 12 pin of isolating chip U1 (ADuM6402) by 1 pin of U2, after U2 isolation, give CPU by 5 pin of U2 the signal receiving.2 pin of U2 are 485 reception control signals, the emissioning controling signal that 3 pin of U2 are 485, the two 485RD signal controlling of being exported by CPU that links together, 485RD signal default conditions are set to low level, make 485 in accepting state, in the time of transmitting data, it is high level that 485RD signal is set.C7, C8 are that capacitance is two electric capacity of 30p, the interference being used in filtering 485 buses; D1, D2 are two diode 1N714A of protection 485 buses; R4 is 120 ohm, is the build-out resistor of 485 buses, can carry out resistance adjustment coupling according to the distance of bus transfer distance.

2. CAN communication

Send after CAN-TX signal is input to isolating chip U1 (ADuM6402) 4 pin isolation and export through 13 pin, be connected to transmitting terminal 1 pin of CAN transceiver U3 (MAX3050), become differential signal through U3 (MAX3050) and be driven into (CANH, CANL) in CAN bus by 6 pin and 7 pin of U3; Differential signal CANH and CANL from CAN bus receive by CAN transceiver 7 pin and 6 pin, become reception signal and receive 11 pin of isolating chip U1 (ADuM6402) through 4 pin of U3, after U2 isolation, give CPU by 6 pin of U2 the signal receiving.C9, C10 are that capacitance is two electric capacity of 30p, the interference being used in filtering CAN bus; D3, D4 are two diode 1N714A of protection CAN bus; R3 is the potentiometer of 180K, regulates the speed of U3 (MAX3050), makes it to reach optimum Match with the speed of CAN bus; R5 is 120 ohm, is the build-out resistor of CAN bus, can carry out resistance adjustment coupling according to the distance of bus transfer distance.

The utility model is mainly for realizing 485 bus communication CAN bus communication and electrical isolation thereof, and port protection CAN interface iptimum speed is mated.Adopt advanced isolating device, CAN transceiver and 485 transceivers that reliable and stable, heat resistance is good.Two-way bus is reached and reliablely and stablely transmit data.

Claims (1)

1. a CAN bus and 485 Bus Node Circuits, comprise CPU, isolator and CAN bus and 485 buses, CPU sets up data with isolator and is connected, it is characterized in that: described isolator adopts ADuM6402 chip, CAN bus adopts bus transceiver MAX3088, 485 buses adopt bus transceiver MAX3050, the 12nd of ADuM6402 chip is connected with the 1st pin and the 4th pin of bus transceiver MAX3088 respectively with the 14th pin, the 7th pin of bus transceiver MAX3088 and the 6th pin are as 485 output end of main, the 13rd of ADuM6402 chip is connected with the 1st and the 4th pin of bus transceiver MAX3050 respectively with the 11st pin, the the 7th and the 6th pin of bus transceiver MAX3050 is as CAN output end of main.