How to Accelerate the Development of FF Fieldbus Automation Intelligent Instrument

At present, the ongoing automation technology innovation led by fieldbus technology in the world is the fourth generation intelligent digital product of instrumentation. The application of this product must be universal, networked and open. Only on the basis that everyone uses a unified fieldbus standard and has interoperability, can the expanded network application be truly realized. In this regard, in the face of HART instruments and international foundation fieldbus technology has been or is mature today, how to accelerate the development of domestic intelligent instruments is a thing that must be considered in the industry.

Ⅰ What Kind of Special Chip Is Used

At present, the largest number of international and domestic intelligent instruments are HART, accounting for 40%, followed by FF H1 and PROFIBUS PA accounting for 10%, and the remaining analog instruments account for 50%. The transformation object is for this part of the instrument, and the developed products should take into account both HART and two kinds of buses.

The content of the development is mainly related to the communication chip of the fieldbus and the intelligent template of the instrument, which can be made separately or combined. The tools to be used in the development process are the developed suite and source code, and after the initial completion, go to the relevant international units for testing and certification.

The development of intelligent bus instruments requires higher technologies such as digitization, computer and network, and the general domestic enterprises do not want the high investment in the early stage. In addition, the development process needs to first obtain the necessary qualifications and corresponding standards, these conditions hinder the pace of development of domestic manufacturers.

During the Ninth five-year Plan and the Tenth five-year Plan period, the Ministry of Science and Technology and the National Development and Reform Commission set up projects to subsidize development work and achieved success in the Shenyang Institute of Automation of the Chinese Academy of Sciences. The follow-up development of domestic enterprises should take the form of cooperation to reduce development time and develop more products.

Ⅱ Varieties of Chips Developed

According to the needs of the market, at present, some varieties are the special chip FBC0409 for FF H1 and PROFIBUS PA bus products and the special chip HT1200M for HART bus products. Their respective characteristics are:

1. FBC0409 Special Chip

2. Adopt low-speed bus 31.25Kbit/S data transfer rate, Manchester coding, with automatic line polarity identification and correction, 44-pin QFP package; adapt to most microprocessor interfaces, embedded 4K BYTE RAM units, can store bus messages; provide DMA controller and bus arbiter to achieve efficient bus data sending and receiving; support sending, receiving, destination address identification and internal bus arbitration mechanism to improve the efficiency of message processing Provide 1ms, 1/32ms, OCTET time three kinds of timer, can meet the protocol timing requirements; FBC0409 typical application circuit.

3. HT1200M Special Chip

HT1200M is a low-power modulation and demodulation chip for HART product development. It only needs a small number of external components to complete the design of HART signal modulation and demodulation circuit. It is the most ideal communication chip in performance, cost, quality and other aspects. HT1200M is fully compatible with the performance, function and pin of HT20C15 and SYM20C15 chips widely used in the market, and can be directly replaced.

The chip uses a monolithic, half-duplex 1200b/s rate frequency shift keying modem, integrated receiving bandpass filter circuit and transmit signal waveform shaping circuit, external 460.8kHz crystal or ceramic filter and internal clock oscillator or external clock input.

Ⅲ How to Develop Fieldbus Protocol Software

Using the traditional development mode to develop the bus instrument communication protocol has the advantages of great technical difficulty, long debugging time and large investment. If the new mainstream technology integration mode is adopted, the development speed can be accelerated, the testing cost can be reduced, and the instrument can be put into the market quickly.

1. Characteristics of FF communication protocol stack.

At present, Shenyang Microcyber Corporation has developed and completed the software development of FF H1 and HSE protocol stack respectively, and realized the conversion function between HSE and H1 protocol. Through the FF conformance test and interoperability test, the protocol stack supports standard FMS,SM service, Link Master function, transform block, standard function block and advanced function block, and supports function block instantiation. The development process provides functional block source file templates.

The integrated development platform also supports PROFIBUS PA protocol and can be used to develop Profibus PA products.

2. The software source code of the optional protocol stack

In order to speed up the development of stack protocol software source code, the shortest way is to use the existing source code for migration. At present, the source code of the successfully developed FF H1 and Profibus PA is based on the FBC0409 special chip. This source code is written in standard C code and uses the Nncleus operating system.

3. Choose and purchase protocol stack development kit

For users, the necessary condition is that technicians need to have a certain digital instrument development ability, can read and use protocols or auxiliary development text. The conditions that can be provided are: hardware schematic diagram, PCB diagram, device capability file (CFF) description template (FF H1), device description template source code (DDL language, FF H1), GSD file template (text file, Profibus PA), function block source code (C language) and protocol library (FF H1 or Profibus PA) and operating system interface hardware.

When developing round cards, the most important thing is to master the development kit tools, including Fieldbus ToolKit For FF/PA. If these tools are members of the foundation, they can be obtained from the foundation, and if they are not members, they must be developed jointly with the help of the technical reserves of the partner.

Ⅳ The Composition of Fieldbus Communication Module

Choosing fieldbus communication module for OEM customization development is one of the fast and effective product development methods. What needs to be considered here is the use of serial port: data exchange through asynchronous serial port UART, custom communication protocol, or Imax O interface: the physical signals of resistance and voltage are collected directly through Imax O interface, in order to determine how to design a balance between power consumption, function, performance and power consumption of the instrument card.

1. Fieldbus Communication Module

The communication module is suitable for temperature, pressure, flow rate, liquid level and actuator in automatic instruments.

All communication modules in the above instruments must meet the following conditions, namely, protocol conformance testing, FF/PA international testing, EMC certification and intrinsically safe certification, etc., so that they can be formally installed on the market in the instrument.

2. Technical Index of FF/PA Round Card

CPU:AT91M0800

FLASH:512K

RAM:1M

Bus power supply: 9~32VDC

Bus current: ≤ 15mA

Operating temperature:-30 ℃ ~ + 70 ℃

Instrument accuracy: 0.1%

Support FF H1 standard function blocks (AI, AO, DI, DO, PID, IS, etc.), or support Profibus PA standard function blocks (AI, AO, DI, DO).

3. The Technical Specification of HART Fieldbus Round Card.

Pass the physical layer conformance test

4~20mA output overlay HART protocol digital communication (two-wire system)

It can be managed remotely by handset or PC configuration debugging software.

Passed the IECEx system explosion-proof certification

Passed the electromagnetic compatibility test certification

Support CPU fault alarm, write protection jumper

Interface card communication: serial port and Ithumb O mode, up to 4 Icano

Connection to the sensor: Optocoupler isolation

Ⅴ Development of Fieldbus Control System

On the basis of completing the development of the general linear intelligent instrument, the cooperative development of the bus control system can be carried out, which requires that the user should have a certain system integration ability and is using a certain control system. on this basis, it is possible to master the more difficult fieldbus control system by reforming, upgrading and transplanting software and hardware.

At present, the projects of Microcyber Corporation are fieldbus control system (NCS4000), equipped with dedicated integrated controller (NCS-MPLC) and FF gateway equipment (NCS-LD105). For automatic instrument enterprises, there may be many factors to be considered in the follow-up system development, and a long-term development plan should be made according to their own and market conditions.

At present, Shenyang Institute of Automation, Chinese Academy of Sciences, Microcyber Corporation and a number of domestic and foreign enterprises have jointly developed a number of products, including pressure transmitter, temperature transmitter, electromagnetic flowmeter, electric actuator, actuator and so on. Hope to adopt the way of OEM, the two sides in line with their respective advantages, cooperation, will be able to develop domestic intelligent bus products.

Shenyang Institute of Automation, Chinese Academy of Sciences and Microcyber Corporation are members of the International fieldbus Foundation. We hope that domestic qualified units will join the fieldbus Foundation. At the same time, we are also welcome to make use of our experience and existing products to carry out OEM development and jointly improve intelligent instruments.