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The IP-based load sensor design W3100A

Published on Jan 20 2011 // Sensor application circuits

 The IP- load sensor design based on W3100A 1

Abstract: Embedded IP-based W31OOA Ha load sensor structure of several of its network interface implementations; focused on the based on TCP / IP protocol stack chip W3100A’s network interface and Web capabilities to achieve; given load sensors embedded IP an application example.
  Keywords: IP sensor network interfaces W31OOA Weight Sensor
  Industrial production, the traditional control system have been moved from centralized to decentralized direction. Distribution in the field of smart sensors and actuators is growing, more and more among them showed the urgent need for communication. With the rapid development of Intelnet, TCP / IP protocol is becoming a world-wide network communication protocol standards. If you let in on-site sensors to achieve TCP / IP protocol, which is embedded in the network connection to the site sensor, the traditional sensors really become a separate network node, data acquisition, information transmission can be directly on the Intranet / Internet on the Web the way, both the unified standard, but also reached the remote control and operation purposes. Embedded IP-based load sensor W3IOOA to achieve this purpose it is designed.
  1 IP load sensor structure
  IP load sensors embedded in smart sensors developed on the basis of a new type of sensor has the Internet capabilities. Its essence is in the tradition of the sensor based on the TCP / IP network communication protocol interface, the sensor nodes as the network directly with the computer network communication. Its composition are: Sensitive, Smart processing unit and TCP / IP communication protocol interface.
  Figure l load sensor for embedded IP block diagram. The sensor works as follows: the traditional sensors measured load signal is converted to electrical signals, first through the A / D converter is converted to digital signals, then through the microprocessor’s data processing (filtering, calibration) will send the results to the network ; and network data exchange by the TCP / IP-protocol network interface module. IP load sensors embedded internal memory storage of the physical characteristics of the sensor, such as offset, sensitivity, calibration parameters; microprocessor for data processing and output calibration; TCP / IP protocol sensor network. Compared with traditional sensors, embedded IP sensor based W3100A reliable, cheap, good scalability advantages, but also directly to the raw data in the internal processing, handling, and through the Intranet / Internet data exchange with the outside world, so it with miniaturization, networking and intelligent features. Since the sensor can be used with Intranet / Internet interconnection, which realized the sharing of resources.

2 TCP / lP protocol stack implementations of several
  IP sensor network to achieve the key interface design, and network interface is the key to TCP / IP Communication Protocol. Currently, methods to achieve the following two:
  based software to TCP / IP protocol stack. By TCP / IP protocol stack ported to the system, and then call the relevant API functions for network communication. Or not to use portable way, with reference to the standard TCP / IP protocol to streamline the corresponding protocol layer, the preparation of related API functions to complete a simple TCP / IP communications. But this method requires the operating system, high-performance MCU and mass storage support.
directly using TCP / IP protocol stack chips. The main advantage of such a program, application system design do not consider any network protocol, only the network chip that interprets and executes instructions and data transmission over can be achieved with the Internet network connection, data transmission network and no operator system support. Based on Embedded IP W3IOOA load sensor chip using this method is implemented.
  3 sensor system hardware design
  About 3.1 W3100A chip
  W3100A is produced by a South Korean Wiznet TCP/1P chip stack, which contains the protocol layer are TCP (Transmission Control Protocol), IP (Internet Protocol), UDP (User Datagram Protocol), ICMP (network control message by holding Protocol) and the protocol DLC (data link control), and the MAC protocol. The chip provides two interfaces to the upper application layer – MCU interface and I2C interface, an MII (Media Independent Interface) interface to the underlying physical layer. Chip supports full-duplex 4 M ~ 5 Mb / s data communications; internal data with the dual port RAM buffer, 64-pin LQFP package, the internal structure shown in Figure 2.

 The IP- load sensor design based on W3100A 2

512 B-chip control registers provide storage space and 16 KB of data storage buffer. Which transmit data buffer 8 KB for data transmission with Mcu, MCU can only write but not read; 8 KB Receive data buffer used to receive data for MCU, MCU can only be read but not write. Register for the MCU chip provides access to specific registers are classified as follows; control register (command, status and interrupt); system register (gateway address, subnet mask, IP address, etc.); for data collection, issued by the pointer register; channel operation of channel registers. See all register functions and address of the literature.
  3.2 Hardware Interface and Data Transfer
  W3100A provides two ways to achieve parallel and serial communication with the MCU. Figure 3 shows the 12C-based serial port connection. MCU in which the sensor processor, Ethernet physical layer device used RTIL8201 chip. W3100A provides MII interface RTL820l connected, which lead RX_CLK, RXDV, RXD [3; O], and COL for data reception, and TX_CLK, TXE, TXD [3: O] for data transmission. Provide simulated MCU I2C interface W3lOOA communication. I2C is a serial communication bus mode, the data line SDA and SCL clock line with the completion of communication.

TCP connection active connection points (TCP client mode) and the passive connection (TCP server mode). This paper uses a passive TCP connection, the specific procedure shown in Figure 4. First of all, to complete the chip TCP / IP initialization, the initialization key is necessary to register for the appropriate settings. These registers include the GAR, SMR, SHAR, and SIPR and so on.

The register is set by executing the control register after the 0 Sys_init CO_CR activated chip. Second, set the appropriate channels, such as 0-channel, select the protocol register C0_SOPR as 0X01, select the TCP protocol. Channel O control register CO_CR implementation of Socket_Init, while C0_Tw_PR, C0_TR_PR and CO_TA_PR set into the same value. And then run the Connect and Listen C0_CR command bits, TCP connection establishment.
  TCP data transmission and reception should be carried out after the connection is established, by setting the RMSR and TMSR to specify the data buffer space. TCP data transmission process is through the use of C0_TW_PR, CO_TA_PR to carry out, their initial value the same. Then MCU to transmit data according to how much value added C0_TW_PR. Finally, C0_TW_PR, C0_TA_PR the difference between a free data buffer space for the implementation of transfer orders, while increasing the value of C0_TA_PR, data transfer and their values after the same.
  4 Sensor system software design
  IP load sensor workflow is: first load signal acquisition, followed by the signal A / D conversion will result is stored in EEPROM, and can be embedded into the signal and processing the results of the pre-stored in the EEPROM page customized for a good client access through the Internet, while on the local LCD display data load signal. W31130A works similarly to Windows, Socket API, so the program is in Cygnal’s integrated development environment, the apparatus as a server, based on the Socket API using C language. On the C8051F021, since to do is W3100A TCP protocol, the procedures are simple and many. Communications main program flow shown in Figure 5.

Network configuration files are stored in advance EEPR () M, for the local IP address of the instrument is set to a static IP address, a static IP address if not you can use Dynamic Host Configuration Protocol (DHCP) to dynamically obtain an IP address.
  5 Application
  Sodium dichromate is an important inorganic chemical raw materials. In the production of sodium dichromate, ingredient is a very important process. The scene of appalling conditions as ingredients, infected more than dust, noise, seriously affecting the health of workers […. Traditional computer batching system, given its limited capacity remote sensor, remote monitoring system of ingredients is often inadequate, so that the development of sensor web capabilities of IP is essential. IP-based sensor system block diagram of sodium dichromate ingredients shown in Figure 6.

Web-work system, C / S model, the sensor by the Web browsers and Web servers constitute, an agreement between the two communicate using HTTP, so the upper layer protocol in the sensor should be used HTTP protocol. At the same time to achieve an embedded Web browser and interact with the sensor, in addition to solving the TCP / IP communication protocol interfaces, the sensor should provide an EEPROM memory corresponding web document. Interact, HTTP through the Uniform Resource Locator URL (Uniforrm Resource Locator) to determine the sensor should be on what resources the browser. To save space, through a flexible Hllsh algorithm. EEPROM for each file has a different value corresponding Hush, access can quickly calculate the address. In addition, it can be embedded under the special mark pages dynamic web pages, that displays real-time data acquisition and control operations.