Project Analog - March 2008 - (Page 19)

typically, each node in a CAN system must have a device to convert the digital signals generated by a CAN controller to signals suitable for transmission over the bus cabling. consequence to the operation and reliability of the system. An example of a single node for a CAN network is shown in Figure 2. In this diagram, pressure is measured using a pressure sensor. The differential output voltage of this sensor is gained by a discrete instrumentation amplifier and filtered by a fourth order, low pass, active filter. The signal is then converted to a digital code with a 12-bit A/D converter, mcP3201. The receiving microcontroller sends the data to the CAN controller. The common language between the nodes is generated and maintained by the CAN controller and the voltage compliance to the network is managed by the CAN driver. Each node in a CAN network can perform a unique function. Although Figure 2 illustrates a pressuresensing system, other types of systems can complement your application. Additionally, this block diagram of a CAN node can be implemented in a variety of ways. For instance, in the initial build, the microcontroller could have the CAN controller integrated on-chip. At a later date, nodes can easily be added with minimal software impact. When you are ready to add, enhance or build a small stand-alone network, the combination of an MCP2515 with a simple microcontroller would be a good choice. The MCP2515 stand-alone CAN controller implements version 2.0B of the CAN specification. It is capable of transmitting and receiving both standard and extended data and remote frames. The MCP2515 has two acceptance masks and six acceptance filters that are used to remove unwanted messages. The 4-wire interface between the MCP2515 and the controller is SPI™. The MCU pins used for SPI can be recovered if the MCP2515 RXnBF pins are configured as GP output and the TXnRTS pins are configured as GP input. Typically, each node in a CAN system must have a device to convert the digital signals generated by a CAN controller to signals suitable for transmission over the bus cabling. The device also provides a buffer between the CAN controller and the high-voltage spikes that can be generated on the CANbus by outside sources (EMI, ESD, electrical transients, etc.). The MCP2551 highspeed CAN, fault-tolerant device provides the interface between a CAN protocol controller and the physical bus. The mcP2551 has differential transmit and receive capability for the CAN protocol controller and is fully compatible with the ISO-11898 standard, including 24V requirements. It will also operate at speeds of up to 1 Mbits/sec. This serial communications protocol supports distributed real-time control with a sophisticated level of security. The CANbus time-proven performance ensures predictable error-free communications for safetyconscious application environments. It is able, through arbitration, to prioritize messages. The configuration is flexible at the hardware, as well as the data link layer, where many of the transmission details can be modified by the designer. This is done, while at the same time there is system-wide data consistency. Contents Viewpoint Wireless Communication Using IrDA® Wireless Design Choices Advanced Communication Solutions for Lighting Analog news Microchip analog page Interface products overview Sample center microchipDIRECT Reference designs/ app notes Technical training • 19 · ProjeCt ANALog · mAr 08 http://www.microchip.com http://www.microchip.com/analog http://www.microchip.com/analog http://www.microchip.com/interface http://www.microchip.com/interface http://sample.microchip.com/Default.aspx?testCookies=true http://www.microchipdirect.com/catalogselection.aspx?returnURL=default.aspx http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1423

Table of Contents Feed for the Digital Edition of Project Analog - March 2008

Project Analog - March 2008 Contents Viewpoint About Project Analog Sponsor Wireless Communication Using the IrDA® Standard Protocol Wireless Design Choices Advanced Communication Solutions for Lighting Putting 10-GbE PHY Options Into Perspective Ease Into the Flexible CANbus Network Technology and Drivers for Mobile WiMAX Analog News—Analog News from Multiple Sources Enter to Win an iPhone Contact Project Analog Sponsor Treelink Microchip Advanced Parts Selector (MAPS)

Project Analog - March 2008

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