Homework 5: Theory of Operation and Hardware Design Narrative Due: Friday, February 15, at NOON

Transcription

1 Homework 5: Theory of Operation and Hardware Design Narrative Due: Friday, February 15, at NOON Team Code Name: _Agatha Group No. _4 Team Member Completing This Homework: _Eric Yee Address of Team Member: purdue.edu NOTE: This is the second in a series of four design component homework assignments, each of which is to be completed by one team member. The completed homework will count for 20% of the individual component of the team member s grade. The body of the report should be 3-5 pages, not including this cover page, references, attachments or appendices. Evaluation: SCORE DESCRIPTION Excellent among the best papers submitted for this assignment. Very few 10 corrections needed for version submitted in Final Report. Very good all requirements aptly met. Minor additions/corrections needed for 9 version submitted in Final Report. Good all requirements considered and addressed. Several noteworthy 8 additions/corrections needed for version submitted in Final Report. Average all requirements basically met, but some revisions in content should 7 be made for the version submitted in the Final Report. Marginal all requirements met at a nominal level. Significant revisions in 6 content should be made for the version submitted in the Final Report. Below the passing threshold major revisions required to meet report * requirements at a nominal level. Revise and resubmit. * Resubmissions are due within one week of the date of return, and will be awarded a score of 6 provided all report requirements have been met at a nominal level. Comments: Comments from the grader will be inserted here

2 1.0 Introduction Agatha will provide customers in a commerce center with specific, targeted advertisements based upon where they have shopped. Data will be collected using signals from RFID tags located in shopping bags. RFID tags will be read by a passive RFID reader located approximately ten to fifteen feet away from the main PCB board. The reader will communicate directly to Agatha s microcontroller using a SCI serial interface. The main PCB will contain the main microcontroller, which will use an algorithm to decide which visual image to display on a LCD screen. An external SD card will store advertising image data that interfaces through the SPI port, while the LCD screen will interface using the other SCI port. Both the RFID reader and LCD driver will need level shifters to communicate over the serial cable. This report will detail the operation of Agatha s hardware design, including a preliminary schematic. 2.0 Theory of Operation Agatha s hardware design is both simple and compact. At the heart of the design is the MC9S12NE64 microcontroller from Freescale. The RFID Reader and SLCD module each contain their own pre-packaged circuitry, which connect directly through an SCI interface to Agatha s microcontroller. These components were selected to simplify the hardware design. All of the main components on the schematic can operate safely at 3.3V [1]-[5]. Every one of Agatha s major components will interface directly with the microcontroller, including: a SD card reader, Ethernet connection, a level shifter, a RFID reader, and a LCD screen. How these components interact in Agatha s design is described below. 2.1 MCS12NE64 Microcontroller The MCS12NE64 microcontroller from Freescale will interface with every major component in Agatha s design. (See Appedix A for a block diagram.) How each part interfaces with the microcontroller will be discussed in each component s respected section below. In addition to interfacing with the different components, Agatha s microcontroller will use an algorithm to choose an advertising image to display based on information received from the RFID reader. It will also monitor the state of an external push button connected to a general I/O pin, which is used as a way for a consumer to interact with the display (e.g. display a map). This button will be located four feet from the microcontroller near the LCD screen and is optically -1-

3 isolated from the microcontroller due to its distance. An external crystal oscillator will provide a clock frequency of 25 MHz. According to Freescale s documentation, this clocking is needed to drive the Ethernet connection described in Section 2.3 [1]. This frequency is quick enough for all of the components, including the fastest component, the SLCD, which has a maximum baud rate of 115,200 (115,200 * 16 = 1.84MHz) [2]. The microcontroller will operate in Normal Chip mode with the internal voltage regulators activated. A power supply of 3.3V will power the chip, as well as all of the other components in the schematic [1]. 2.2 SD Card / Socket The SD card will store advertising image data on a flash SD card, as well as some user history data. Agatha s design team hopes to design a FAT file system so that image data can easily be added and removed from the card externally. The SD card s socket will interface through the SPI pins on the microcontroller, as well as two general purpose I/O pins. This operation will be discussed later in Section 3.0. The reader is safely powered by 3.3V [3]. 2.3 Ethernet amplifier Agatha plans to have Ethernet capability. This feature would allow stores to conveniently upload store and purchase data, as well as new advertising images. The microcontroller will directly interface with a high-speed LAN magnetic isolation module and a RJ45 Ethernet connector. The connection to the microcontroller features an array of capacitors and pull-up resistors to the 3.3V power rail. Freescale s suggested connections are summarized in Appendix B. 2.4 RS232 Level Shifters/Translators A level shifter is needed for the SLCD and RFID reader SCI serial connections. The chip can operate between a -0.3V and +6V range. Agatha s design will have the level shifter running at 3.3V to keep voltage on the board consistent. The MAX3322 can handle two different SCI serial communications, and its suggested connections are summarized in Appendix C [4]. -2-

4 2.5 RFID Tag Reader: connects to the HCS12NE64 through the SCI pins The TRRO1OEM RFID reader will read tags up to a 28 radius. Each tag s 64-bit identification will be relayed back to the microcontroller over the SCI serial line where it will be processed. The reader module comes on a pre-package board with two connection points: one connects to the serial data line and power inputs; the other connects to an 18 Round Antenna. (Note that this is a different model than was previously selected due to a lack of availability of the model. The new model is also from Intersoft and operates in the same manner. The only difference is that the antenna is no longer internally connected, but requires an external connection. The antenna, though long, is able to lie flat and still meets the thin profile desired for Agatha s design.) The RFID reader will run off a separate 12VDC regulated supply, sharing a common ground with the RS232 Level Shifter, as specified in Intersoft s documentation. The RFID reader uses a 9,600 baud rate, which can be easily handled by the microcontroller [5]. 2.6 LCD Display The SLCD is a stand-alone LCD driver module that will handle communications between the LCD screen and microcontroller. Image data will be sent to the SLCD module through the serial SCI pins of the microcontroller. From there, the chip will directly interface with the 5.7 LCD display that is integrated into the module. As mentioned in Section 2.4, a RS232 Level Shifter will be placed between the microcontroller and SLCD module. The SLCD is operable at both 5V and 3.3V. For simplicity reasons, Agatha will run the chip using the same 3.3V power rail as the microcontroller. The module will use the default speed of 9,600 baud, which is conveniently the same rate as the RFID reader [2]. 3.0 Hardware Design Narrative The remainder of this document will discuss the operations of the schematic design and will refer to the schematic in the OrCAD file submitted. The heart of the schematic is the MC9S12NE64 microcontroller. It will interface with the SPI port, onboard Ethernet, two SCI ports, and several I/O pins as seen in the block diagram in Appendix A. The most logical way to explain the microcontroller s operation is through the eyes of the end user. -3-

5 The process starts with the RFID reader, located approximately ten feet away from the main PCB board under a floor tile. If a user s tagged shopping bag passes within 28 of the reader, the reader will be able to read the tag s unique 64-bit identification number. The reader itself has prepackaged components already onboard to handle this processing. An external antenna attaches to a connection on the board and determines the reading range. The tag s identification number will be transmitted over a serial cable to a level shifter. This level shift will then transmit the signal safely into the microcontroller s SCI port pins. Similarly, commands can be sent to the RFID reader from the microcontroller to change modes of operation. As the reader natively interfaces with RS232, the SCI port on the microcontroller was an obvious design choice. Additionally, a store can upload shopping history data to the microcontroller through the onboard Ethernet port. Using LAN, this allows each Agatha kiosk to communicate to a main unit that can gather data and statistics for the commerce center or upload user data to the kiosk. The implementation will be up to the commerce center. In any case, Agatha s Ethernet connections to the standard RJ-45 connector were provided by Freescale, as seen in Appendix B. Using an internal algorithm on the microcontroller, Agatha will determine which advertisement to display for each particular user. Once a decision has been made, Agatha will communicate with the SD card to retrieve stored image data. Because of the need for a clocking signal, the SPI was the chosen port. Along with the clock, MISO, MOSI, and SS will interface with the Data Out, Data In, and Chip Select pins on the SD-Socket, respectively. In addition to the SPI port being used, two general I/O pins on the microcontroller are needed for the Write Protect (WP) and Chip Detect (CD) pins on the SD-Socket. Pins PG5 and PG6 on the microcontroller were chosen due to their relatively short distance to the SPI port pins [3]. The image data will be transferred through the microcontroller s second SCI port to a level shifter. This serial connection will connect to the SLCD module, which will accept the image data and buffer it to the 5.7 LCD screen integrated into the module. The SLCD runs through an RS-232 SCI interface and includes ample amounts of documentation. A push button near the LCD screen will allow the user to interact with the LCD display. A general purpose I/O pin, PG0, was chosen to keep all of the I/O pins organized close together on the microcontroller. Since this push button will be several feet away from the PCB board, it is optically isolated from the rest of the circuit. -4-

6 Status LED s fill the rest of the PG port pins (PG1-PG4) using them as general I/O s. For example, an LED may signal when a tag is read, when an image is selected, or when an image is being displayed. The use of these LED s will help with debugging and servicing the Agatha kiosk. Finally, an external crystal oscillator and the background debug headers are connected to the microcontroller. The values and arrangements of the passive components were suggested by the Freescale document in Appendix D and will meet the needs of the project. An external reset push button has been added for easy reset. 4.0 Summary Agatha s hardware design is compact and centralizes around the MC9S12NE64 microcontroller. The SPI port, both SCI ports, and the onboard Ethernet are all the peripherals utilized on the microcontroller. Conveniently, all of the components that will be located on the PCB board can safely run off 3.3V, eliminating the need for DC-DC or other converters [1]-[5]. Agatha s schematic follows many of the recommendations from the manufacturers, as seen below in the Appendixes. The design also includes status LED s to help with debugging and servicing the project. Agatha s hardware design meets all of the needs to perform to the team s specifications. -5-

7 List of References [1] Freescale Semiconductor, MC9S12NE64, [Online Document], 2004, [cited 28 January 2008], Available: MC9S12NE64FS.pdf. [2] Reach Technology, Inc., SLCD Controller Board, [Online Document], 2007, [cited 14 February 2008], Available: Manual v2.20.pdf. [3] 4UConn Technologies, SD-Socket, [Online Document], 26 July 2005, [cited 14 February 2008], Available: SD-Socket-PP pdf. [4] Maxim, MAX3322E/MAX3323E, [Online document], February 2003, [cited 14 February 2008], Available: [5] Intersoft Corp., WM-RO-LR, [Online document], February 2002, [cited 14 February 2008], Available: -6-

8 Appendix A: System Block Diagram Appendix B: Freescale suggested Ethernet Connection [1] -7-

9 Appendix C: Maxim MAX3322 suggested configuration [4] Appendix D: Freescale suggested configuration (80 pin TQFP) [1] -8-