January 2012 Archive

Microcontroller-based circuit design of four BCD encoder 0

1 Introduction

bcd code, also known as b / decimal code, a binary coded decimal code, design, digital circuit testing process, or the face of the hardware interface IC with bcd code, often want to easily and quickly generate bcd code to complete the current work, test the correctness of hardware circuits, such as PLL Frequency Synthesizer IC mc145163p with four bcd encoder interface for setting the loop n divider, through the completion of this article describes the production of bcd generator can provide 4 bit bcd code output, easy to control the output of each bcd, bcd coding can quickly get the completion of the test or received encoded output bcd bcd encoder interface IC, without frequent jumpers.

In addition, bcd coding with 8421 yards, 2421 yards, and other forms of more than three yards, 8421 yards this paper, a common implementation of an example circuit and program preparation. If a slightly modified version of the program can easily implement other types of encoding (such as 2421 yards). The circuit is designed to at89c2051 core 4 × 4 matrix keyboard (s0-s15), so just press the appropriate key on the keyboard (s0-s9) that can generate a corresponding (decimal 0-9) of the bcd code , by setting the toggle button (s10-s13) are free to control the four in any one, during the show in real time with a digital code corresponding to the current bcd decimal.

Circuit functions and features:

4 bcd encoded output, use of MCU port lines can be extended digits.

Change the software key number 0 – 9 number keys (ie, the corresponding function s0-s9) of the program can achieve other encoding forms (such as 2421 yards). See the software section.

Circuitry used 8421 yards, for example, and a digital display corresponding decimal number (can be omitted).

Complete 4 × 4 matrix keyboard scan program execution, the application can be ported to other circuits.

bcd coding for signal latched by the latch, and leads to interfaces to connect other circuit.

“Position” control and 0-9 encoded output independently of each other, press the function key you can directly obtain the required bcd coding output and the “median” choice.

2 circuit diagram

Circuit diagram shown in Figure 1.

3 Circuit Analysis

at89c2051 the p1 port 4 × 4 matrix composed of the keyboard (s0-s15), which p1.0-p1.3 as a line of wire, p1.4-p1.7 as a column line, designed keyboard scanner can achieve pre-conceived function ( See software design section). Press s0-s9 can produce 0-9 decimal code number corresponding to the bcd, s10-s13 for four bcd code switching button, s14, s15 yet to use, you can not install, p3.3-p3.0 is bcd code data output lines can be seen from the circuit, because the function of the keyboard and output to achieve four bcd coding, apparently p3.3-p3.0 and the same time as the data bus connected to the 4 d latch (4042), by s10-s13 to switch, latch for 4 d (u3-u6) only one time while the p3.3-p3.0 valid data “read” and then latched. In fact s10-s13 control p3.4 and p3.5 state (p3.4 and p3.5 four combinations) and by 2-4 line decoder (u2; 74ls139) corresponding u3-u6 be effective signal, Table 1 s10-s13 control state corresponding to each chip, we can see, u3-u6 in any one (for example, u3) is active and “read” p3.3-p3.0 data, the rest of the (u4 / u5/u6) in the latch state, to retain the original data, so users can change in any one of the desired bcd code output.

u2 (74ls139) is a 2-4 line decoder functions in Table 1, and his input b, a respectively connected to p3.4, p3.5, output y0-y3 depend on the input side, each one where only one output (y0-y3) to active-low output. u3-u6 is d latch, is one of the main 5 feet and 6 feet of the relationship determine their work status, access to information that, when 5 feet and 6 feet logic potential is the same, the chip can output data to d3-d0 to q3-q0; 5 feet and 6 feet when the logic is not the same potential, the chip is latched state of the original data, but not “read into” the current d3-d0 data circuits to u3-u6 6 feet fixed then low, and 5 feet respectively u2 (74ls139) of the output signal to control, it is easy to achieve, “you can achieve alone bcd code set.” 4511 is a decoder driver, then the common cathode LED displays the current corresponding to each of the bcd decimal code number to facilitate the observation, shows some very simple, not repeat them here, at the same time, show some of the circuit is not required, can be omitted , bcd code leads by j3 and j2, the reason for using two linker is to be more flexible and easy to use.

4 Software Design

Treatment is to achieve the main keyboard, the program must confirm which one button is pressed, then go to the appropriate handler execution, in fact, the program is a complete keyboard scanner, if the changes which the subroutine can apply to other control circuit, the following description with detailed procedures and for reference, Figure 2 is a flow chart.

Keyboard scanner simply, it is the task: First, to confirm whether there is button pressed, then scan to determine which line to get the key in the final 4 by comparing the pre-set line of table lookup and calculated specific key to turn procedures to the appropriate function.

(1) set out lines for the input state (p1.4-p1.7 1), line-line (p1.0-p1.3) the first is 0, that is set equal to f0h and p1.7-p1.0

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80C51 microcontroller C8051F020 and the similarities and differences

1 Introduction

80c51 MCU and its derivatives in China and around the world access to a very wide range of applications. Chip area most of the staff are familiar with 80c51 microcontroller, the tertiary institutions are using 80c51 microcontroller series as a teaching model. With the continuous development of the microcontroller on the market there have been many high-speed, high performance new single-chip, based on the standard 8051 microcontroller core is facing out of the market situation. To this end, some of the traditional semiconductor companies began construction of the big 8051, mainly to improve speed and increase the on-chip analog and digital peripherals, with a view to significantly improve the overall performance of the microcontroller. Which the United States launched the c8051f cygnal MCU family of microcontrollers from the 80c51 mcu soc era into the era, making the 8051-core microcontroller to a new level.

c8051f MCU is a fully integrated mixed-signal system-on-chip with 8051-compatible microcontroller core cip-51, employs a pipelined architecture, single-cycle instruction execution speed is 12 times 8051, all the original instruction set running speed is 9.5 times. Familiar with ncs-51 Series MCU engineers and technicians can easily grasp c8051f application technology and software can be transplanted. But 8051 can not be used in the procedure of copying c8051f microcontroller, this is because the two there is a big difference between internal resources, must be processed to be used. Which c8051f020 its functions more comprehensive, broader application of the characteristics of a representative c8051f products, its cost performance in the current applications are also very competitive. c8051f020 internal circuitry including cip-51 microcontroller core and the ram, rom, i / o ports, timer / counters, adc, dac, pca, spi and smbus and other components, that is the basic unit of the computer as well as analog and digital peripherals located in a single chip to form a complete system on chip (soc). This article will introduce c8051f020 similarities and differences between the microcontroller and 80c51 (mainly differences) and beginners programming issues that need attention, and gives developers tools through cygnal ide debugging environment software verification of the source.

2 the same point

c8051f020 microcontroller and 80c51 microcontroller family instruction set exactly the same. Master 80c51 microcontroller can easily accept the c8051f020 to complete the application of appropriate technology and software portability.

3 main hardware differences

3.1 speed

c8051f020 command speed is generally 80c51 MCU more than 10 times. Because it cip-51 in the pipelined processing architecture, the machine cycle has no timing, the execution of the smallest units of the system clock timing, most of the command system as long as 1 to 2 cycles to complete. Also, because the clock system more perfect than the 80c51, there are multiple clock sources, and a programmable clock source, the clock frequency range of 0 ~ 25 mhz, when the cip-5l’s maximum system clock frequency of 25 mhz, its peak velocity up to 25 mi / s, c8051f020 has entered the ranks of single-chip 8-bit high speed.

3.2 i / o port configuration

c8051f020 has eight 8-bit i / o ports, connections and a significant reduction in the external expansion devices, will help improve the reliability and performance. The low four i / o ports except as a general common i / o ports, but also other functional modules as input or output pin, it is through the cross switch configuration register xbr0, xbr1, xbr2 (you name and format shown in Table 1) select and control, they control the priority decoder selector switch circuit shown in Figure 1 can be on-chip counter / timers, serial buses, HW interrupts, comparator output, and other digital signal is configured to port i / o pin there, so the user can choose according to their specific needs and resources required for universal digital i / o port. Digital Crossbar is a relatively large digital switching network, which in all 80c51 MCU is a blank. In addition p1mdin used to select the input mode is p1 analog input or digital input, reset the value 11111111b, which is the default mode for the digital input. And 80c51 microcontroller i / o pin assignment is fixed, that is occupied by more than pins, configuration, and not flexible enough.

c8051f020 through the Priority Crossbar Decoder (Figure 2) control digital switching network, the port pin assignments in order from the beginning until p0.0 p3.7. When the cross-switch configuration register xbr0, xbr1 and xbr2 in the corresponding peripheral enable bit is set to logic “1″, the cross-switch port pin assigned to a peripheral, for example, if uartoen bit (xbr0.2) is set to logic “1″, tx0 and rx0 pin will be assigned to the p0.0 and p0.1. Because uart0 has the highest priority, so when uartoen bit is set to logic “1″ when the pin will always be assigned to the p0.0 and p0.1. Distribution of cross-switch is not set as a general-purpose port i / o port. Note: When you select the serial communication peripherals (ie, smbus, spi or uart), the cross-correlation function for all distribution switch pin. For example, can not uart

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Microcontroller application in power supply design

microchip’s Security, Microcontroller and Technology Development Division Application Engineer justin milks

manufacturer power supply designers often face all kinds of mutually exclusive requirements. On the one hand to reduce size and cost, and we want to provide more functionality and improve the output power. Limited by the principle, analog power supply itself has limited functionality, while the analog power supply controller design is more complex. For this reason, some designers turn to a pure digital power supply design. However, for many designers, so quickly to the unfamiliar areas is not easy. A compromise more feasible approach is to use traditional analog power supply, but increased as the number of single-chip front-end.

This design has the advantage of controlling the power supply itself is still using analog techniques. Therefore, power supply designers need to start from scratch all-digital design that existing designs can add new features. With this approach, the design is still using the familiar error amplifier, current detection and voltage detection circuit. Of course, although some design elements (such as the compensation network) still using discrete devices, but the rest is controlled by the microcontroller.

SCM can bring the functionality can be divided into four groups: control, monitoring, to determine sexual function and communication. Below we will discuss these types of functions.

The first control functions and the microcontroller and the hardware interface between the power supply. In analog design, very important to be left to connect the microcontroller interface. Some of the internal power supply controller generates control signals (such as the reference voltage). This single-chip controller for the external connection points provide very little. microchip company mcp1630 power controller is designed for the microcontroller provides a wealth of connections. As of this writing, we assume that the power controller provides two control points – shutdown input and the ability to set the reference voltage, shown in Figure 1. Although this does not look more than two connection points, but has been able to provide a very powerful and complex control functions.

Currently, single-chip power supply designs in a number of main function is to monitor. Many microcontrollers have on-chip analog to digital converter (adc) and analog comparators. Therefore, the microcontroller in the monitoring of the input voltage, input current, output voltage, output voltage and temperature signals are ideal.

Such a broad range of microcontroller to monitor the signal, you can do more functions, such as intelligent fault detection. Single-chip multi-functional due to its programmability, can be easily customized to meet the design requirements. Thus, the classification of fault conditions can be handled. Transient over-current and other non-critical failure may only need to set a flag on it. Overheating such a failure may need to turn off the power until troubleshooting. Need to restart the power supply failure can also be more strictly controlled. In a period of time if there are too many failures, the microcontroller can permanently turn off the power.

Single-chip processing power for complex calculations can also be measured, such as the power of real-time calculation. In analog systems, power value to determine the need for complex simulation. But for the chip is just a trivial matter. Input power, output power, efficiency and power loss and other parameters can be calculated.

Finally, the chip can also support the monitoring function of the more advanced features, such as failure prediction. The current real-time and historical data for comparison, power supply designers can determine the cause of power failure conditions. Power itself has the ability to predict their failure to provide cost savings and higher reliability.

Monitoring data and not only for fault detection. Based on these data can also take many other actions. These tasks will fall to determine the scope of sexual function. Allows to determine the nature of the design to increase power supply designers greater flexibility, more functionality and protection capabilities. Let us consider the soft-start or undervoltage lockout situation. Single-chip computer to complete these tasks, locking and soft start voltage ramp rate are programmable, and does not rely on analog devices.

Determine the sexual function can also perform more complex tasks. Such as power-on sequence. Another can be programmed to monitor the power supply voltage until the monitored voltage reaches the set value and then start. May also have such a situation, the two voltages must be proportional to the increase, or follow the changes to each other. All of these features can be achieved only modify the software without having to make hardware changes.

Another judge sexual function may be applied to adjust the current based on temperature limit. This power supply designers can use the device temperature derating parameters to ensure reliable operation.

Used to determine sexual function can also compensate for the device to improve its accuracy. Many data sheets are given parameters with temperature changes. In this case, the microcontroller can be used for temperature compensation. In this way, designers can use lower-cost devices, and the results according to the temperature compensation

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AT89C51 in the application of wireless data transmission

A system composed of

System components as shown in Figure 1, Figure 2 shows

System consists of measuring stations and the master control station of two parts. Mainly done on-site measuring stations signal acquisition, storage, receiving remote control commands and send data. Master station’s main job is to send remote commands, receive data, data processing and data management, display and print random.

2 at89c51 serial communications and digital radio

at89c51 atmel chip companies, is a low-power, high performance, with 4kb flash rom chip 8-bit cmos microcontrollers, operating voltage range of 2.7 ~ 6v (the actual use of +5 v power supply), 8-bit data bus. It has a programmable full-duplex serial communication interface that can simultaneously send and persistent serial collection. By rxd pin (serial data receiver) and txd pin (serial data transmitter) to communicate with the outside world.

2.1 communication protocol and baud rate

Digital radio and the microcontroller, the communications protocol for the main computer terminal:

Communication interface – standard serial rs232 interface, 9-wire half-duplex mode;

Communication frame format – a start bit, 8 data bits, a programmable data bits, 1 stop bit;

Baud Rate – 1200 baud.

Digital radio use motorola’s gm series car radio, working at vhf / uhf frequency bands, wireless data transmission (standard 9-wire serial rs232 interface), but also for voice communication; using binary frequency shift keying (2fsk) modulation demodulation method, in line with CCITT ccitt.23 standards. In the case of digital transmission band, it is recommended no more than 1200b / s data rate used. Actual use, the work in the 220 ~ 240mhz radio frequency range, using half-duplex mode (perform the sending and receiving operations, but not both simultaneously) to meet the system requirements.

2.2 at89c51 serial port work

at89c51 serial port can be set to four operating modes, can have 8-bit, 10-bit and 11-bit frame format. This system, at89c51 serial port in Mode 3, the frame 11 Min asynchronous communication format: 1 start bit, 8 data bits (LSB first), a programmable data bits, 1 stop bit .

Before it is sent by software to set the 9th bit (tb8) for the parity bit, the data will be sent written sbuf, initiates the transmission. The serial port can automatically tb8 out, the data is loaded into the 9th position, and then send out one by one. Been sent, so that ti = 1.

Reception, set scon in the ren to 1 to allow reception. When detected rxd (p3.0 end with “1″ to “0″ transition (start bit), the starting receive 9-bit data into the shift register (9) When satisfied ri = 0 and sm2 = 0 or the received 9th data bit is 1, the first 8-bit data into sbuf, 9-bit data scon in rb8, set ri to 1; otherwise, the receiver is invalid, does not set ri.

Serial port baud rate from the Timer 3 overflow rate and smod t1 values also decided:

Overflow mode 3 baud rate = t1 / n

When smod = 0 时, n = 32; smod = 1 时, n = 16. t1 t1 overflow rate depends on the count rate (count rate = fosc/12) and ti preset initial value.

Timer t1 for baud rate generator in Mode 2 (auto reload the initial value). Set th1 and tl1 timer counter initial value x, then every “2 8-x” machine cycles, t1 time-out occurs. Initial value of x is determined as follows:

x = 256-fosc × (smod +1) / 384 × btl

This system, smod = 0, wave line rate btl = 1200, crystal fosc = 6mhz, so the initial value x = f3h.

2.3 at89c51 hardware connections and digital radio

at89c51 and digital radio hardware connection shown in Figure 3.

Asynchronous serial communication system using transmission measurements. The use of single-chip digital radio with rs232 serial data port connected. Normality as the receiving state radio (ppt = 0, closing state; ppt = 1, the state issued), the microcontroller p3.5 pin output high. Microcontroller ttl level rs232 level using radio, done by the max232 ttl level rs232 level with the conversion between. 3 optical coupler 6n137 MCU and radio isolation between the power supply, enhancing system robustness.

Controlled by the microcontroller with the door side of the tri-state buffer 74hc125, non-controlled radio transceiver door 74hc14 conversion, and to receive instructions and data transmission. Reception, p3.5 = 1, c2 = 1,74 hc125b deadline; p3.5 by 74hc14 inverter, optical isolation, the radio ppt pin is low, set to receive its state; while c1 = 0,74 hc125a guide pass, to receive instruction from the radio rxd-ended input, the max232 level-shifting, optical isolation, 74hc125a buffer gate, into the microcontroller rxd pin. Launch, p3.5 = 0, by the 74hc14 inverter, optical isolation, the radio ppt feet high, set to launch its state; while c1 = 1,74 hc125a end, c2 = 0,74 hc125b conduction, data txd pin output by the microcontroller, the 74hc125b buffer gate, optical isolation, max232 level change, through radio txd port to send data out.

3 Communication Software Design

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Monitoring network design in the application of programmable

Author: Wholesale Zhu Yaodong

Huan-Chun Zhang Ya-Zhi

Yancheng Institute of Electrical Engineering (224003) Yellow Mountain steady source: “Electronic Technology”

Abstract: A programmable single-chip system in the application design. The design is simple, mature technology, suitable for nuclear cisc structure based on 8051 microcontroller system. Detailed implementation of the program and cited Chi program and PC software design.

Keywords: serial communication

In-Application Programmable (iap) mcu

Replacement of electronic products faster and faster, how to shorten design time, rapid introduction of products, reduce design costs and improve overall system performance is every designer issues of common concern. Called in the application of programmable (in

application programming-iap) design came into being, it can be in the field (when the original code is running there) run to re-write the code. The advantage of this program is to reduce development time code can be tested and modified products on the assembly line, the code can correct errors in the field, you can easily add new product features or to upgrade the system remotely. Currently, to achieve in the application of programmable general there are two methods: one is to use single-chip package with a dedicated chip; the other is the support of the application using the new programmable microcontroller. This paper describes a microcontroller based at89c51 programmable design in the application, it only take at89c51 the uart, just a few a few chips will be able to achieve the above functions. Particularly useful for communicating with the uart control network design.

1 design ideas

Based on the 8051 microcontroller core provides two separate address spaces, one for program memory and one for data storage. This special structure of the address is not in any case writes the data to program space, data protection code will not be covered, but this feature allows the MCU can not be achieved in the application programmable. If you use a method of “cheating” system to make error that the program memory is data memory, program memory can be written to the data. “Cheat” the system is temporarily in the program memory iap “reclassified” as the data space, rather than program space, and then after the completion of the iap it reclassified as program space. Such programs need not only can be used as a memory but as the program memory data storage. Now available in a variety of power-off protection function of both SRAM data memory read and write speed but also has a high non-volatile program memory. Such as dallas’s ds1230y-70 is pin-compatible with the common ram27256, embedded non-volatile memory to protect lithium battery, read and write speeds of 70ns, power-down state data can be saved for 10 years.

Designed in accordance with this line of thinking ability in the application of programmable microcontroller system block diagram shown in Figure 1. The system has the following characteristics: (1) three ram, which ram3 is the data memory, rama, ramb both data memory and a process memory, rama and ramb using ds1230y-70 static ram. rama and ramb have the same address, when one piece as a program memory, the other one is the data memory. at89c51 data space and address space separate from the memory feature ensures that no two conflicts. (2) increase the selection circuit, used to program memory and data memory “reclassified”, by dn_con control signal lines to choose wr Dou Dou psen signal or signals into the corresponding static ram. (3) increase the serial eeprom to save important information, such as model number and download signs.

at89c51 with 4k on-chip flash memory, can store the boot program. System initialization, the serial port interrupt the boot process and other procedures as cured in at89c51 flash memory, while the main program on the 32kb of static ram memory. Therefore, the system program memory address space from 0000h ~ 03ffh and 8000h ~ 0ffffh. The data memory address from 0000h ~ 0ffffh, shown in Figure 2. Serial port interrupt the boot process will be the highest priority is set to no class, program code is received when at89c51 download command, the data will be 8000h ~ 0fffh space then write the code. When the end of the application code, change dn_con control signal to the original data memory into program memory, while the original program memory into data memory. When the serial interrupt service routine, the stack pointer to the serial interrupt return 8000h, and exit the interrupt, so the program jump to 8000h run the downloaded program code. Figure 2 serial eeprom i2c bus based on the 24c01 chip to store some of the key data, plus monitoring and control module station number, download signs.

2 Select the circuit implementation

Select the circuit shown in Figure 3, 74hc157 a second election is four chips. When p1.0 (dn_con) is low, a = y, then rama of rd pick

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MCU read of CF card

Abstract: cf card is included for the control and the standard large-capacity flash memory devices, high capacity, small size, high performance, easy to carry, etc., have been widely used in data acquisition systems and many electronic products in the message. This paper describes the cf card in the SCM system’s hardware interface circuits, and microcontroller cf card reader to achieve the standard files, and files can be written to the windows operating system to read and write. Keywords: cf card chip fat file format Introduction Since cf card (compact flash card) with a large capacity, small size, high performance, easy to carry, etc., and read and write speed, with a variety of computer operating system platform compatible, so In the data acquisition system and data recording or data transfer between pc machine to use more memory cf card. In order to pc machine is convenient for data processing, the next bit-side to adopt a standard format for organizing data, in which data is written in accordance with standard file format for windows, through a card reader in the pc-side content will be written cf read a standard file format. windows standard file format fat, fat32 and ntfs. Taking into account the widespread use of windows 98 system cf card capacity and other factors, usually fat (file allocation table) file system. SCM system cf card reader, it is directly from the underlying operations, including address, create a file and read and write. About 1 cf card cf card integrated controller, flash memory array and read-write buffer, shown in Figure 1. Built-in intelligent controller, designed to greatly simplify the external circuit, and full compliance with pc-International Federation of the memory card pcmcia (personal computer memory card international association) and ata (advanced technology attachment) interface specification. In fact, the controller plays the role of a protocol conversion, is about to translate into flash memory read and write access to the controller, so that different cf cards can be a single body to read and write, without worrying about compatibility the problem. buffer structure cf card, cf card, making communication with external devices at the same time, cf card, flash chip controller can read and write. This design can increase the reliability cf card data reading and writing, while increasing the data transfer rate. cf card supports multiple interfaces to access mode, in compliance with pcmcia standard memory mapped mode, i / o card mode and meet the specifications of the true ide ata mode. On power, oe (9 feet) is low, cf card into the true ide mode, then pin oe also called ata sel; on power, oe (9 feet) high, cf card into the pcmcia mode , that is memory mapped mode or i / o card mode, then you can register by modifying the configuration options into the corresponding mode. Configuration Option Register format is as follows: sreset levelreq conf5 conf4 conf3 conf2 conf1 conf0 sreset-soft reset signal; level req-interrupt mode selection (level or edge). For example, to add memory mapped mode, you only need to ensure that the power-oe is high, because the configuration option register conf5 ~ conf0 bit initialization value of “00000″; and to enter the i / o card mode, In addition to the power to ensure that oe is high, but also further set conf5 ~ conf0, as listed in Table 1. But for specific types of cf card, the following three conditions is being cfa (cf card association) allowed: ① the power to enter the true ide mode, work process, as long as the monitor into a high-oe, true on exit ide mode; ② allows the card to re-reset the configuration; ③ into the pcmcia mode on power, allowing the process, as long as the monitor into a low-oe, enters the true ide mode. Table 1 Mode 2 cf card cf card 51 microcontroller interface mode and 51 in pc memory chip interface circuit shown in Figure 2. As a result cf card into the memory automatically after power mode, but there is no register read and write on the properties, it can be reg then high. Chip select signal ce1 and ce2 optional combination of data bit width, as listed in Table 2. Figure 2 ce2 then vcc, use the 8-bit (d7 ~ d0) data width. Table 2 Data width of the selection in order to achieve plug and play functionality, ce card provides two cards to detect the presence of the pin (cd1, cd2), the card inside the ground. When the host detects the connected two pins both cd1 and cd2 is low, it can determine the card connected to the host; otherwise, the card is not connected to the host. Since i / o port tension, rdy / bsy pin is left unused, by querying the status register to determine the cf card is ready. In practice, due to read and write at least once a sector of 512 bytes, so expansion of a ram. We use the 62256 capacity of 32kb, so that we can support large 2gb cf card (see below), to increase its scalability. 3 fat is the fat file system file system, dos based file system. Often said fat12 fat 12-bit and 16-bit fat16, the other is 32-bit fat32. Taking into account the limited capacity cf card, should use fat16. Here only the fat file system to make a brief introduction, more details see references. Addressing the disk in two ways: physical address c / h / s (cylinder / head / sector) approach and the logic block lba (logical block addressing) addressing. Conversion relationship between the two: lba address = (number × heads, cylinder + head number) × the number of sectors the number of sectors -1 + lba addressing modes used, there is no head and track the conversion operation, continuous access sector, the operating speed faster than physical addressing, but also simplifies access to the disk. Structure and layout of the hard disk is divided into mbr (master boot sector) and up to four logical partitions (including the non-dos partition partition dos), and in the dos logical partition the disk is organized as follows: boot sector dbr (dos boot record): at lba 0 sector, including jumps, vendor identification and the dos version number

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AT88RF256 RF card reader design

Source: light fixtures Author: Beijing Jiaotong University Dong Xinyu Wang Zhanguo Li Xingchun

Abstract: The use of Beijing Xing Wei Limu Company at-rfmod06 series of radio base station modules with pic16 microcontroller-based development for 125 khz frequency of at88rf256 RF card reader. Focuses on the hardware module to connect the base station and base station on the radio how to read and write control card, and the corresponding applications.

Keywords: RF card reader; at88rf256; pic microcontroller; design

1 Introduction

With the computer and embedded system development, ic card has been integrated into people’s daily lives and develop into several categories, including, non-contact ic card caused the emergence of particular concern. Are non-contact RF card ic card, ic card, it avoids the common and the physical contact between the reader, reducing the wear of the card, it has been widely welcomed. RF is radio frequency identification cards (rfid) component of the system.

RFID (radio frequency identification, to f referred rfid) technology is the rise of the 1990s, an automatic identification technology. It uses radio frequency non-contact way of two-way communication and exchange of data, in order to achieve identification purposes. A typical system consists of rfid tags (tag), reader (read / write device) and data exchange and management system, etc. Tag, also known as radio frequency card, with the intelligent reader and encrypted communications.

2 system working principle and hardware design

I designed the RF system consists of a computer card reader, card reader and RF components, system architecture shown in Figure 1.

2.1 RF Card Reader

RF card reader mainly by picl6 type microcontroller and Beijing Weili Mu Xing produced at-rfmodcl6 series of radio base station modules. The module uses a common u2270b type non-contact card reader base station circuit. By the integrated circuit chip power supply, oscillator and coil actuator composed of energy transmission lines, used to power radio cards work; also incorporates signal amplification and antenna driver circuit to complete the card with the radio signal between the sending and receiving . at-rfmod06 with picl6 interface circuit shown in Figure 2.

af-rfmod06 module pin functions as shown in Table 1. The module uses a separate 9-pin package, the internal integration of the clock, RF, filtering, amplification, modulation and demodulation and other analog circuits, in accordance with Figure 2 digital interface circuits connected, simply select the appropriate antenna and the resonant capacitor can be complete RF circuit design.

In Figure 2, the base station antenna and the oscillator capacitor formed lc oscillator circuit, the oscillation frequency of the system requirements have limited 125 khz (± 5%), the antenna can reach a maximum oscillation amplitude 120 v, generally not greater than 80 v, can and antenna coil through a resistor in series to adjust the antenna’s oscillation amplitude. Oscillation capacitor voltage value should be greater than 100 v. After repeated testing, parameter is set to c = 2 200 df, l = 680μ h. r = 82ω.

2.2 at88rf256 RF card

at88rf256-12 atmel card is U.S. based company introduced a 125 khz frequency proximity cards can be encrypted. The amount of data is 256 bits. As a typical low-frequency, encryption, and can read and write cards. at88rf256 a 12 on the market have a wide range of applications. at88rf256-12 from the circuit and coils. Internal structure of the circuit shown in Figure 3.

L1 and l2 circuit pin connector pin and the coil, the coil inductance of 10.1 mh, the card operates at 125 khz. Its work by the on-chip power circuit built-in capacitance of the coil and lc oscillator power storage available. at88rf 256-12 design of the capacitor built into the circuit, reducing the card processing chain. But also improves the module into the card and the yield and reliability. lc oscillations generated by the card’s power supply circuit transformed respectively to control part and eeprom unit.

3 codec and software process

3.1 RF card and command register

The eeprom is divided into lo-card page. Including 32 per page, its contents are shown in Table 2

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LPC3180 ARM9 microcontroller hardware and software platform

Source: Microcontroller and Embedded Systems Author: Beijing University of Aeronautics Bai Junjie Zhao Qi Wang Peng Peng Philips Semiconductors

Summary of the philips lpc3180 microcontroller embedded software and hardware platform as the core design; part of the system hardware and software design part of a detailed analysis, and for lpc3180 chip features focused on building its software and system boot process. Experimental results show that, lpc3180 chip embedded system platform with hardware floating-point unit, a high-performance floating-point processing capabilities to meet the complex requirements of embedded applications.

Keywords lpc3180 arm9 hardware and software platform

Embedded system design including the hardware platform and software platform in two parts. The former is embedded microcontroller / microprocessor core hardware system; the latter is built around an embedded operating system software. Both in the design are inextricably linked, and the need to optimize the design trade-offs between, depending on the application for external expansion and cutting.

Based on arm926ejs kernel lpc3180 rich integrated peripheral resources to build an embedded system design provides a great space. In this paper, I develop lpc3180 embedded platform experience, will introduce the system to achieve specific, composition and experimental results.

1 lpc3180 chip features introduced

lpc3180 is philips company introduced a new arm9 microcontroller. It uses 90nm process technology, chip integration arm9ejs processor core, with high computational performance, low power consumption, which makes a lot of power-sensitive embedded applications arm9 can still use high-performance microcontrollers. lpc3180 core normal working voltage of 1.2v, the low power mode can be reduced to 0.9 v; the same time, lpc3180 as a new 32-bit microcontrollers, the new features include:

◆ on-chip integrated vector floating point (vfp) coprocessor. lpc3180 floating-point unit has three separate lines, support for parallel single-precision or double-precision floating-point add / subtract, multiply / divide and multiply accumulate operations, fully compatible with ieee754 standard for high-speed floating-point applications.

◆ on-chip integrated usb otg control module, supports and portable usb or usb peripherals connected to the master device can be used with pda, card readers and printers and other devices directly connected to pc machine without intervention.

◆ lpc3180 using multilayer ahb bus system, for each main module provides independent buses, including the cpu instruction bus and data bus, data bus, two sets of dma controller and 1 usb controller data bus set.

lpc3180 internal structure shown in Figure 1.

Internal structure of Figure 1 lpc3180

lpc3180 Other features include: integrated mlc / slcnand controller, sdr / ddr sdram controller, sd card interface, uart, spi, i2c peripheral communication modules, and high-speed / ms timer, rtc, watchdog timer, 10 adc and other functional modules.

2 hardware platform

To lpc3180 hardware platform as the core of the design framework shown in Figure 2.

Figure 2 lpc3180 block diagram of the hardware platform

(1) Memory System

nand flash memory. By lpc3180 internal integrated mlc / slc nand direct external controller or single-stage multi-level nand flash devices. The system chosen st nand256r3a, its 32 mb storage space to meet the storage system boot procedures, embedded operating system kernel and file system size requirements.

sdram memory. System used two 16 micron sdram, sdram memory parallel build 32-bit system. 32 mb sdram space to meet the embedded operating system, and the upper application of operational requirements.

sd card slot. Within the integrated system through lpc3180 sd card interface, providing sd card slot for sd memory card storage expansion, as an external storage space.

(2) external communication interface

uart interface. lpc3180 uart module within the integrated standard and high-speed uart module 550 in line with industry standards. Outside the system to expand the uart1 / 7, uart2 and uart5, used to implement the base

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Intelligent two-way digital signal

Author: product catalogs

Laboratory sources are generally used with the analog circuit to generate the signal used. Analog circuit has some inevitable shortcomings, such as inconvenient to use, dysfunction, low resolution, expensive and so on. With the MCU digital signal source with easy to use, powerful, cost-effective features. This project uses the MCU, inherited the general advantages of digital signal sources, in particular, there is provided a dual-frequency difference with the output signal, in order to meet the actual needs of laboratories and factories.

A hardware circuit description

The system uses the bus structure, cpu for the 8031, plug a 2718ram, 4 × 4 matrix keyboard to keyboard buffer with 8031 by 244 Connect, the decoder 138 is responsible for providing addresses to each terminal, the output terminal and a chip-chip select terminal is connected. 4 LEDs, respectively, power, sine, cosine, ramp, hanging by the latch 373 on the bus. icm7212am for the led display decoder driver chip, drive and maintain the function of decoding. Can drive four common anode 7-segment, and the brightness can be adjusted. dac0832 for the 8-bit d / a converter, there are two non-latching, to achieve a variety of buffer, to facilitate the implementation of dual simultaneous output. Filter circuit using bipolar secondary amplification filter, can not adjust the output level and the average waveform amplitude. Hardware shown in Figure 1.

2 shows the software flow chart and functions

Flow Chart Software 2.1

Software programming seeks to modular design, sub-main and several subroutines. Taking into account the implementation of more efficient assembly language, so all procedures are written in assembly language. Main program is responsible for receiving keyboard input control and its storage and display. Sine, square, ramp subroutine is mainly used for a variety of waveforms for a given frequency of small phase solver, come to the timer start value. Using timer interrupt control the output frequency and phase. Interrupt subroutine is mainly used to look-up table output of the voltage point. Output of the voltage waveform points. Various parts of the flow chart shown in Figure 2 (square wave and sine ramp flow and similar).

2.2 Function Presentation

Function shown in Figure 3 illustrates the situation.

3 Brief Introduction of

The intelligent dual digital signal source can produce a square wave, ramp, sinusoidal three kinds of signals. Each signal frequency range of 0.1 ~ 2 khz, the minimum scale 0.1 hz, the frequency by the digital display, clear and beautiful. Can simultaneously output the same frequency difference between two signals, one signal can be output.

Two outputs of the phase difference can be artificial, phase shift range of 0 ° ~ 360 °. All settings are done via the keyboard, and easy operation.

Output signal can be adjusted, the average between the -12 ~ +12 v, peak to peak at between 0 ~ 10 v, all adjustments are stepless adjustment. Full-featured, inexpensive, mass production cost of 80 yuan for laboratory and plant use, and good market prospects.

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RFID-based prepayment meter in the development

Source: International manufacturers

Author: Luo Xun Ding Qingsheng

Introduction

With the substantial increase in per capita electricity consumption, to promote a form of a system to use. The traditional mechanical meter accuracy is limited, will bring great error; when electricity consumption is large, the error will be difficult to accept. This article describes the electronic prepaid energy meter energy measurement IC is sampling of voltage and current signals are processed, and output active power is proportional to the frequency signal; microprocessor to calculate the pulse count by the amount of electricity. Users will rfid card (pre-purchase in the power sector, there is a fixed charge on the card in cash) near the meter, then mcu read the card by the amount of radio frequency chips will store it in eeprom, while this card is cleared. Meter will sound and the lcd display to remind the user recharge.

A hardware circuit design in general

By ad7755 energy measurement, and low power consumption, known for msp430 mcu interface, then ds1302 as a clock, the data stored in the 24lc16 eeprom. With the work of mfrc5 00 at 13.56 mhz chip to achieve the pre-paid card data read. Hardware block diagram shown in Figure 1.

1.1 metering features and interface module ad7755

ad7755 analog devices is produced by power measurement integrated circuits, technical indicators over the iec1036 specified accuracy requirements. It is worth mentioning that the existing domestic alternative, Shanghai Belling’s bl0932 can be a good alternative to ad7755. Here ad7755 work in this way: current and power through its transformer into the input channel. Rated voltage and current channels at the maximum output voltage to the design of semi-scale, so that the meter can meet the overvoltage and overcurrent requirements. Received the output frequency cf microcontroller port, set the scf = 0, s1 = 0, s0 = 1, cf the maximum output frequency of 21.76 hz, mcu input pulse count, the count is the size of which reflects the amount of power consumption . In this design, the shunt resistor 340 μω conditions, table for the 3200 constant pulse / kwh, per kwh electricity generated 3200 pulses. Cf The optocoupler output from the counter to the mcu.

1.2 mcu module msp430

msp430 mcu is ti’s ultra-low power 16-bit microcontroller; using reduced instruction set; has a wealth of on-chip peripherals, powerful, and has very low power consumption, especially for three table design. In this selection with a lcd driver and i / o rich msp430f435. msp430f435 80 and 100 in two packages (in this selection of 80 small packages). mcu as the circuit core module, to deal with the various peripherals, not only to count the ad7755 is responsible for the measurement of the output pulse value, but also to convert it to the amount and variety of external expansion interface chip to coordinate and handle.

1.3 Clock Module ds1302

Meter time to ensure the accuracy of the clock circuit is required. In this selection of dallas company announced high-performance, low power, real-time clock with a ram chip ds1302, can be years, months, weeks, days, hours, minutes, seconds for time, and has a leap year compensation, wide operating voltage 2.5 ~ 5.5 v. ds1302 using three-wire interface to communicate with the msp430 microcontroller. This part mainly for ds1302 serial clock signal and the analog and power-down protection circuit design.

1.4 external expansion memory module 24lc16

As a measuring instrument requires a lot of data (such as current and voltage coefficients, time billing form, accumulated billing table, etc.) change or modification by normal means, but not because of the interference and rewrite the system, not because of loss of power outages and other events. Serial eeprom is the current instrument design the most appropriate device. Here’s 24lc16 use microchip company to achieve this function. 24lc16 is a i2c interface eeprom. Its capacity is 2048 × 8-bit, 8 pages of 256 bytes. As msp430f435 without i2c interface, so this should be i2c bus simulation. The main difficulty or delay. LCD module and keyboard, and rs232 communication is relatively simple, each module is controlled by mcu.

2 rfid implementation process of pre-paid

rfid (radio frequency identification, radio frequency identification), is a non-contact automatic identification technology. It is through the RF signal automatic target recognition and access to relevant data, identify the work without human intervention, can work in harsh environments; operation quickly and conveniently. According to the different frequency bands, rfid system is divided into low and high frequency: low frequency system is mainly concentrated in the close-rfid 125 khz, 13.56 mhz band; high frequency long range rfid system is mainly concentrated in the frequency band (902 mhz ~ 928 mhz) 915 mhz, 2.45 ghz , 5.8 ghz.

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January 2012 Archive

Microcontroller-based circuit design of four BCD encoder 0

80C51 microcontroller C8051F020 and the similarities and differences

Microcontroller application in power supply design

AT89C51 in the application of wireless data transmission

Monitoring network design in the application of programmable

MCU read of CF card

AT88RF256 RF card reader design

LPC3180 ARM9 microcontroller hardware and software platform

Intelligent two-way digital signal

RFID-based prepayment meter in the development

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