单片机毕设论文文献翻译数据采集

单片机毕设论文文献翻译数据采集内容摘要：

pins are configured as inputs, the noise faithfully masquerades as intermittent data. Fortunately, however, a simple software AND function filters out the induced noise and they say digital filtering is tough! As an alternative, you can configure the unused ports as outputs. The above code works perfectly, but establishing correct circuit performance can prove difficult. The interrupt pulse from the 181。 C es and goes so fast (in 1181。 s) that only a storage oscilloscope can detect it. If a suitable oscilloscope is not available, you can insert a delay routine immediately after the CONVST line has been set HIGH to enable a more leisurely viewing of the interrupt signal. The PC Interface The key ponent interfacing the microprocessor to the PC is the serially addressed UART (MAX3100). It takes input from the microprocessor via its 4wire SPI/Microwire bus3, and converts this data to the format used by most RS232 patible devices. An industrystandard, micropower 2TX/2RX transceiver (MAX202E) implements the level translation. This UART, which has hardware and software shutdown modes and es in a tiny QSOP package, is ideally suited for lowpower portable appliances. For hazardous environments, its interface also allows IrDA munication by attachment of suitable optical devices. Other features (not required in this application) include a receive buffer and an interrupt flag to give status information on the transmit and receive registers. A softwarebased SPI routine is implemented for exporting the code to microprocessors lacking a builtin SPI bus. The code shows that this is a trivial task, and ments guide the uninitiated through the clock cycles of the SPI bus. If a dedicated SPI port is used, it is worth noting that the MAX310039。 s serial clock line (SCLK) must start in the LOW state when CS is asserted. If this requirement presents a problem, you should cycle the SCLK line before entering the SPI routine. Note the time required for RS232 data to transmit. At 9600 baud, it takes more than one millisecond to transmit eight bits of data together with the start and stop bits. This is obvious in hindsight, but it can give the designer hours of undeserved enjoyment not only in wondering why data is not reaching the PC correctly, but also in illustrating the difference in operating speeds of the microprocessor and the RS232 link. A simple 10ms delay inserted in the code allows data transmission and processing at the PC end. Note also that the RS232 spec does not detail the signal protocol (start and stop bits, etc.)。 just the voltage levels, slew rate, and connector details. The MAX3100 and MAX202E, however, handle all the standards for making data pliant with RS232, and in a protocol expected by the PC. The Windows Interface The Windows program was written in Visual Basic Version 6. It takes readings from the RS232 port using the MSComm function, configured to accept text, and converts this data to ASCII. It also translates each 16bit data block back to the voltage and current measurements obtained from analogsensing circuitry that precedes the ADC input. From these results, the input power, output power, and efficiency are calculated and displayed on the PC screen, rounded to three decimal places. In addition, the system can freeze the results if they need to be logged. The measured efficiency figures were far from consistent. This was accounted for by noticing ripple on the current and voltage waveforms. The resistors were bypassed with 10nF capacitors to reduce the currentripple readings, but the resistivedivider works measuring voltage were left unbypassed. Thus, the measured ripple (20mV on the input and 100mV on the output) accounted for the 177。 3% vari ation in efficiency measurements. As results are read into the PC, missing data produces incorrect readings on the PC screen. The time intervals between arriving packets of data were therefore measured. If any interval exceeded seconds, the PC counter was reset in anticipation of the first character in the subsequent data packet. Results The device under test (DUT) was the MAX1705, a boost DCDC converter configured in PWM mode. Loads were applied to the evaluation kit, and the results taken by freezing the MAX125 PC program and reading values from the screen. The results were then confirmed using the (now obsolete) digital multimeter, and pared with the expected efficiency as given by graphs in the datasheet: Table 1. Load/ Vin/V Iin/A Vout/V Iout/A Efficiency/% (exp. Eff/%) 95 50 92 100 83 390 56 Calibration, Errors and Tweaks Though digital purists may argue differently, the analog board layout must be impeccable to obtain the best circuit performance. All power rails to the analog ICs should be thick, and decoupled to ground with capacitors physically close to the devices: at least 1uF (tantalum) in parallel with 100nF (ceramic). A good ground plane should be included, especially around the MAX471, because high frequency, high amplitude currents occupy that territory. The resistors on the MAX471 should b。