WP369可擴展式處理平臺-各種嵌入式系統的理想解決方案 ：Delivering unrivaled levels of system performance,flexibility, scalability, and integration to developers,Xilinx's architecture for a new Extensible Processing Platform is optimized for system power, cost, and size. Based on ARM's dual-core Cortex™-A9 MPCore processors and Xilinx’s 28 nm programmable logic,the Extensible Processing Platform takes a processor-centric approach by defining a comprehensive processor system implemented with standard design methods. This approach provides Software Developers a familiar programming environment within an optimized, full featured,powerful, yet Low-cost, Low-power processing platform.
上傳時間： 2013-10-18
上傳用戶：cursor
波長信號的解調是實現光纖光柵傳感網絡的關鍵，基于現有的光纖光柵傳感器解調方法，提出一種基于FPGA的雙匹配光纖光柵解調方法，此系統是一種高速率、高精度、低成本的解調系統，并且通過引入雙匹配光柵有效地克服了雙值問題同時擴大了檢測范圍。分析了光纖光柵的測溫原理并給出了該方案軟硬件設計，綜合考慮系統的解調精度和FPGA的處理速度給出了基于拉格朗日的曲線擬合算法。 Abstract: Sensor is one of the most important application of the fiber grating. Wavelength signal demodulating is the key techniques to carry out fiber grating sensing network， based on several existing methods of fiber grating sensor demodulation inadequate， a two-match fiber grating demodulation method was presented. This system is a high-speed， high precision， Low-cost demodulation system. And by introducing a two-match grating effectively overcomes the problem of double value while expands the scope of testing. This paper analyzes the principle of fiber Bragg grating temperature and gives the software and hardware design of the program. Considering the system of demodulation accuracy and processing speed of FPGA，this paper gives the curve fitting algorithm based on Lagrange.
上傳時間： 2013-10-10
上傳用戶：zxc23456789
Abstract: Many modern industrial, medical, and commercial applications require temperature measurements in the extended temperature rangewith accuracies of ±0.3°C or better, performed with reasonable cost and often with Low power consumption. This article explains how platinumresistance temperature detectors (PRTDs) can perform measurements over wide temperature ranges of -200°C to +850°C, with absolute accuracyand repeatability better than ±0.3°C, when used with modern processors capable of resolving nonlinear mathematical equation quickly and costeffectively. This article is the second installment of a series on PRTDs. For the first installment, please read application note 4875, "High-Accuracy Temperature Measurements Call for Platinum Resistance Temperature Detectors (PRTDs) and Precision Delta-Sigma ADCs."
上傳時間： 2013-11-06
上傳用戶：WMC_geophy
Delta-sigma ADCs, with their high accuracy and high noiseimmunity, are ideal for directly measuring many typesof sensors. Nevertheless, input sampling currents canoverwhelm high source impedances or Low-bandwidth,micropower signal conditioning circuits. The LTC®2484family of delta sigma converters solves this problem bybalancing the input currents, thussimplifying or eliminatingthe need for signal conditioning circuits.
上傳時間： 2015-01-03
上傳用戶：潛水的三貢
Accurate measurement of the third order intercept pointfor Low distortion IC products such as the LT5514 requirescertain precautions to be observed in the test setup andtesting procedure. The LT5514 linearity performance ishigh enough to push the test equipment and test set-up totheir limits. A method for accurate measurement of thirdorder intermodulation products, IM3, with standard testequipment is outlined beLow.It is also important to correctly interpret the LT5514specification with respect to ROUT, and the impact ofdemo-board transmission-line termination loss whenevaluating the linearity performance, as explained in theLT5514 Datasheet and in Note 1 of this document.
上傳時間： 2013-11-14
上傳用戶：l254587896
Frequently, voltage reference stability and noise defi nemeasurement limits in instrumentation systems. In particular,reference noise often sets stable resolution limits.Reference voltages have decreased with the continuingdrop in system power supply voltages, making referencenoise increasingly important. The compressed signalprocessing range mandates a commensurate reductionin reference noise to maintain resolution. Noise ultimatelytranslates into quantization uncertainty in A to D converters,introducing jitter in applications such as scales, inertialnavigation systems, infrared thermography, DVMs andmedical imaging apparatus. A new Low voltage reference,the LTC6655, has only 0.3ppm (775nV) noise at 2.5VOUT.Figure 1 lists salient specifi cations in tabular form. Accuracyand temperature coeffi cient are characteristic ofhigh grade, Low voltage references. 0.1Hz to 10Hz noise,particularly noteworthy, is unequalled by any Low voltageelectronic reference.
上傳時間： 2013-10-30
上傳用戶：wxhwjf
基于通用集成運算放大器，利用MASON公式設計了一個多功能二階通用濾波器，能同時或分別實現低通、高通和帶通濾波，也能設計成一個正交振蕩器。電路的極點頻率和品質因數能夠獨立、精確地調節。電路使用4個集成運放、2個電容和11個電阻，所有集成運放的反相端虛地。利用計算機仿真電路的通用濾波功能、極點頻率和品質因數的獨立控制和正交正弦振蕩，從而證明該濾波器正確有效。 Abstract: A new multifunctional second-order filter based on OPs was presented by MASON formula. Functions， such as high-pass， band-pass， Low-pass filtering， can be realized respectively and simultaneously， and can become a quadrature oscillator by modifying resistance ratio. Its pole angular frequency and quality factor can be tuned accurately and independently. The circuit presented contains four OPs， two capacitors， and eleven resistances， and inverting input of all OPs is virtual ground. Its general filtering， the independent control of pole frequency and quality factor and quadrature sinusoidal oscillation were simulated by computer， and the result shows that the presented circuit is valid and effective.
上傳時間： 2013-10-09
上傳用戶：13788529953
SL811開發資料_包含源程序_電路圖_芯片資料:SL811HS Embedded USB Host/Slave Controller.The SL811HS is an Embedded USB Host/Slave Controller capable of communicate with either full-speed or Low-speed USB peripherals. The SL811HS can interface to devices such as microprocessors, microcontrollers, DSPs, or directly to a variety of buses such as ISA, PCMCIA, and others. The SL811HS USB Host Controller conforms to USB Specification 1.1.The SL811HS USB Host/Slave Controller incorporates USB Serial Interface functionality along with internal full-/Low-speed transceivers.The SL811HS supports and operates in USB full-speed mode at 12 Mbps, or at Low-speed 1.5-Mbps mode.The SL811HS data port and microprocessor interface provide an 8-bit data path I/O or DMA bidirectional, with interrupt support to alLow easy interface to standard microprocessors or microcontrollers such as Motorola or Intel CPUs and many others. Internally,the SL811HS contains a 256-byte RAM data buffer which is used for control registers and data buffer.The available package types offered are a 28-pin PLCC (SL811HS) and a 48-pin TQFP package (SL811HST-AC). Both packages operate at 3.3 VDC. The I/O interface logic is 5V-tolerant.
上傳時間： 2013-12-22
上傳用戶：a82531317
超聲波傳感器適用于對大幅的平面進行靜止測距。普通的超聲波傳感器測距范圍大概是 2cm~450cm，分辨率3mm（淘寶賣家說的，筆者測試環境沒那么好，個人實測比較穩定的 距離10cm~2m 左右，超過此距離就經常有偶然不準確的情況發生了，當然不排除筆者技術 問題。） 測試對象是淘寶上面最便宜的SRF-04 超聲波傳感器，有四個腳：5v 電源腳（Vcc），觸發控制端（Trig），接收端（Echo），地端（GND） 附:SRF 系列超聲波傳感器參數比較 模塊工作原理： 采用IO 觸發測距，給至少10us 的高電平信號； 模塊自動發送8個40KHz 的方波，自動檢測是否有信號返回； 有信號返回，通過IO 輸出一高電平，高電平持續的時間就是超聲波從發射到返回的時間．測試距離=(高電平時間*聲速(340m/s))/2; 電路連接方法 Arduino 程序例子： constintTrigPin = 2; constintEchoPin = 3; floatcm; voidsetup() { Serial.begin(9600); pinMode(TrigPin, OUTPUT); pinMode(EchoPin, INPUT); } voidloop() { digitalWrite(TrigPin, Low); //低高低電平發一個短時間脈沖去TrigPin delayMicroseconds(2); digitalWrite(TrigPin, HIGH); delayMicroseconds(10); digitalWrite(TrigPin, Low); cm = pulseIn(EchoPin, HIGH) / 58.0; //將回波時間換算成cm cm = (int(cm * 100.0)) / 100.0; //保留兩位小數 Serial.print(cm); Serial.print("cm"); Serial.println(); delay(1000); }
上傳時間： 2013-11-01
上傳用戶：xiaoyuer
注:1.這篇文章斷斷續續寫了很久,畫圖技術也不精,難免錯漏,大家湊合看.有問題可以留言. 2.論壇排版把我的代碼縮進全弄沒了,大家將代碼粘貼到arduino編譯器,然后按ctrl+T重新格式化代碼格式即可看的舒服. 一、什么是PWM PWM 即Pulse Wavelength Modulation 脈寬調制波，通過調整輸出信號占空比，從而達到改 變輸出平均電壓的目的。相信Arduino 的PWM 大家都不陌生，在Arduino Duemilanove 2009 中，有6 個8 位精度PWM 引腳，分別是3, 5, 6, 9, 10, 11 腳。我們可以使用analogWrite()控 制PWM 腳輸出頻率大概在500Hz 的左右的PWM 調制波。分辨率8 位即2 的8 次方等于 256 級精度。但是有時候我們會覺得6 個PWM 引腳不夠用。比如我們做一個10 路燈調光， 就需要有10 個PWM 腳。Arduino Duemilanove 2009 有13 個數字輸出腳，如果它們都可以 PWM 的話，就能滿足條件了。于是本文介紹用軟件模擬PWM。 二、Arduino 軟件模擬PWM Arduino PWM 調壓原理：PWM 有好幾種方法。而Arduino 因為電源和實現難度限制，一般 使用周期恒定，占空比變化的單極性PWM。 通過調整一個周期里面輸出腳高/低電平的時間比（即是占空比）去獲得給一個用電器不同 的平均功率。 如圖所示，假設PWM 波形周期1ms（即1kHz），分辨率1000 級。那么需要一個信號時間 精度1ms/1000=1us 的信號源，即1MHz。所以說，PWM 的實現難點在于需要使用很高頻的 信號源，才能獲得快速與高精度。下面先由一個簡單的PWM 程序開始： const int PWMPin = 13; int bright = 0; void setup() { pinMode(PWMPin, OUTPUT); } void loop() { if((bright++) == 255) bright = 0; for(int i = 0; i < 255; i++) { if(i < bright) { digitalWrite(PWMPin, HIGH); delayMicroseconds(30); } else { digitalWrite(PWMPin, Low); delayMicroseconds(30); } } } 這是一個軟件PWM 控制Arduino D13 引腳的例子。只需要一塊Arduino 即可測試此代碼。 程序解析：由for 循環可以看出，完成一個PWM 周期，共循環255 次。 假設bright=100 時候，在第0~100 次循環中，i 等于1 到99 均小于bright，于是輸出PWMPin 高電平； 然后第100 到255 次循環里面，i 等于100~255 大于bright，于是輸出PWMPin 低電平。無 論輸出高低電平都保持30us。 那么說，如果bright=100 的話，就有100 次循環是高電平，155 次循環是低電平。 如果忽略指令執行時間的話，這次的PWM 波形占空比為100/255，如果調整bright 的值， 就能改變接在D13 的LED 的亮度。 這里設置了每次for 循環之后，將bright 加一，并且當bright 加到255 時歸0。所以，我們 看到的最終效果就是LED 慢慢變亮，到頂之后然后突然暗回去重新變亮。 這是最基本的PWM 方法，也應該是大家想的比較多的想法。 然后介紹一個簡單一點的。思維風格完全不同。不過對于驅動一個LED 來說，效果與上面 的程序一樣。 const int PWMPin = 13; int bright = 0; void setup() { pinMode(PWMPin, OUTPUT); } void loop() { digitalWrite(PWMPin, HIGH); delayMicroseconds(bright*30); digitalWrite(PWMPin, Low); delayMicroseconds((255 - bright)*30); if((bright++) == 255) bright = 0; } 可以看出，這段代碼少了一個For 循環。它先輸出一個高電平，然后維持(bright*30)us。然 后輸出一個低電平，維持時間((255-bright)*30)us。這樣兩次高低就能完成一個PWM 周期。 分辨率也是255。 三、多引腳PWM Arduino 本身已有PWM 引腳并且運行起來不占CPU 時間，所以軟件模擬一個引腳的PWM 完全沒有實用意義。我們軟件模擬的價值在于：他能將任意的數字IO 口變成PWM 引腳。 當一片Arduino 要同時控制多個PWM，并且沒有其他重任務的時候，就要用軟件PWM 了。 多引腳PWM 有一種下面的方式： int brights[14] = {0}; //定義14個引腳的初始亮度，可以隨意設置 int StartPWMPin = 0, EndPWMPin = 13; //設置D0~D13為PWM 引腳 int PWMResolution = 255; //設置PWM 占空比分辨率 void setup() { //定義所有IO 端輸出 for(int i = StartPWMPin; i <= EndPWMPin; i++) { pinMode(i, OUTPUT); //隨便定義個初始亮度,便于觀察 brights[ i ] = random(0, 255); } } void loop() { //這for 循環是為14盞燈做漸亮的。每次Arduino loop()循環， //brights 自增一次。直到brights=255時候，將brights 置零重新計數。 for(int i = StartPWMPin; i <= EndPWMPin; i++) { if((brights[i]++) == PWMResolution) brights[i] = 0; } for(int i = 0; i <= PWMResolution; i++) //i 是計數一個PWM 周期 { for(int j = StartPWMPin; j <= EndPWMPin; j++) //每個PWM 周期均遍歷所有引腳 { if(i < brights[j])\ 所以我們要更改PWM 周期的話，我們將精度（代碼里面的變量：PWMResolution）降低就行，比如一般調整LED 亮度的話，我們用64 級精度就行。這樣速度就是2x32x64=4ms。就不會閃了。
上傳時間： 2013-10-23
上傳用戶：mqien
