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AD7705 applies mediumly in electronic balance
From;    Author:Stand originally

1 foreword

Country requirement of level of 3 grade level: The very precision that weighs heavy data and clog is less than 1/1000 - 1/5000, accordingly, what data outputs after classics AD is changed is effective should be in 13 above. AD company rolls out by bumper and gain but process designing amplifier (PGA) , Σ - Δ adjuster, but the tiny signal that 16 AD7705/06 of the composition such as filter of process designing number can detect sensor directly undertakes A/D is changed, its have high resolution, wide dynamic range, from calibration, admirable fight depress of noise function and low report the characteristic such as power comsumption, agree with the need that calls next personal computer signal in heavy system processing. In the design, we decide the corresponding parameter of AD7705 takes:

Output data replaces rate: 50Hz; system gain: 64; efficient resolution: 15.

2 hardware are designed

Should satisfy in front affirmatory AD7705 parameter, of the AD7705 in the design advocate clock takes: FCLK =2.4576MHz.

The serial data interface of AD7705 includes 5: Piece choose input mouth, serial Schmidt logic inputs clock SCLK, data inputs buccal DIN, changeover data outputs buccal DOUT, the condition signal that indicates data in train outputs a mouth. When should be low n among them, changeover data is readable take; to cannot be read otherwise take.

Can come true by AT89C51 pitch on in the design, also but ground connection; designs lieutenant general ground connection originally.

SCLK has two kinds of basic wiring kind: The pin that did not use in the P2 mouth that ① SCLK receives AT89C51 (receive P2.2 for instance) , the data input, another pin that in outputting upright DIN, DOUT to receive P2 mouth together, did not use (for instance: P2.3) . In this kinds join means falls, the communication sequential that can use AD7705 of imitate of manual process designing only is opposite with coming true the operation of AD7705. ② SCLK receives the synchronous pulse of AT89C51 to output upright TXD, the serial number that the data input of AD7705, output carries DIN, DOUT to receive AT89C51 together carries RXD according to input, output. In this kinds join means falls, of the data to AD7705 read take can press 51 series sheet piece machine is serial working way of the mouth 0 finish, also can read mediumly by ① write means to finish. The means wiring that in ② is being pressed in this design, introduces. Can accept the pin that did not use in mouth of common P1, P2, inquire through the program whether this pin is low n, of data of the register in realizing pair of AD7705 thereby read take. What also can receive AT89C51 is exterior interrupt 1 or interrupt 0 pin, pass what break pattern or interrupt data of the register in inquiring means realizes pair of AD7705 to read take. Receive in this design exterior interrupt 1 pin.

Net of beautiful labour Electromechanical
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