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Universal Serial Bus and Its Application in Virtual Instrument


Program does not communicate directly with the hardware, but rather to create and send a URB request block in the form of the command to the Windows operating system provided by the USB bus driver, the bus to complete the direct interaction with the hardware. The second is the equipment side of the microcontroller programming. Mainly to complete USB protocol processing and data exchange and device applications; The third is PC-side data processing programming. Mainly completes data reception, processing, and accordingly the results based on the expression or action. On the basis of USB interface, a USB device developed a virtual angular displacement measuring instrument, the instrument hardware from the USB controller, 89C52 single-chip microprocessor and composed of functional circuit, the circuit shown in Figure 1. Figure I PDIUSBD12 chip using this instrument (Figure 1, U1) as a USB controller. The devices can be connected with a variety of commonly used microprocessors, development time is short, low risk, low cost, high performance and low cost is a USB device. PDIUSBD12 the ALE pin connection is low, indicating a single address / data bus configuration. The data port is connected with the microprocessor port P0 to form an 8-bit parallel data bus. 6MHz crystal oscillator using low-cost controller with integrated on-chip PLL generates the clock signal clock. Microprocessor clock signal provided by the PDIUSBD12 the CLKOUT pin. USB connection leads directly from the PDIUSBD12. PDIUSBD12 chip integration of the 1.5k1) pull-up resistor, default is not connected with Vce. Establish the connection to send commands through the microprocessor to achieve, which makes the microprocessor and the USB connection in the initialization can be done before. A0 feet to receive the microprocessor address bits sent, if it is a select command instruction, if it is 0, select the data. INT-N is an interrupt instruction signal,[link widoczny dla zalogowanych], active low, used to notify the microprocessor data transfer is complete. Because the signal is open drain output, so the pull-up resistor to be used. ・ 16.89 C52 single-chip microprocessor (Figure 1, u2) on the one hand as PDIUSBD12 the controller, the host of devices to receive and respond to the orders. Equipment is not connected with the host before, 89C52 on PDIUSBD12 initialize,[link widoczny dla zalogowanych], set the internal clock, select the internal connections, set the operating mode and the receiving host assigned address and enable the USB interface, the host and device, \. After the device and host connectivity, 89C52 and the host response style communication between the complete device descriptor, configuration descriptor transmission. On the other hand, 89C52 also doubles as a data collection instrument and processor. Measurements provided by the functional circuit signals were sent to counter TO and T1, a single count of interrupt. In the interrupt service routine, the value of P1.0 to by the internal counter unit plus 1 or minus 1. Instrument function of a circuit U3,[link widoczny dla zalogowanych], respectively, by the chip U7 and external pull-up resistor composition. Angular displacement measuring sensor is an incremental encoder, the phase difference of 90 degrees to the two output signals are connected persons A, B two points. Signal through the inverse, reconstructive surgery, but also produced a two sensor output signals and inverting the signal. Signal by the different U6 or after the two opposite phase to obtain second harmonic signals. By sharing the interrupt, can measure the signal to achieve the fourth harmonic. D flip-flop (U7) is used to determine the steering encoders. Device driver designed to reference [5], device-side SCM program is designed to reference [1], will not go. IV Conclusion This article follows the USB1.1 specification, developed the virtual angular displacement measuring instruments USB interface. Implement plug and play the instrument with a simple hardware structure, high speed, stable, etc., can be easily connected to the computer. Proved, USB virtual instrument can be used as practical interface, through the expansion of the hub,[link widoczny dla zalogowanych], but also for higher integration of virtual instruments. References [1] CHEN Yi such as translation. USB Daquan. Beijing: China Electric Power Press, 2001 [2] Zhang Nian Huai and so on. USB Bus Interface Developer Guide. Beijing: National Defence Industry Press, 20ol [3] Wang province books. Universal Serial Bus and its application. Application Research of Computers, 2000 (1) [4] Xu Ning and so on. CCD linear array access universal serial bus acquisition FI design. Optical technology. 2002 (5) [5] Sun Yi such as translation. WindowsWDM Device Driver Development Guide. Beijing: Mechanical Industry Press,[link widoczny dla zalogowanych], 2000T ... - Sweet T ore l | r good at learning ● l l_r buildings Ding

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