Development Of High Gain Multi-channels Data Acquisition Device With USB Interface

In this thesis, the up-to-date development of domestic and overseas data acquisition device is firstly described in detail. At present, data acquisition device with USB interface is expensive and in small amounts, and the amount of high gain data acquisition device with USB interface is even smaller. Based on that, a plan is constructively suggested for designing a data acquisition device, which should be in a lower price, and has programmable gains ranging from 0.5 to 128 and is multifunctional, and can be plugged and played conveniently. The project is discussed here in detail.The instrument adopts C8051F000 of Cygnal Co. as MCU, which integrates a 12-bit 100kspsADC,Watchdog Timer, programmable gain, 128B nonvolatile RAM and JTAG interface and whose abundant on-chip resource makes the design of the hardware circuit of the instrument simplified. The instrument uses USB bus power supply, which predigests the design of the power supply circuit, makes the design of the pocket instrument come true. The instrument communicates with computer through USB interface, so it has the function of plug and play, and can be used conveniently. The instrument uses chip PDIUSBD12 of PHILIPS Co. as USB interface chip, which conforms to the USB 1.1 protocol, and integrates 320B FIFO memory, analog transceiver, Philips Serial Interface Engine etc. .The transmission rate of 1MB/s between the instrument and computer can be realized by bulk mode or isochronous mode. The Philips Serial Interface Engine implements the full USB protocol layer including parallel/serial conversion, bit stuffing/de-stuffing, CRC checking/generation, address recognition, and handshake evaluation/generation etc.. The USB protocol and the realization of the USB communication are discussed in detail in this thesis. The instrument has eight analog input channels. There are 0.5, 1, 2, 4, 8, 16, 32, 64, 128 nine selectable gains provided at the input end of every channel in the instrument. According to the gains, the acquisition voltage range of every channel can be set from±15mV to±3.3V. The computer software is developed with VB6.0.The parameter setting of data acquisition is finished by computer, and computer can also be used to read the parameter of the instrument at any moment. Real-time data collected by the instrument are transmitted to computer and then are displayed. In this thesis, author expatiates the lay outing of function, the hardware design, the realization of USB communication and the software design etc. of the instrument. In the end, the whole thesis is summarized.