| Intraocular pressure measurement based on interferential laser uses way ofnon-contact, thus can reduce pain and infection. In the same time, the device has theadvantages of high precision, simple configuration, low cost and easy forpopularization.This paper introduces the data acquisition system in the measurement whichdeals with the electronic signals after O/E transform. USB interface technology isused successfully in the system. The traditional data acquisition system is made intothe form of board and connected to the computer through Serial port, Parallel port,ISA or PCI interface, which is inconvenient to use and limited by resources of thecomputer. In this paper, a novel interface – USB is introduced, which is more andmore favored by people due to its supporting of plug and play, easy to use, high speedand compatibility. In the system, data acquired by the MCU is transferred to the PC tobe dealt with through USB cable. It contains of A/D conversion unit, USB interfaceunit, Keys & LCD display unit, stepping motor driving unit. TLC2543 ADC changesthe analog signals to digital ones and then send them to the MCU, USB interfacecircuit PDIUSBD12 changes the data to the format of USB and then transfers them tothe PC. Keys & LCD units are used to improve interaction between machine andoperators, not only to reflect status of the running system, but also to implementappropriate interference on certain conditions;Driving circuits are used to drive thestepping motor of 57BYG613. Up to now, schematic design, PCB design, USBfirmware, driving program of LCD and motor driving have been completed. TheMCU used is AT89C52. Circuit design software adopts Protel99 SE and software isdeveloped under the environment of KEIL C. The system has the advantage of simpleconfiguration, high precision, easy to use and friendly interface.The system also has the adaptability to deal with signals of temperature,displacement, etc., when the corresponding sensors are added. |
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