Research And Implementation Of The TMC Instrument Control Based On USB Interrupt Pipe

USB has been applied in many TMC(Test and Measurement Class)instruments widely due to its advantages,such as convenient to use,hot plug,unified standard,and so on.With the development of electronic technology,the computer has become the controller of the TMC instruments.However,the computer only provides the USB Host interfaces,which can't connect with USB Host interfaces providing by another computer directly using USB cable.The main task of this thesis is research and implementation of USBTMC bus bridge,which is used to realize the communication between control PC and instrument PC through their USB Host interfaces in USB cable.This USBTMC bus bridge supports the USB protocol and the USBTMC protocol in order to improve the using compatibility in control PC.According to the demands of testing instruments,main researches contents of USBTMC bus bridge are as follows:1.To design the overall scheme of the USBTMC bus bridge.The requirements analysis of the USBTMC bus bridge is accomplished according to the generic USB protocol and the USBTMC protocol,also including the demand in data transfer of TMC instruments.Due to the requirements analysis,The overall scheme of the USBTMC bus bridge is designed by two pieces of CY7C68013 A USB chip in "back to back" connection.2.Completing the firmware design of USBTMC bus bridge.The firmware design is composed of designing the description file,realizing the USBTMC class request and designing data transfer.The inportant point of USBTMC class request is the handshake interaction between two USB chips using I/O pins.The design of data transfer includes interrupt transfer,bulk transfer,also includes GPIF mode and Slave FIFO mode on USB chips.The USB interrupt transfer is designed to solve the communication barrier between two USB Host interfaces,and the bulk transfer is adhered to the special transfer format in USBTMC protol.3.Designing the USB device drivers of the bus bridge.USB device drivers should include the control PC and the instrument PC.In control PC,the USB device driver is based on VISA which provides by NI,so that the application can call APIs of VISA to operate the USBTMC bus bridge directly.Another,cyusb.sys which provides by Cypress,is used in instrument PC.The application of instrument PC directly calls APIs of InstrUSBInterface.dll,which is secdently designed and packaged using CyAPI.lib.4.Testing and verifying the functions of USBTMC bus bridge.The test and verification of functions is divided into the closed loop and the on-line test.The closed loop test is to guarantee the distinguishing of the bus bridge in PC,the correctness of data transfer,the stability of data transfer,the speed of data transfer,USBTMC class request,and so on.And the on-line is to test the application of the bus bridge in instruments.The USBTMC bus bridge which this thesis designs has been tested and verified.The test results show that the bus bridge can realize data transmission,which has excess of 12 MBps speed in write or read.The bus bridge also realizes other demands.So the USBTMC bus bridge has the value of application in the field of test and measurement.