The Design Of Test And Measurement Instruments’ USB Bridge Driver And Firmware

USB has many outstanding advantages, such as easy to use, support hot plug, efficient data transmission. Because of this, it has been widely used by users and manufacturers. In order to provide better support for test and measurement instrument, USB organization specially set the USBTMC protocol standard. USB has two major issues in terms of test and measurement. First, the signal transmitted by bus is not the local signal needed by the module of test instrument. Second, when assembling automatic measurement system, both control machine and instrument only support USB host interface. Neither of them can do inter communication by using USB host interface. Thus, USB needs to provide two connections. One is converting signal by change global bus to local bus. Another is USBSlave protocol switch, which implements the communication between control machine and instrument.Measurement instruments have two categories: for acquisition and for generation. For instruments like DVM, power meter etc, with fewer commands and data on bus the inter-communication would not be a problem. While for oscilloscope, spectrometer etc, there would be a huge amount of data transmitted on the bus, thus the USB bridge needs to provide one-time and BULK read-write data pipeline. This paper will, according to the requirement of the measurement instrument, explore and solve the two major issues mentioned above. The following is the structure of this paper:1. Research the general USB protocol.Based on the data transmission demand of measurement instrument, developing USB general driver solutions to windows and linux respectively. Device should be based on CY7C68013 A GPIF design pattern. CY7C68013 A host will be based on library libusb_win32 and linux_libusb.2. Study USBTMC protocol, according to the requirements of instrument, solves the 2nd issued. Firstly, analyze the requirements of the double USBSlave drive bridge and design the scheme which accords with USBTMC protocol. Then, on the basis of double USBSlave property requirement, select Vinculum II chip which have two USBSlave interfaces. Lastly, implement the USBTMC to FT232 bridge scheme.3. Complete USB driver programming. On the basis of the USB bridge scheme,USB bridge driver program respectively. CY7C68013 A firmware programming, Windows and linux host USB driver programming is for the first kind of bridge; VNC2 firmware programming is the main task of the USBTMC to FT232 bridge.4. Test the two kinds of USB bridge driver respectively to verify the function. Choosing the test method and test tools test driver design is correct.Test results show that the first kind of USB driver bridge can convert signal from USB global bus to local bus, the USBTMC to FT232 bridge can realize USBTMC protocol and FT232 serial protocol conversion, and support the communication between control machine and instrument through USB host port. They have application value. Windows USB bus convers to local bus driver bridge has been used in arbitrary waveform generator project, it works very well.