Outline of USB connector design
USB,Universal Serial Bus(Universal Serial Bus),was jointly developed by Compaq,IBM,Microsoft and other companies at the end of 1994.After six years of development,USB has now developed to version 2.0.The USB 2.0 protocol supports all existing USB devices,plugging USB 1.1 devices into the USB 1.1 PC interface and being electrically compatible with USB 1.1 connections.
1,USB bus characteristics:
(1)the data transmission rate is high.
(2)data transmission is available.
(3)hang multiple USB devices at the same time.
(4)USB interface can supply power for equipment.
(5)support hot swap.
USB also has some new features,such as real-time(which enables effective real-time communication with a device),dynamism(which enables dynamic switching between interfaces),Federation(which allows interfaces with different but similar characteristics to be federated),and versatility(which allows different interfaces to use different ones).Power supply mode).
2,the structure and typical application of USB interface:
The USB interface pin definition is shown in Figure 4.USB interface data transmission distance is not more than 5 meters.Its typical application is shown in Figure 5 below.
Data transmission methods on USB bus include controlled transmission,synchronous transmission,interrupt transmission and block data transmission.In the system shown in Figure 5,USB HOST adopts different data transmission characteristics according to the speed and usage characteristics of external USB devices.For example,the keyboard and mouse attributes are changed by controlling transmission,the keyboard and mouse are required to input data by interrupting transmission,and the display attributes are changed by controlling transmission.
USB2.0 device:Cypress FX2 series;
High speed ADC:TI,LT and AD's high speed(40MSPS to 80MSPS)8 bit ADC series;
High precision ADC:TI,LT,AD's medium speed(2MSPS to 40MSPS)12/14 bit ADC series;
High speed DAC:AD,LT's high-speed(40MSPS to 80MSPS)8 bit DAC series;
High precision DAC:AD,LT medium speed(20MSPS to 80MSPS)12/14 bit DAC series;
4,the main features of EX-USB FX2:
The EZ-USB FX2 chip includes an 8051 processor,a serial interface engine(SIE),a USB transceiver,8.5KB on-chip RAM,4KB FIFO memory,and a general programmable interface(GPIF),as shown in Figure 2.FX2 is a fully integrated solution that takes up less board space and shortens development time.
EZ-USB FX2 has 1 unique architectures,including 1 intelligent serial interface engines(SIE).It performs all the basic USB functions,frees the embedded MCU for dedicated functions,and guarantees its continuous high-performance transmission rate.FX2 also includes two general purpose programmable interfaces(GPIFs),allowing it to be"glueless"to connect to any ASIC or DSP,and it supports all general bus standards,including ATA,UTOPIA,EPP,and PCMCIA.EZ-USB FX2 is fully applicable to USB2.0 and is compatible with USB1.1 downwards.
FX2 has 3 forms of encapsulation:56 pin SOPP,100 pin TQFF(thin square flat package),and 128 foot TQFP.The difference between pins is the difference between the number of input and output pins in order to meet different application requirements.
5.The functions of this system:
1.PGA(Programmable Gain Amplifier),ADC using 20MSP-40MSPS medium-high speed 8-bit ADC,DAC using 20MSPS-40MSPS medium-high speed 8-bit DAC.
2,SRAM adopts 128K*8 high speed SRAM.
3,3,with 16 channels digital input and 16 channels digital output,can also be configured as 32 channels digital output or 32 channels digital input.
4,the introduction document of USB2.0 device is compiled to familiarise users with various features of Cypress USB devices.
5,according to various internal characteristics of USB2.0 devices,the corresponding firmware code and upper layer test program are compiled.
6.The internal transmission speed test program of USB2.0 is compiled,taking the multimedia image display program as an example(download the image to FX2,read it back to the host and calculate the number of display frames per second).
7,the Slave FIFO of USB2.0 is extracted,and users can connect Slave FIFO channel to user board to test.
8.Analog data acquisition and display software can be used as digital storage oscilloscope with complete functions.
USB2.0 development system is a general data acquisition and analysis system.It can be used as a high-performance portable(mainly for mobile systems)data acquisition card.It can also be used as a high-performance evaluation board for ADC and DAC devices.It can also be used as a high-performance portable virtual instrument.Because of the USB2.0 interface,it can be used.Enough to overcome the weakness of the portable virtual instrument which used parallel port or USB1.1 interface in the past.