“USB3.0 high-speed data acquisition system, with its superior performance such as 5Gbps bandwidth and plug-and-play, has been paid more and more attention by people. At present, the commonly used USB3.0 communication chips mainly come from the EZ USB FX3 series chips developed by the US Cypress (CYPRESS) company and the uPD720200 series chips developed by the Japanese NEC company. Both of them not only have the advantages of high integration, powerful functions, and compatibility with USB2.0, but also both manufacturers provide powerful development toolkits, which can greatly shorten the development cycle and are deeply loved by developers.
USB3.0 high-speed data acquisition system, with its superior performance such as 5Gbps bandwidth and plug-and-play, has been paid more and more attention by people. At present, the commonly used USB3.0 communication chips mainly come from the EZ USB FX3 series chips developed by the US Cypress (CYPRESS) company and the uPD720200 series chips developed by the Japanese NEC company. Both of them not only have the advantages of high integration, powerful functions, and compatibility with USB2.0, but also both manufacturers provide powerful development toolkits, which can greatly shorten the development cycle and are deeply loved by developers. At present, some acquisition systems use traditional 51 series single-chip microcomputers as the main control chip, which cannot give full play to the bandwidth of USB3.0 and have poor performance. Although the CPLD chip can work at a high frequency, it is not as flexible and easy to use as the single-chip microcomputer. Therefore, this paper adopts the latest high-speed ADS7886 chip of TI company as the A/D conversion chip, the latest MSP430 single-chip microcomputer as the main control chip, and NEC company’s UPD720200 as the A/D conversion chip. USB3.0 communication chip, research and design a set of temperature data acquisition system based on USB3.0 bus. After testing, the system can realize high-speed temperature data acquisition.
1 System hardware design
The overall framework of the system is shown in Figure 1. After the signal collected by the temperature sensor is converted into a digital signal by the A/D conversion chip ADS7886, it is sent to the main control chip MSP430, and then sent to the USB3.0 host interface chip uPD720200 after processing. Finally, the data is sent to the USB host at a speed of 5Gbps. .
1.1 A/D module
This module uses the latest high-speed A/D sampling chip ADS7886 from TI Company in the United States. ADS7886 is a 12-bit serial high-speed precision A/D chip. In order to improve the accuracy of the system, we designed and adopted the REF3030 chip to provide a 3V reference voltage. A The 3rd pin of DS7886 is the analog signal input port, the 4th pin is the 1MHz working clock signal input port, the 6th pin is the chip select signal terminal, and the 5th pin is the output terminal after the analog signal is converted into a digital signal for the MSP430 MCU read.
1. 2 MSP430 minimum system module
The minimum system of MSP430 is shown in Figure 3, which is mainly composed of MSP430 microcontroller, crystal oscillator circuit and power supply. Among them, P1.4 is the serial data input terminal of ADC7886, P2.0~P2.3 are used to connect the USB3.0 communication chip uPD720200, and P1.6 and P1.7 are connected to two LED indicators to Display the current working status .
1.3 USB transmission module
The module is shown in Figure 4. We selected uPD720200 from NEC Company as the USB3.0 communication chip, which completely complies with the USB3.0 communication protocol and interface specification. The pins U3TXDP1, U3TXDN1, U3RXDP1, U3 RXDN1 of uPD720200 are respectively connected with pins P2.0~P2.3 of MSP430.
Its working principle is as follows: when collecting data, after uPD720200 receives the user’s data collection request, it will form a corresponding control signal and transmit it to MSP430 through P2.2 and P2.3; MSP430 will then send a control signal to ADS7886 to collect data, And upload the data collected by ADS7886 to uPD720200 through P2.0 and P2.1; the SIE (serial interface engine) of uPD720200 sends the data into the designated receiving buffer for the USB host computer to read.
2 System software design
The development of system software includes the development of firmware program of MSP430 and uPD720200, the development of windows driver program of uPD720200 and the development of USB host computer application program. We can use the development kit provided by NEC to greatly shorten the development cycle and improve development efficiency.
The MSP430 firmware program mainly completes the control of the A/D chip ADS7886 and the communication with the uPD720200 chip, which transmits the data collected by the ADS7886 chip to the uPD720200. The firmware development of MSP430 needs to define the corresponding pins and timings. For this reason, we use C51 language to write, and the development environment is Keil uVision4.0. The main function of the uPD720200 firmware program is to allow it to transmit the data from the MSP430 chip to the upper computer to achieve ultra-high-speed data transmission. The uPD 720200 fully complies with the USB3.0 protocol, and the firmware program mainly sets and operates its internal control registers. NEC provides the powerful uPD720200 SDK development kit for developers, which can easily develop its firmware and Windows drivers. In the development of the application program of the host computer, NEC also provides users with the corresponding C++ programming interface library functions with simple operation and powerful functions. We choose Microsoft Visual Studio 2008 as the development tool, transmit data through the corresponding library functions and device drivers, and realize the real-time data acquisition function.
This paper introduces in detail the use of uPD720200 as the interface USB3.0 chip and MSP430 as the main control chip, and designs and develops a set of USB3.0 temperature acquisition and transmission system. NEC provides a complete SDK development kit for uPD720200, which shortens the development cycle. The MSP430 series microcontroller we use is driven by a 25MHz crystal to achieve an instruction cycle of 40ns, coupled with a 16-bit data width, its operation speed is very fast compared to the traditional 51 series microcontroller, which can give full play to the bandwidth of USB 3.0. Although affected by the sampling rate of the ADS7886 chip, no super-speed data acquisition is realized, but the combination of MSP430 and uPD720200 is undoubtedly a low-cost and high-efficiency excellent solution for the development of high-speed data acquisition systems.