0 Introduction In the field of electronic technology, oscilloscopes are widely used. It can be used to easily and intuitively observe the whole picture and measure the basic parameters such as amplitude, frequency and period of the signal. The traditional analog oscilloscope shows that the afterglow time of the fluorescent substance is constant, which makes it difficult to observe the signal with a long period. In addition, analog oscilloscopes are not able to perform some special mathematical processing (such as FFT) on the signal. Digital oscilloscopes can overcome the shortcomings of analog oscilloscopes, using a variety of advanced measurement techniques to meet a variety of applications. For example, based on the sampling principle, high-speed A/D converter is used for high-speed data acquisition, the analog signal is digitized, and then various digital signal processing algorithms are realized by the powerful data processing capability of the processor, and the waveform is visually displayed in a graphical manner. And can get a variety of parameters of the signal under test. [3] Hydraulic Servo Systems,Servo System Harness,Hydraulic Bldc Motor,Servo Motor Pump Zhejiang Synmot Electrical Technology Co., Ltd , https://www.synmot-electrical.com
1 System overall scheme The system block diagram of this design is shown in Figure 1. Thanks to the flexibility of the FPGA, most of the functions of the system are completed inside the FPGA, making the overall structure very simple. The peripheral circuits mainly include an A/D conversion module, an LCD display, an SD card, a FLASH, and a button.
The function of the A/D conversion module is to realize the conversion of the analog signal to the digital signal; the function of the FLASH module is to store the firmware program of the SoPC (System-on-a-Programmable-Chip) system on chip; the function of the SD card module is to realize the measurement information. The long-term, large-scale storage provides an interface with the PC for later analysis on the computer; the function of the LCD module is real-time display of the measured signal waveform and related parameters; the function of the button module is to provide the adjustment and control interface of the whole machine. .
2 FPGA logic function module design
The internal system block diagram of FPGA is shown in Figure 2. It is mainly composed of a sampling rate controller, a trigger control unit, a FIFO controller, a frequency measuring unit, a button control unit, and an LCD driver.
3 SoPC Design This design uses the Nios II/f processor, which uses a hardware multiplier to operate at 50 MHz. Use the RAM block embedded in the FPGA as the running memory of the system. Using FLASH as the off-chip memory, the user program is saved, which is connected to the Nios II processor through the Avalon bus tri-state bridge.
3.1 SoPC software design system After calling the relevant function to initialize the LCD, SD card and FAT file system, first draw the graphical interface, output the fixed information, then read the waveform parameters, display it on the LCD, and then wait for the FIFO to fill. If the FIFO is full, the FIFO data is read into the buffer, and the waveform is drawn on the screen to obtain the maximum and minimum values ​​of the waveform. Finally, if there is user input, the button event is processed. Otherwise, the waveform parameter is detected to change. If there is any change, the display is updated. Otherwise, the FIFO is full and the next display is performed. The process is shown in Figure 3.
3.1.1 SoPC underlying software design The underlying software is the driver for each device, mainly:
(1) LCD driver. According to the requirements of the display content, the LCD driver designed the following functions:
1 send data / command: send data / command to the LCD through the drive;
2LCD initialization: complete the power-on reset and initialization of the LCD;
3LCD clear screen: clear display;
4 output one pixel: output a pixel of a specified color at a specified position;
5 draw a straight line: draw a line from (x0, y0) to (x1, y1) the specified color;
6 draw rectangle: draw a rectangle from (x0, y0) to (x1, y1) the specified color, you can choose whether to fill;
7 output a character: output a character of the specified color at the specified position;
8 Output a string: Output a string of the specified color at the specified position.
(2) SD card driver. The SD card communication adopts the SPI mode, and the functions and functions of the SD card driver are:
1 send data / command: send data / command to the SD card;
2 read data: read a byte from the SD card;
3SD card reset: SD card is reset after power-on and puts it into SPI mode;