Design of Signal Generator Based on FPGA and 51 Single Chip Microcomputer

Signal generator, also known as waveform generator, is a commonly used signal source and one of the important instruments widely used in the fields of electronic circuits, communications, control and teaching experiments. In order to reduce the cost of traditional function signal generators and improve the low-frequency stability of signal generators. The author combines FPGA and 51 single-chip microcomputer to generate 0.596 Hz frequency accuracy function signal. The author designed to control the function signal type and related parameters through the 51 single-chip microcomputer. Users can set the required waveform, waveform amplitude, waveform frequency, and square wave duty cycle and phase through buttons. The design scheme in this paper not only has good economic prospects, but also can serve as a reference direction for deepening the reform of contemporary higher education.

1 System Design

1.1 System Hardware Design

The hardware in this paper includes EP2C8Q20818N chip, C8051F0201 microcontroller, DAC0800 chip, and T6963 LCD. In this paper, FPGA (EP2C8Q20818N) is mainly used to bridge control LCD, 4×4 keyboard and DAC0800 (C8051 microcontroller and DAC0800 have a reference voltage signal), and the system hardware design block diagram is shown in Figure 2. In this paper, the function signal is mainly generated by FPGA (EP2C8Q20818N); C8051 microcontroller is used to analyze and process user information, provide reference voltage to DAC0800, and control FPGA (EP2C8Q20818N) to generate the function signal required by the user.

1.1.1 EP2C8Q20818N Introduction

EP2C8Q20818N is an embedded FPGA (field programmable gate array) chip launched by ALTERA. It has 182 pins. Its characteristics are listed below, as shown in Figure 1.

1.1.2 C8051F0201 Introduction

The C8051F0201 (hereinafter referred to as the 51 microcontroller) device is a fully integrated mixed-signal system-level MCU chip with 32 digital I/O pins. This 51 microcontroller has a high-speed, pipelined 8051-compatible CIP-51 core (up to 25 MIPS). Full-speed, non-intrusive in-system debug interface (on-chip). 12-bit, 100 ksps 8-channel ADC with PGA and analog multiplexer. 8-bit 500 ksps ADC with PGA and 8-channel analog multiplexer Two 12-bit DACs with programmable data update mode. 64 K bytes of FLASH memory that can be programmed in the system. 4 352 (4 096+256) bytes of on-chip RAM, external data memory interface that can address 64 k bytes of address space. Hardware-implemented SPI, Sm Bus/I2C and two UART serial interfaces, 5 general-purpose 16-bit timers. Programmable counter/timer array with 5 capture/compare modules. With an on-chip watchdog timer, VDD monitor, and temperature sensor, each MCU can operate with a voltage of 2.7 to 3.6 V over the industrial temperature range (-45 to +85°C). The port I/O, /RST, and JTAG pins all tolerate 5 V input signal voltages.

1.2 C8051 MCU Software Design

The C8051 microcontroller software mainly includes key processing function, signal generator control function, initialization function, LCD display function, D/A function and main function. The main program flow chart of the software design is shown in Figure 3, and the detailed functions of the sub-functions are shown in Table 1.

1.3 FPGA (EP2C8Q20818N) software design

This article mainly uses Verilog HDL language design. It mainly includes chip selection module, clock drive module, keyboard scanning module, outgoing signal module, LCD module, DAC0800 module and indicator light module. The detailed functions are shown in Table 2.

1.4 FPGA core program code, DAC0800 module program

2 Test Results

3 Conclusion

In this article, FPGA and 51 single-chip microcomputer are combined to make a signal generator. This can not only train students to use single-chip microcomputers and FPGAs, but also allow students to learn how to use FPGA and single-chip microcomputers for joint communication. In this design, the accuracy of function signals can be upgraded to meet the function signal requirements of different occasions. This article advocates a learning method that combines single-chip microcomputers and FPGAs, which can provide a reference direction for modern education reform.