An approach based on DSP software radio modulation and demodulation experiment platform (1)

Abstract: design and implementation of a set of software based on software defined radio MODEM of experimental system, the system hardware to TMS320C6711 digital signal processor (DSP) core, multi-standard software radio modulation and demodulation functionality and design of hardware interface complete real-time communication with the host.

In host design virtual instrument control display platform that enables real-time modulation standard and real-time display of measured data.

Keywords: software defined radio; virtual instrument; DSP; MODEM

The basic idea of software radio is an open, scalable, structure minimalist hardware to a common platform, put as many communication functions available to upgrade, you can replace the software.

Its central idea is to construct a standardized, modular universal hardware platform, and through software loading for various wireless communication features an open architecture. Modem is the key technology of software radio, is a software radio technology study of one of the core content, modem software is the realization of software radio openness, versatility is the key step.

System principle

This system is designed for university teaching to TMS320C6711 digital signal processor (DSP) core build software radio teaching demonstration platform, to the fullest embodiment of the design concept of software radio, hardware platform on DSP to build enables hardware's modular, open and programmability, send and receive data through hardware, magnify, in DSP programming FM, DSB, QPSK, QAM, and other systems of modulation and demodulation functionality.

System best feature is the use of general-purpose computer and DSP processing unit combined programmes, a variety of human-machine interface and control capabilities, storage capabilities of the PC, instead of a variety of tasks to complete real time DSP, giving full play to the Office of the high speed DSP

Mathematical ability and flexibility of a PC.

System structure

The system structure as shown in Figure 1.

It is made of DSP data processing Board and PC man-machine interface control the foreground. Which DSP data processing Board for DSP (digital signal processor) as the core microprocessor core, external data transceiver device and DSP peripherals device, send the device for data receiving external signal acquisition and output, through the amplifier will useful signal amplification, the DSP-digital signal processing chip, so further

　　

　　

Figure 1 system architecture diagram

Need A/D and D/A conversion circuit, the acquisition of analog signals into digital signals, and the processing of digital signals into analog signals output.

To meet the host and peripheral hardware of the communication, to use DSP and host interface, we pass in hardware HPI (host interface) implementation of DSP and PC real-time communication. In the PC software designed for use in virtual instrument control display platform, realizing on hardware processing control and display, users can virtual instrument platforms enter data in the front panel to select various modulation format, and data communication interfaces to data into PC, virtual instrument display platform to graphically display the data in the results in real time.

TMS320C6711 chip introduction

Since the modem design implementation is based on TI's TMS320C6711 chip, here on TMSC67x series CPU structure overview.

TMSC67x series CPU internal including program fetch unit, program execution, chip test and simulation port and control logic. Program fetch unit by the program bus and on-chip program memory. Program execution agencies including 2 symmetric data channel (A and B), 2 symmetric general-purpose registers, 2 group symmetry of functional units (each set of four), control register groups and control logic and interrupt logic, etc. Each set of data access are read and stored (write) data bus is connected with on-chip memory.

TMSC67x series CPU use Harvard architecture, its program bus and data bus, take the directives and the implementation of the directive can be run in parallel.

C67x series chip program bus width is 256bit, each fetch operations are to take 8 instruction, known as a fetch packages. Piece of memory and bus without distinction, they are unified. All storage space (including program memory and data memory, on-chip and the Tablet) in bytes, of the unity of the addressed.

Host communication interface design

System host communication interface HPI is a TI company digital signal processor (DSP) for, and host two-way data communication of 8-bit parallel interface.

HPI is called the host interface, is a TI company, high-performance DSP configuration to communicate with a host of on-chip peripherals. Traditional single-chip and the host (such as PC) interface, you need to attach the movie scale out. If you use and how the host shared RAM, RAM chip scale out and trigger, latches and other chips, then the host can use DMA mode randomly or block access to shared RAM; if you do not require random access from host machine data, and may also take the extended FIFO ICS.

In addition, when you need from the machine is interrupted, the film, at least it will extend a latch.

HPI host interface to these functions integrated in the DSP chip inside the host connection is simplified, there is no need for DSP system chip scale out the above purposes.

HPI has two working mode, common address way (SAM) and only host addressing mode (HOM), this system uses a common addressing mode, host and DSP can be addressed to the HPI storage, host DSP convey the control word and [1] [2] [3]