Design And Realization Of NAVTEX Receiver Based On Dual-Core DSP

With the development of marine economy,the navigation safety of ships has been paid attention increasingly.The NAVTEX is a system based on narrow-band direct-printing telegraphy--transmitting and automatically receiving safety information for maritime navigation.It is an important component of the Global Maritime Distress and Safety System(GMDSS)and is of vital importance for the safe navigation of ships.The paper analyzes the working principle and technical requirement of NAVTEX system in detail.Combining with the status and characteristics of NAVTEX receivers at home and abroad,The Paper presents the overall scheme of the receiver based on TI's F28M35 dual-core DSP processor as the core controller,accomplishing international or local messages of receiving,storing,displaying and emergency information alerts.The receiver hardware includes radiofrequency receiver module,information processing module,message display module,external communication interface and other parts.Among them,the radiofrequency receiver module uses DDS as the oscillator,which improves the accuracy of the frequency output and is conducive to adjusting the oscillation signal.The information processing module includes the F28M35 chip and the peripheral circuit.Besides the functions of control and data processing,the integrated 12-bit AD completes the conversion of analog signal to digital signal;the message display module is made up the touchable color screen which substitute the traditional interactive keys and receives the control command as the human-interaction-device module while displaying the message;in addition,an SD card is provided for storing the message and a network The interface supports data uploading and other functions.The software part includes functions such as sending control commands to the DDS,digital quadrature demodulation,digital filtering and message decoding,storage and display functions.The master core does complete the display of data and human-computer interaction command analysis and response.The control core realizes the band-pass sampling by controlling the sampling frequency and completes the signal acquisition,digital filtering,demodulation and the control function to the DDS module.Communication between master core and control core by send internal-core IPC interrupt command and set the data buffer in the shared RAM to achieve.Based on the hardware debugging,the software design and actual debugging of each module are done respectively.The feasibility of digital demodulation is verified by simulation and verification.The inter-core communication,LCD display and SD card data storage are verified successfully.Finally,the system will be linked with each module to achieve the correct reception and display NAVTEX message function.