【正文】 專用芯片，并由單片機控制合成信號源，設計的技術指標如下： ●頻率范圍 ～ 。 DDS(直接數(shù)字式頻率合成技術 )出現(xiàn)于 20 世紀 70 年代，它是一種全數(shù)字頻率合成技術， 完全沒有振蕩元件和鎖相環(huán)，采用一連串數(shù)據(jù)流經(jīng)過 D/A轉換器產(chǎn)生一個預先設定的模擬信號。 目前廣泛使用的 DDS 芯片很多，本設計采用 AD9835 芯片。在現(xiàn)代電子學的各個領域，常常需要高精度且頻率可方便調節(jié)的信號發(fā)生器。s t design principles and AD9835 DDS chips using method. Output frequency and amplitude of the waveform by the signal generator within a certain range can be arbitrarily changed. Compared with the traditional signal generator with several kinds of output waveform, It has the characteristics of arbitrary waveforms output and high precision and low frequency. Key words DDS， AD9835， STC89C52， Signal Generator 目錄 I 目 錄 摘 要 ............................................................................................................................... I ABSTRACT .................................................................................................................... II 1 緒論 ............................................................................................................................... 1 設計背景 .................................................................................................................... 1 信號發(fā)生器概述 ......................................................................................................... 1 本設計概述 ................................................................................................................ 2 2 硬件電路設計 ...............................................................................................................3 主控 芯片和電路設計 .................................................................................................. 3 單片機介紹 .......................................................................................................... 3 STC89C52 單片機 ................................................................................................. 3 DDS原理和電路設計 .................................................................................................. 8 DDS原理與特點 ................................................................................................... 8 AD9835 原理與結構 .............................................................................................. 9 AD9835 應用電路 ................................................................................................ 14 RS232模塊 ............................................................................................................... 15 RS232 通信協(xié)議介紹 ........................................................................................... 15 RS232 串口硬件電路設計 .................................................................................... 16 4 4矩陣鍵盤 .......................................................................................................... 17 4 4矩陣鍵盤 的工作原理 ................................................................................... 17 LCD液晶顯示模塊 ................................................................................................... 17 液晶顯示介紹 .................................................................................................... 18 LCD1602字符型液晶顯示模塊介紹 ..................................................................... 18 LCD1602參數(shù)及引腳功能 ................................................................................... 19 信號發(fā)生器 .............................................................................................................. 20 系統(tǒng)總電路圖 .................................................................................................... 20 實物制作說明 .................................................................................................... 20 系統(tǒng)實際功能介紹 ............................................................................................. 21 3 軟件程序設計 ............................................................................................................. 23 ...................................................................................................... 23 內部寄存器、控制字和編程 .................................................................... 23 攀枝花學院本科畢業(yè)設計（論文） II 4 4矩陣鍵盤程序設計 ............................................................................................. 29 4 4矩陣鍵盤識別處理 ...................................................................................... 29 LCD1602編程 .......................................................................................................... 31 LCD1602指令說明及時序 ................................................................................... 31 LCD1602 的 RAM 地址映射 ................................................................................ 34 LCD1602一般初始化過程 ................................................................................... 35 串口通信編程 .......................................................................................................... 35 串口控制寄存器 ................................................................................................. 35 波特率計算 ........................................................................................................ 38 串口程序設計 .................................................................................................... 38 信號發(fā)生器軟件函數(shù) ................................................................................................ 40 4 系統(tǒng)調試 ..................................................................................................................... 42 硬件電路調試 ........................................................................................................... 42 軟件調試 ................................................................................................................. 42 實物測試 ................................................................................................................. 43 測試示波器介紹 ...................