CSDN話題挑戰(zhàn)賽第2期
參賽話題：學(xué)習(xí)筆記
1、整體設(shè)計(jì)
有一天，我在瀏覽CSDN時(shí)看到一篇關(guān)于 AD9850 的帖子。AD9850是一款可以產(chǎn)生1hz到40mhz左右正弦波的芯片。淘寶的產(chǎn)品經(jīng)銷商能夠?qū)⑿酒c提供 TTL 電平控制的小板配對(duì)，然后以令人難以置信的 60元（或更低?。┑膬r(jià)格出售。
要控制 AD9850，您需要某種微控制器。無需過多詳細(xì)說明，您需要向芯片發(fā)送一組串行或并行數(shù)據(jù)來設(shè)置頻率。網(wǎng)上有很多帖子詳細(xì)說明了如何做到這一點(diǎn)，所以我不會(huì)詳細(xì)介紹。然而，很難找到一個(gè)好的 AD9850 引腳排列，所以你去吧。
2、硬件方案
GND = 地；Vss
CLK = 串行編程時(shí)鐘
Latch = 串行編程鎖存器（9850 上的 FQ_UD 引腳）
DATA = 串行編程 DATA（內(nèi)部連接到 D7）
RST = 復(fù)位。保持連接到 GND
SQW = 方波輸出（互補(bǔ)） 占空比可通過藍(lán)色電位器調(diào)節(jié)。
SINA = 原始未濾波 AD9850 正弦輸出
SINB = 70 MHz LPF 濾波 AD9850 輸出。
對(duì)我來說，管理 AD9850 的最簡(jiǎn)單方法是使用 Arduino Uno。如果您不了解 Arduino 平臺(tái)，您應(yīng)該查看官方網(wǎng)站www.arduino.cc。我使用 Arduino 好多年了，我已經(jīng)發(fā)現(xiàn)它是一個(gè)很棒的開發(fā)平臺(tái)。如果你是一個(gè)業(yè)余愛好者……你真的不會(huì)出錯(cuò)。
這個(gè)項(xiàng)目正在進(jìn)行中。您應(yīng)該能夠從 Arduino Sketch 中推斷出所有項(xiàng)目的引腳，但如果您有任何問題，請(qǐng)聯(lián)系我。我的原理圖有點(diǎn)粗糙，因?yàn)槲也粌A向于經(jīng)常創(chuàng)建它們，所以如果你發(fā)現(xiàn)任何不合適的東西，請(qǐng)告訴我！
由于有很多請(qǐng)求，我還為 IF（超外差）類型的接收器創(chuàng)建了一個(gè)版本。VFO 現(xiàn)在支持中頻，并且可以切換 Arduino 上一個(gè)模擬輸入的高/低電平。IF 可以是您想要的任何東西，可以是加法或減法。
DDS VFO 的輸出電壓隨頻率而變化，因此如果您需要它在寬范圍 VFO 上輸出恒定電平，您需要在緩沖器中設(shè)計(jì)一個(gè) AGC（或排序）以提供恒定電平輸出. 我已經(jīng)看到一些帶有簡(jiǎn)單運(yùn)算放大器的出色設(shè)計(jì)，它們通過接入反饋電路來實(shí)現(xiàn)這一點(diǎn)。
同時(shí)這個(gè)方案它適用于 nano。注意：Arduino 的 D10 連接到 AD9850 的 DATA 引腳，而不是 D7。
連接后的硬件電路如下：
3、軟件程序
arduino的程序如下：文章來源：http://www.zghlxwxcb.cn/news/detail-638676.html
#include <LiquidCrystal.h>
#include <Rotary.h>
#include <EEPROM.h>
//Setup some items
#define W_CLK 8 // Pin 8 - connect to AD9850 module word load clock pin (CLK)
#define FQ_UD 9 // Pin 9 - connect to freq update pin (FQ)
#define DATA 10 // Pin 10 - connect to serial data load pin (DATA)
#define RESET 11 // Pin 11 - connect to reset pin (RST)
#define pulseHigh(pin) {digitalWrite(pin, HIGH); digitalWrite(pin, LOW); }
Rotary r = Rotary(2,3); // sets the pins the rotary encoder uses. Must be interrupt pins.
LiquidCrystal lcd(12, 13, 7, 6, 5, 4); // I used an odd pin combination because I need pin 2 and 3 for the interrupts.
int_fast32_t rx=7000000; // Starting frequency of VFO
int_fast32_t rx2=1; // variable to hold the updated frequency
int_fast32_t increment = 100; // starting VFO update increment in HZ.
int buttonstate = 0;
String hertz = "100 Hz";
int hertzPosition = 5;
byte ones,tens,hundreds,thousands,tenthousands,hundredthousands,millions ; //Placeholders
String freq; // string to hold the frequency
int_fast32_t timepassed = millis(); // int to hold the arduino miilis since startup
int memstatus = 1; // value to notify if memory is current or old. 0=old, 1=current.
int ForceFreq = 1; // Change this to 0 after you upload and run a working sketch to activate the EEPROM memory. YOU MUST PUT THIS BACK TO 0 AND UPLOAD THE SKETCH AGAIN AFTER STARTING FREQUENCY IS SET!
void setup() {
Serial.begin(9600);
Serial.println("Start...");
pinMode(A0,INPUT); // Connect to a button that goes to GND on push
digitalWrite(A0,HIGH);
lcd.begin(16, 2);
r.begin();
PCICR |= (1 << PCIE2);
PCMSK2 |= (1 << PCINT18) | (1 << PCINT19);
sei();
pinMode(FQ_UD, OUTPUT);
pinMode(W_CLK, OUTPUT);
pinMode(DATA, OUTPUT);
pinMode(RESET, OUTPUT);
pulseHigh(RESET);
pulseHigh(W_CLK);
pulseHigh(FQ_UD); // this pulse enables serial mode on the AD9850 - Datasheet page 12.
Serial.println("DDS v1.0.0");
lcd.clear();
lcd.setCursor(hertzPosition,1);
lcd.print(hertz);
// Load the stored frequency
if (ForceFreq == 0) {
freq = String(EEPROM.read(0))+String(EEPROM.read(1))+String(EEPROM.read(2))+String(EEPROM.read(3))+String(EEPROM.read(4))+String(EEPROM.read(5))+String(EEPROM.read(6));
rx = freq.toInt();
Serial.println(rx);
}
}
void loop() {
if (rx != rx2){
showFreq();
sendFrequency(rx);
rx2 = rx;
}
buttonstate = digitalRead(A0);
if(buttonstate == LOW) {
setincrement();
};
// Write the frequency to memory if not stored and 20 seconds have passed since the last frequency change.
if(memstatus == 0){
if(timepassed+20000 < millis()){
storeMEM();
}
}
}
ISR(PCINT2_vect) {
unsigned char result = r.process();
if (result) {
if (result == DIR_CW){rx=rx+increment;}
else {rx=rx-increment;};
if (rx >=30000000){rx=rx2;}; // UPPER VFO LIMIT
if (rx <=500000){rx=rx2;}; // LOWER VFO LIMIT
}
}
// frequency calc from datasheet page 8 = <sys clock> * <frequency tuning word>/2^32
void sendFrequency(double frequency) {
int32_t freq = frequency * 4294967295/125000000; // note 125 MHz clock on 9850. You can make 'slight' tuning variations here by adjusting the clock frequency.
for (int b=0; b<4; b++, freq>>=8) {
tfr_byte(freq & 0xFF);
}
tfr_byte(0x000); // Final control byte, all 0 for 9850 chip
pulseHigh(FQ_UD); // Done! Should see output
}
// transfers a byte, a bit at a time, LSB first to the 9850 via serial DATA line
void tfr_byte(byte data)
{
for (int i=0; i<8; i++, data>>=1) {
digitalWrite(DATA, data & 0x01);
pulseHigh(W_CLK); //after each bit sent, CLK is pulsed high
}
}
void setincrement(){
if(increment == 1){increment = 10; hertz = "10 Hz"; hertzPosition=5;}
else if(increment == 10){increment = 50; hertz = "50 Hz"; hertzPosition=5;}
else if (increment == 50){increment = 100; hertz = "100 Hz"; hertzPosition=4;}
else if (increment == 100){increment = 500; hertz="500 Hz"; hertzPosition=4;}
else if (increment == 500){increment = 1000; hertz="1 Khz"; hertzPosition=6;}
else if (increment == 1000){increment = 2500; hertz="2.5 Khz"; hertzPosition=4;}
else if (increment == 2500){increment = 5000; hertz="5 Khz"; hertzPosition=6;}
else if (increment == 5000){increment = 10000; hertz="10 Khz"; hertzPosition=5;}
else if (increment == 10000){increment = 100000; hertz="100 Khz"; hertzPosition=4;}
else if (increment == 100000){increment = 1000000; hertz="1 Mhz"; hertzPosition=6;}
else{increment = 1; hertz = "1 Hz"; hertzPosition=5;};
lcd.setCursor(0,1);
lcd.print(" ");
lcd.setCursor(hertzPosition,1);
lcd.print(hertz);
delay(250); // Adjust this delay to speed up/slow down the button menu scroll speed.
};
void showFreq(){
millions = int(rx/1000000);
hundredthousands = ((rx/100000)%10);
tenthousands = ((rx/10000)%10);
thousands = ((rx/1000)%10);
hundreds = ((rx/100)%10);
tens = ((rx/10)%10);
ones = ((rx/1)%10);
lcd.setCursor(0,0);
lcd.print(" ");
if (millions > 9){lcd.setCursor(1,0);}
else{lcd.setCursor(2,0);}
lcd.print(millions);
lcd.print(".");
lcd.print(hundredthousands);
lcd.print(tenthousands);
lcd.print(thousands);
lcd.print(".");
lcd.print(hundreds);
lcd.print(tens);
lcd.print(ones);
lcd.print(" Mhz ");
timepassed = millis();
memstatus = 0; // Trigger memory write
};
void storeMEM(){
//Write each frequency section to a EPROM slot. Yes, it's cheating but it works!
EEPROM.write(0,millions);
EEPROM.write(1,hundredthousands);
EEPROM.write(2,tenthousands);
EEPROM.write(3,thousands);
EEPROM.write(4,hundreds);
EEPROM.write(5,tens);
EEPROM.write(6,ones);
memstatus = 1; // Let program know memory has been written
Serial.println(rx);
};
4、實(shí)物驗(yàn)證
文章來源地址http://www.zghlxwxcb.cn/news/detail-638676.html
到了這里，關(guān)于基于STM32單片機(jī)和AD9850的智能DDS函數(shù)信號(hào)發(fā)生器的文章就介紹完了。如果您還想了解更多內(nèi)容，請(qǐng)?jiān)谟疑辖撬阉鱐OY模板網(wǎng)以前的文章或繼續(xù)瀏覽下面的相關(guān)文章，希望大家以后多多支持TOY模板網(wǎng)！
