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magnet999999 发表于 2015-7-17 15:20:22

如何把float转换成char

本帖最后由 magnet999999 于 2015-7-17 15:23 编辑

我用的TM1650LED数字模块，不能把计算出的数据直接显示，需要按照下面的格式才能行TM1650 displayString(char *aString);
但是计算出的数据是float类型的，我该怎么转换。
原程序如下
int dustPin=A0;
int dustVal=0;

int ledPower=2;
int delayTime=280;
int delayTime2=40;
float offTime=9680;
void setup(){
Serial.begin(9600);
pinMode(ledPower,OUTPUT);
//pinMode(4, OUTPUT);
}

void loop(){
// ledPower is any digital pin on the arduino connected to Pin 3 on the sensor
digitalWrite(ledPower,LOW); // power on the LED
delayMicroseconds(delayTime);
dustVal=analogRead(dustPin); // read the dust value via pin 5 on the sensor
delayMicroseconds(delayTime2);
digitalWrite(ledPower,HIGH); // turn the LED off
delayMicroseconds(offTime);

delay(3000);
Serial.println(dustVal);


float dustVal2=dustVal;
dustVal2=(dustVal2*5/1024-0.0356)*120000;
Serial.println(dustVal2);//实际的颗粒数

if(dustVal2<76)
{
Serial.println("EXCELLENT");
}
else if(dustVal2<151)
{
Serial.println("VERY GOOD");
}
else if(dustVal2<301)
{
Serial.println("GOOD");
}
else if(dustVal2<1051)
{
Serial.println("FAIR");
}
else if(dustVal2<3001)
{
Serial.println("POOR");
}
else
{
Serial.println("VERY POOR");
}


if(dustVal>118)
//此拟合公式有效y=0.172*x-0.0999
{
float dustVal3=dustVal;
dustVal3=((dustVal3*5/1024)*0.172-0.0999)*1000;
Serial.println("PM2.5:");
Serial.println(dustVal3);//实际的颗粒数
}
else
{
Serial.println("PM2.5:");
Serial.println("----");
}



}

我修改的程序


#include <Wire.h>
#include <TM1650.h>
char s;
float dustVal3;
int dustPin=A0;
int dustVal=0;

int ledPower=2;
int delayTime=280;
int delayTime2=40;
float offTime=9680;
void setup(){
Serial.begin(9600);
pinMode(ledPower,OUTPUT);
//pinMode(4, OUTPUT);
}

void loop(){
// ledPower is any digital pin on the arduino connected to Pin 3 on the sensor
digitalWrite(ledPower,LOW); // power on the LED
delayMicroseconds(delayTime);
dustVal=analogRead(dustPin); // read the dust value via pin 5 on the sensor
delayMicroseconds(delayTime2);
digitalWrite(ledPower,HIGH); // turn the LED off
delayMicroseconds(offTime);

delay(3000);
Serial.println(dustVal);


float dustVal2=dustVal;
dustVal2=(dustVal2*5/1024-0.0356)*120000;
Serial.println(dustVal2);//实际的颗粒数

if(dustVal2<76)
{
Serial.println("EXCELLENT");
}
else if(dustVal2<151)
{
Serial.println("VERY GOOD");
}
else if(dustVal2<301)
{
Serial.println("GOOD");
}
else if(dustVal2<1051)
{
Serial.println("FAIR");
}
else if(dustVal2<3001)
{
Serial.println("POOR");
}
else
{
Serial.println("VERY POOR");
}


if(dustVal>118)
//此拟合公式有效y=0.172*x-0.0999
{
dustVal3=((dustVal3*5/1024)*0.172-0.0999)*1000;
Serial.println("PM2.5:");
String dataString;
dataString=dtostrf(dustVal3,3.0,s);
TM1650 displayString(dataString);//实际的颗粒数
}
else
{
Serial.println("PM2.5:");
Serial.println("----");
}



}

liuxue4503 发表于 2015-7-17 16:26:04

有个更好用的：sprintf
char *displayString=new char;
float data=333.3333;
sprintf( displayString, "%f", data );

mondaywoo 发表于 2015-7-18 16:24:18

初学者学习

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