The variable increase 1 trouble

Projects Programming
1

Hi All

I meet the problem with the variable when I increase it to 1.

UNO board +1 button.

This is code :

#include <EEPROM.h>

#define START 6

float chuoi[]={};
float num=0;
int pos=0;
int bien=0;
int i=0;

void setup() 
{
  pinMode(START,INPUT);
  digitalWrite(START,HIGH);
  Serial.begin(115200);
}
void addtoado()
{
 for(i;i<=5;i++)
  {
    num=i+0.5;
    EEPROM.put(i*sizeof(num),num);
    delay(5);
    Serial.print("num=");
    Serial.println(num);
  } 
}
void laytoado()
 {
  EEPROM.get(pos*sizeof(num),chuoi[pos]); // foat size 4 byte
  Serial.print("chuoi[pos]=");
  Serial.println(chuoi[pos]);
 }
void loop() 
{
  bien=digitalRead(START);
  if(bien==0)
  {
   delay(500);
   addtoado();
   Serial.print("posold=");
   Serial.println(pos);
   laytoado();
   pos++;
   Serial.print("posnew=");
   Serial.println(pos);
   if(pos>5)
   {
    pos=0; 
   }
  }
}

First press : The monitor display posnew =1 // correct

Second press : posnew =16321 ( WHY ???? , increase 1 ???? )

Third press : return the first press ( ??? )

Please HELP !

posnew correct.JPG

posnew wrong.JPG

2 
float chuoi[]={};

This is not allowed in C++. If GCC compiler permitted this to slip through as a non-standard extension, then you ended up with an array of size 0. You are not allowed to access elements of such array - they don't exist.

Yet you are happily doing it in your code. Your code has undefined behavior.

3

You may get into problems if you execute this statement more than once.

for(i;i<=5;i++)
4

Dear Montmorency

I'm done. It simple , but i don't attention. Thanks very much ! :slight_smile: :slight_smile: :slight_smile: :slight_smile:

Dear david_2018

Thanks ! But I think i don't reset " i " .The loop "for" not working for the second.

5

Please at least post your solution so others can learn :slight_smile:

6

Oh Sorry !

This code final , it working ok . thanks all !

#include <EEPROM.h>

#define START 6

float chuoi[5];     // ^_^
float num=0;
int pos=0;
int bien=0;
int i=0;

void setup() 
{
  pinMode(START,INPUT);
  digitalWrite(START,HIGH);
  Serial.begin(115200);
}
void addtoado()
{
 for(i;i<=5;i++)
  {
    num=i+0.5;
    EEPROM.put(i*sizeof(num),num);
    delay(5);
    Serial.print("num=");
    Serial.println(num);
  } 
}
void laytoado()
 {
  EEPROM.get(pos*sizeof(num),chuoi[pos]); // foat size 4 byte
  Serial.print("chuoi[pos]=");
  Serial.println(chuoi[pos]);
 }
void loop() 
{
  bien=digitalRead(START);
  if(bien==0)
  {
   delay(500);
   addtoado();
   Serial.print("posold=");
   Serial.println(pos);
   laytoado();
   pos++;
   Serial.print("posnew=");
   Serial.println(pos);
   if(pos>5)
   {
    pos=0; 
   }
  }
}
7 
 for(i;i<=5;i++)

The first clause of a for loop is the initialization clause. i doesn't initialize anything. i = 0 does.