Wierd Serial Read result!! I don't know why this doesn't work!! (EEPROM)

Angelacat · December 21, 2015, 3:51pm

Hi All,

I try to use following code to control the "read" and "write" of EEPROM.

Basically, I want to be able to type "write 3 10" in the serial monitor and save number 10 into the location 3 of EEPROM and when I type "read 3" it should print out 10 (the number that store in location 3).

My code compiled well but it runs funny...

I am able to store the "read" "location" and "number" into different variables and convert them into string, int, int, respectively.

However, the part with read & writing into EEPROM doesn't go well!!

Somehow the program cannot store the number into correct location and that after I type in "write 10 12" (for example), the next time I type "read 10", the Serial print gives me "reade 10" instead of "read 10". Also, it cannot get the correct number back.

I just cannot see what has gone wrong with my code. I imaging its some problem with the start/end of the serial read or some problem with the leftover serial input.

Thanks in advance for any suggestions!

#include <EEPROM.h>

char commend[20];
char rw[20];
char location[20];
char number[20];
int l;
int n;
String RW;
int value;

void setup() {
Serial.begin(9600);
}

void loop() {

if (Serial.available() > 0)
{
Serial.readBytesUntil(' ',rw, 20);
Serial.readBytesUntil(' ',location, 20);
Serial.readBytesUntil(' ',number, 20);
Serial.println(rw);
Serial.println(location);
Serial.println(number);
int l = atoi(location);
int n = atoi(number);
RW = String(rw);
Serial.println(l);
Serial.println(n);

}

if (RW == "read"){
value = EEPROM.read(l);
Serial.println(value);
}

if (RW == "write"){
EEPROM.write(l,n);

}

system · December 21, 2015, 4:15pm

Serial.println(rw);
Serial.println(location);
Serial.println(number);

Anonymous printing sucks. Print some identifiers before and after these "strings" and you will see that they are NOT strings. A string is a NULL terminated array of chars. These arrays are NOT NULL terminated.

Angelacat · December 21, 2015, 4:21pm

Hi Paul,

Thanks for your fast reply!

Do you know how I can fix this?

system · December 21, 2015, 4:26pm

Do you know how I can fix this?

Yes. Look at the documentation for the readBytesUntil() function. It returns the number of bytes actually placed in the array. Add a NULL to the array, after that number of bytes.

  byte byteCount = Serial.readBytesUntil(' ',rw, 20);
  nw[byteCount] = '\0';

Angelacat · December 21, 2015, 4:32pm

Thanks Paul!

I'll try it out tonight and see how it goes!

Does other parts of my code looks okay?

Do you think this is the only issue with my code?

system · December 21, 2015, 4:43pm

Does other parts of my code looks okay?

Except for the use of the String class, yes.

Do you think this is the only issue with my code?

If you go to the doctor with a hangnail on you middle finger, after nearly cutting you are off in a chainsaw accident, do you think the doctor is going to treat the hangnail?

Fix the obvious, major, issues first.

Angelacat · December 21, 2015, 5:19pm

Got it! Thanks again, Paul!

Angelacat · December 22, 2015, 3:23am

Hi Paul,

I have changed my code to the following and still doesn't work~

#include <EEPROM.h>

char commend[20];
char rw[20];
char location[20];
char number[20];
int l;
int n;
String RW;
int value;
int byteCount1;
int byteCount2;
int byteCount3;

void setup() {
Serial.begin(9600);
}

void loop() {

while(!Serial.available()) ;
if (Serial.available() > 0)
{
Serial.readBytesUntil(' ',rw, 20);
byteCount1 = Serial.readBytesUntil(' ',rw, 20);
rw[byteCount1] = '\0';
Serial.readBytesUntil(' ',location, 20);
byteCount2 = Serial.readBytesUntil(' ',location, 20);
location[byteCount2] = '\0';
Serial.readBytesUntil(' ',number, 20);
byteCount3 = Serial.readBytesUntil(' ',number, 20);
number[byteCount3] = '\0';
int l = atoi(location);
int n = atoi(number);
RW = String(rw);
Serial.println(RW);
Serial.println(l);
Serial.println(n);
}

if (RW == "read"){
value = EEPROM.read(l);
Serial.println(value);
}

if (RW == "write"){
EEPROM.write(l,n);
}

}

system · December 22, 2015, 10:18am

I have changed my code to the following and still doesn't work

The code does something. It gets some data and prints some data to the serial port. I do not think it is unrealistic for us to expect you to explain what it does and show what it prints.

Angelacat · December 22, 2015, 2:49pm

PaulS:
The code does something. It gets some data and prints some data to the serial port. I do not think it is unrealistic for us to expect you to explain what it does and show what it prints.

Hi Paul,

I tried the following code, but now when I type "write 12 10", instead of giving me:

Write
12
10

It gives me:
12
0
0

And when I type "read 12"

It still gives me:

12
0
0

Please let me know what I did wrong. Thanks!

#include <EEPROM.h>

char commend[20];
char rw[20];
char location[20];
char number[20];
int l;
int n;
String RW;
int value;
byte byteCount1;
byte byteCount2;
byte byteCount3;

void setup() {
Serial.begin(9600);
}

void loop() {

while(!Serial.available()) ;
if (Serial.available() > 0)
{
Serial.readBytesUntil(' ',rw, 20);
byte byteCount1 = Serial.readBytesUntil(' ',rw, 20);
rw[byteCount1] = '\0';
Serial.readBytesUntil(' ',location, 20);
byte byteCount2 = Serial.readBytesUntil(' ',location, 20);
location[byteCount2] = '\0';
Serial.readBytesUntil(' ',number, 20);
byte byteCount3 = Serial.readBytesUntil(' ',number, 20);
number[byteCount3] = '\0';
int l = atoi(location);
int n = atoi(number);
RW = String(rw);
Serial.println(RW);
Serial.println(l);
Serial.println(n);
}

if (RW == "read"){
value = EEPROM.read(l);
Serial.println(value);
}

if (RW == "write"){
EEPROM.write(l,n);
}

}

system · December 22, 2015, 4:14pm

Serial.readBytesUntil(' ',rw, 20);
  byte byteCount1 = Serial.readBytesUntil(' ',rw, 20);
  rw[byteCount1] = '\0';
Serial.readBytesUntil(' ',location, 20);
  byte byteCount2 = Serial.readBytesUntil(' ',location, 20);
  location[byteCount2] = '\0';
Serial.readBytesUntil(' ',number, 20);
  byte byteCount3 = Serial.readBytesUntil(' ',number, 20);
  number[byteCount3] = '\0';

Read everything until a space appears. Put that in rw, so rw contains "write".

Then, read everything until another space appears, and put that in rw, so rw contains "10", but this time count the bytes so you can NULL terminate the string.

Can you see that that way lies madness?

Angelacat · December 22, 2015, 4:50pm

Got it. You mean I shouldn't do the serial.readbyteUntil() twice?

Angelacat · December 22, 2015, 5:08pm

Hi Paul,

Thanks many for your advice!

I have changed my code to the following. Now, when I type "write 12 10"

it prints:

write
12
10

But when I type "read 12"

It gives me:

It seems that it still cannot save the number 10 into position 12.

Do you know why?

Thanks!!!

#include <EEPROM.h>

char commend[20];
char rw[20];
char location[20];
char number[20];
int l;
int n;
String RW;
int value;
byte byteCount1;
byte byteCount2;
byte byteCount3;

void setup() {
Serial.begin(9600);
}

void loop() {

while(!Serial.available()) ;
if (Serial.available() > 0)
{
byte byteCount1 = Serial.readBytesUntil(' ',rw, 20);
rw[byteCount1] = '\0';
byte byteCount2 = Serial.readBytesUntil(' ',location, 20);
location[byteCount2] = '\0';
byte byteCount3 = Serial.readBytesUntil('\n',number, 20);
number[byteCount3] = '\0';
int l = atoi(location);
int n = atoi(number);
RW = String(rw);
Serial.println(RW);
Serial.println(l);
Serial.println(n);
}

if (RW == "read"){
value = EEPROM.read(l);
Serial.println(value);
}

if (RW == "write"){
EEPROM.write(l,n);
}

}

cattledog · December 22, 2015, 6:55pm

#include <EEPROM.h>

char commend[20];
char rw[20];
char location[20];
char number[20];
int l;
int n;
String RW;
int value;
byte byteCount1;
byte byteCount2;
byte byteCount3;

void setup() {
  Serial.begin(9600);
}


void loop() {

while(!Serial.available()) ;
if (Serial.available() > 0)
  {
  byte byteCount1 = Serial.readBytesUntil(' ',rw, 20);
  rw[byteCount1] = '\0';
  byte byteCount2 = Serial.readBytesUntil(' ',location, 20);
  location[byteCount2] = '\0';
  byte byteCount3 = Serial.readBytesUntil('\n',number, 20);
  number[byteCount3] = '\0';  
int l = atoi(location);
int n = atoi(number);
RW = String(rw);
Serial.println(RW);
Serial.println(l);
Serial.println(n);
}


if (RW == "read"){
value = EEPROM.read(l);
Serial.println(value);
}

if (RW == "write"){
EEPROM.write(l,n);
}

}

It really is not hard to post using code tags. The redeclaration of l and n within the serial input block has them at 0 value in the read/write blocks.

//int l = atoi(location);
//int n = atoi(number);

 l = atoi(location);
 n = atoi(number);

Angelacat · December 22, 2015, 7:10pm

Hi Paul,

Sorry for not posting with the code tag~ I am completely new to Arduino & this forum so didn't notice that. Will do in future.

So what you said is that I should put the converting code out of the Serial block to solve the problem?

I will try it and let you know how it goes!

Thank you!

cattledog · December 22, 2015, 7:19pm

So what you said is that I should put the converting code out of the Serial block to solve the problem?

No. Just don't redeclare l and n. They are already globals.

Angelacat · December 22, 2015, 7:32pm

Hi Paul,

Now it works! thanks a million!!

Hi Cattledog,

It seems that when I move the converting out from the block. The code works perfectly. I will try without redeclaring l and n to see how it goes later.

Topic		Replies	Views
EEPROM reading and saving via Serial Monitor Storage	10	8819	May 6, 2021
Write / read from EEPROM not output correct values Storage	3	1538	May 6, 2021
EEPROM, writing and reading from any position Storage	2	787	May 6, 2021
EEPROM reading - writing string[SOLVED]! Storage	10	10280	May 6, 2021
EEPROM reading values problem[SOLVED]!! Storage	13	16021	May 6, 2021

Wierd Serial Read result!! I don't know why this doesn't work!! (EEPROM)

Related topics