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[on:]

Hi, for a program I'm writing, I am parsing one character at a time from an "    ".read buffer i've set up and storing those as bytes.  However where I'm getting stuck is that I need to combine say three or four bytes into one new byte.  i looked at some of the references on the arduino page and found a little promise in the byte() command but I'm not sure how to setup the syntax for that.  and i dont even know if its the right command.

so for example if i have:

byte data1[] = {1};
byte data2[] = {2};
byte data3[] = {3};

can i do something like:

byte newdata[] = {data1 & data2 & data3};

thanks

[Reply #1 on:]

can i do something like:

No. You could use memcpy to copy an array, or a for loop to copy elements in the array. You need to be sure to allocate a large enough array first.

I need to combine say three or four bytes into one new byte.

This isn't going to happen. Perhaps you left the term array out of the sentence.

A little more detail (some code) on what you are doing would be helpful.

[Reply #2 on:]

basically what i am doing is that i am trying to read in an ip address, parse it, and store it as 4 bytes into the eeprom so that it can be read upon reboot.  so what i have so far at accomplishing that is that i am reading a byte one at a time and storing it into 12 distinct bytes.  so for example:

Code:

byte newIP1 = textBuff[10];
  byte newIP2 = textBuff[11];
  byte newIP3 = textBuff[12];
  byte newIP4 = textBuff[14];
  byte newIP5 = textBuff[15];
  byte newIP6 = textBuff[16];
  byte newIP7 = textBuff[18];
  byte newIP8 = textBuff[19];
  byte newIP9 = textBuff[20];
  byte newIP10 = textBuff[22];
  byte newIP11 = textBuff[23];
  byte newIP12 = textBuff[24];

but then i want to take the first 4 bytes and create a new byte and so on and so forth until i get all four bytes.

such as:
byte1 is read as 1
byte2 is read as 2
byte3 is read as 3

and then the new byte would be:
byte1byte2byte3 otherwise known as 123
so the new byte would have a value of 123 which would then be written to eeprom

is that enough detail?  im tryin to be clear lol

[Reply #3 on:]

I notice that the indexes into the textBuff array are not contiguous. You could make a copy of the textBuff array from 10 through 25. Then change the value that was in 13, 17, 21, and 25 to NULL.

Then create a pointer to point to textCopy[0], and pass that pointer to atoi(). Save the returned integer. Increment the pointer by 4, and repeat, to get all 4 (byte sized) integers.

[Reply #4 on:]

i really do appreciate your help on this but i read that last message over and over again trying to understand what you meant and i still dont fully understand.  would you mind showing me a little sample code? especially on the atoi() command, i couldnt find too much online bout that command.  what do you mean by pointer?  and by copy the buffer do you mean like a memcopy? do you have sample code for that or a place where i can read up on it?

thank you so much

[Reply #5 on:]

Code:

// Create an array to hold the new IP string
byte textCopy[16];

Code:

// Copy the array
for(int i=10, j=0; i<26; i++, j++)
{
   textCopy[j] = textBuff[i];
}

Code:

// Replace the dots with NULLs
textCopy[3] = '\0';
textCopy[7] = '\0';
textCopy[11] = '\0';
textCopy[15] = '\0';

Code:

// Pointer to each field
byte *ptr = textCopy[0]; // Point to first octet

Code:

int octets[4]; // Array of octets

Code:

// Parse the data
for(int i=0; i<4; i++)
{
   octet[i] = atoi(ptr); // Convert octet to integer and store
   ptr += 4; // Advance pointer to next octet
}

[Reply #6 on:]

  byte *ptr = textCopy[0];

I get an error for this code:  invalid conversion from byte to byte
should the asterisk be there?

int octet1[4];
  for(int i=0; i<4; i++)
  {
    octet1 = atoi(ptr);
    ptr +=4;
  }

so this above code is only for the first octet right?

thanks

[Reply #7 on:]

Try this:

Code:

char textCopy[] = { '1', '9', '2', '.',
                    '1', '6', '8', ',',
                    '0', '0', '0', '.',
                    '0', '0', '1', '.'};

int octet[4];

void setup()
{
  Serial.begin(9600);

  textCopy[3] = '\0';
  textCopy[7] = '\0';
  textCopy[11] = '\0';
  textCopy[15] = '\0';
  
  char *ptr = textCopy;
  for(int i=0; i<4; i++)
  {
    Serial.print("ptr points to: [");
    Serial.print(ptr);    Serial.println("]");
    
    octet[i] = atoi(ptr);
    ptr += 4;
  }
  
  for(int i=0; i<4; i++)
  {
    Serial.print("octet[");
    Serial.print(i);    Serial.print("] = ");
    Serial.println(octet[i]);
  }
}

void loop()
{
}

You may need to perform a cast when copying the byte array to the char array, in your code.

[Reply #8 on:]

so i uploaded and tried your code and it worked flawlessly thank you.  so then using your code i put it into my main code but everytime i try and compile it i get a "invalid conversion from 'char to 'char*'" error.  heres the bit of code i entered to my main code:

char textCopy[16];
  for(int i=10, j=0; i<26; i++, j++)
  {
    textCopy[j] = textBuff;
  }
  textCopy[3] = '\0';
  textCopy[7] = '\0';
  textCopy[11] = '\0';
  textCopy[15] = '\0';
  char *ptr = textCopy[0];
  int octet[4];
  for(int i=0; i<4; i++)
  {
    ptr +=4;
  }

i woke up this morning and had an idea but im not sure it will work.  what if i did something like this:

char text1[3];
  for(int i=10, j=0; i<13; i++, j++)
  {
    textCopy[j] = textBuff;
  }

char text2[3];
  for(int i=14, j=0; i<17; i++, j++)
  {
    textCopy[j] = textBuff;
  }

char text3[3];
  for(int i=18, j=0; i<21; i++, j++)
  {
    textCopy[j] = textBuff;
  }

char text4[3];
  for(int i=22, j=0; i<25; i++, j++)
  {
    text4[j] = textBuff;
  }

would that copy the 3 values into one new value?  now giving me 4 (3 digit) values?

thanks

[Reply #9 on:]

Code:

char *ptr = textCopy[0];

Remove the

• from this line.

Code:

for(int i=0; i<4; i++)
 {
   ptr +=4;
 }

This block is missing the call to atoi() and the storage of the return value in the octet array.

[Reply #10 on:]

it all works wonderfully now...thank you so much for all of your help.   these forums are so great!!!!