user23056: I am a newbie to arduino programming. I wish to send big strings which are in range of 100 to 1000 characters to my arduino uno. I saw that arduino cannot read more than 63 characters at a time.

The strings can be received in parts (~40 characters) which will be processed by my program and few minutes later they will get deleted. Then another ~40 characters will be received and the process continues till all the characters are received.

Can you please help me with this. If the question is not clear, you're free to ask in the comments. Thanks in advance :-)

user4143: 
I saw that arduino cannot read more than 63 characters at a time.

Not strictly true. The Arduino core HardwareSerial library has a 64 byte buffer, so it can only buffer up to 64 characters. If your sketch is reading the characters from the buffer whilst you are sending the characters from your PC then that limit is irrelevant. As long as you are reading the characters as fast as they are coming in.
Serial is actually quite slow (on the scale of things) and unless you're doing silly things like using delay() or long blocking loops, then reading the data fast enough is not that big a problem.  If you do need more time the simplest way is just to slow down the serial data somewhat - i.e., use a lower baud rate. The slower you send the data the longer you get between each character arrives to do things.
For strings the size you are on about you are probably best off processing the data on the fly rather than storing it all then post-processing it - simply because the Arduino doesn't have much RAM, so storing large strings isn't always an option.

23056: <p>I am a newbie to arduino programming. I wish to send big strings which are in range of 100 to 1000 characters to my arduino uno. I saw that arduino cannot read more than 63 characters at a time.
<p>
The strings can be received in parts (~40 characters) which will be processed by my program and few minutes later they will get deleted. Then another ~40 characters will be received and the process continues till all the characters are received.
<p>
Can you please help me with this. If the question is not clear, you're free to ask in the comments. Thanks in advance :-)</p>
 4143: <blockquote>
  <p>I saw that arduino cannot read more than 63 characters at a time.</p>
</blockquote>

<p>Not strictly true. The Arduino core HardwareSerial library has a 64 byte buffer, so it can only <em>buffer</em> up to 64 characters. If your sketch is reading the characters from the buffer whilst you are sending the characters from your PC then that limit is irrelevant. As long as you are reading the characters as fast as they are coming in.</p>

<p>Serial is actually quite slow (on the scale of things) and unless you're doing silly things like using <code>delay()</code> or long blocking loops, then reading the data fast enough is not that big a problem.  If you do need more time the simplest way is just to slow down the serial data somewhat - i.e., use a lower baud rate. The slower you send the data the longer you get between each character arrives to do things.</p>

<p>For strings the size you are on about you are probably best off processing the data on the fly rather than storing it all then post-processing it - simply because the Arduino doesn't have much RAM, so storing large strings isn't always an option.</p>
