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I was wondering if you guys could help me solve an arduino Coding problem. I've simplified the code to highlight the issue that I'm having. I've created a program to read streaming serial data to an array. This array needs to be printed at a specific time interval, delays in this case are insufficient, and I have resorted to using timer.h which can be found here http://playground.arduino.cc/Code/Timer . My intention was to read to an array of size index, and increment index. When index becomes a value of 80, it is supposed to save the the array (inData) to another array("prntfd"). ("prntfd") is printed every 5 seconds. In this I hoped to decouple the serial timing, and the print timing of a serial data array.

Unfortunately the code only prints "c", and a print line. The code is below. Any insights would be much appreciated

    //Sketch feeds serial data to array (inData) of size (index). 
//A timer library is then used to print the data every 5 seconds
//debugs: a,b,c are inserted at various parts of the code.
//Serial data from inChar should print every 5 seconds just after C.

//Include timer libraries and serial library
#include <Event.h>
#include <Timer.h>
#include <NewSoftSerial.h>

//set serial pins, serial feed array "inData" and its index "index"
NewSoftSerial nss(3,4);
Timer t;
char inData[80];
static char prntfd[80];
int index = 0;

void setup()
  t.every(5000, takeReading);//set call time to function "take reading"

void loop()


  char inChar = nss.read();
  if (index <(80))
    inData[index++] = inChar;
    inData[index] = '\0';
  else if (index == 80)
  inData == prntfd;
  index = 0;
void takeReading()

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Helping fix your code is off-topic here. –  Winston Ewert Feb 7 '13 at 22:21
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closed as off topic by Glenn Rogers, Jeff Vanzella, svick, palacsint, Yuushi Feb 7 '13 at 1:38

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1 Answer

The error is in

inData == prntfd;

First, "==" is a test not an assignment. Hence prntfd is not being updated. Secondly, it is backwards Thirdly, inData and prntfd are char arrays, not a type of "String" where "=" only works on String and not char array.

For char arrays you need to copy blocks of memory with something like the following command using the avrlibc's char * strcpy ( char * dest, const char * src )

strcpy(prntfd, inData);
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The answer provided contained a link which has complete descriptions: > The strncpy() function is similar to strcpy(), except that not more than n bytes of src are copied. Thus, if there is no null byte among the first n bytes of src, the result will not be null-terminated. > > In the case where the length of src is less than that of n, the remainder of dest will be padded with nulls. –  mpflaga Feb 7 '13 at 14:17
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