Sending an integer serially in Arduino

Question

I need to send an integer, say between 0-10000, to Arduino using serial communication. What's the best way of doing that?

I can think of breaking the number into an character array (eg: 500 as '5','0','0') and sending them as a byte stream (yeah, that's ugly). Then reconstruct at the other end. (anything is sent serially as a byte stream, right?)

Isn't there a better way? Somehow, it should be able to assign the value into an int type variable.

(really need to know the same thing about strings too, if possible)

score 9 · Accepted Answer · edited Feb 06 '21 at 18:40

If what you're looking for is speed, then instead of sending an ASCII encoded int, you can divide your number into two bytes, here's an example:

uint16_t number = 5703;               // 0001 0110 0100 0111
uint16_t mask   = B11111111;          // 0000 0000 1111 1111
uint8_t first_half   = number >> 8;   // >>>> >>>> 0001 0110
uint8_t sencond_half = number & mask; // ____ ____ 0100 0111
    
Serial.write(first_half);
Serial.write(sencond_half);

score 3 · Answer 2 · edited Dec 16 '12 at 20:31

3

You don't specify the from environment, so I assume your troubles is with reading serial data on an Arduino?

Anyways, as can be seen in the Arduino Serial reference, you can read an integer using the Serial.parseInt() method call. You can read strings with eg. Serial.readBytes(buffer, length) but your real issue is to know when to expect a string and when to expect an integer (and what to do if something else comes along, eg. noise or so...)

edited Dec 16 '12 at 20:31

Matthew Murdoch

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answered Dec 14 '12 at 10:00

Anders R. Bystrup

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Well, the _from_ environment can be considered as PC. But since it's serial communication that sender won't matter, eh? (Ultimately, i'm trying to use this in wireless communication, with [APC220](http://www.dfrobot.com/index.php?route=product/product&product_id=57#.UMsDR-TYfH8)). Anyway, thanks. Honestly, i wonder why i didn't see that before. I'll give a try. – Anubis Dec 14 '12 at 10:47

score 3 · Answer 3 · edited Feb 05 '21 at 23:41

3

Another way:

unsigned int number = 0x4142; //ASCII characters 'AB';
char *p;
    
p = (char*) &number;
    
Serial.write(p,2);

will return 'BA' on the console (LSB first).

edited Feb 05 '21 at 23:41

kabr8

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answered Nov 27 '14 at 21:12

Dave

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score 1 · Answer 4 · edited Feb 06 '21 at 19:59

1

Other way:

char p[2];
*p = 0x4142; //ASCII characters 'AB'
Serial.write(p,2);

I like this way.

edited Feb 06 '21 at 19:59

kabr8

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answered May 04 '16 at 22:02

Reynel Fals de Pedro

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score 0 · Answer 5 · edited Feb 06 '21 at 19:16

I am not from coding background, today i was trying the same and got it working.. I am just sending the number byte wise with start and end bytes added ('a' and 'b'). hope it helps..enter code here

//sending end
unsigned char a,n[4],b;
int mynum=1023;// the integer i am sending
for(i=0;i<4;i++)
{
    n[i]='0'+mynum%10; // extract digit and store it as char
    mynum=mynum/10;
}

SendByteSerially(a);
_delay_ms(5);
SendByteSerially(n[3]);
_delay_ms(5);
SendByteSerially(n[2]);
_delay_ms(5);
SendByteSerially(n[1]);
_delay_ms(5);
SendByteSerially(n[0]);
_delay_ms(5);
SendByteSerially(b);
_delay_ms(100);


//at receiving end. 
while(portOne.available() > 0) 
{
    char inByte = portOne.read();
    if(inByte!='a' && inByte !='b')
    {
    Serial.print(inByte);
    }
    else if(inByte ='a')
        Serial.println();
    else if(inByte ='b')
        Serial.flush();
    }
delay(100);

This is exactly what the OP describes as 'ugly' and wants to avoid. — Jan Doggen, Jan 29 '15 at 16:23

Sending an integer serially in Arduino

5 Answers5