Parsing multiple characters

Using Arduino Programming Questions
#1

I am trying to parse multiple characters using "," as a delimiter, but when i read serial data it takes each character one at a time, here is the code:

if(Serial.available()){
while(Serial.available()){
// clear the serial buffer
char sz = {Serial.read()};
char *str;
char *p = sz;
while ((str = strtok_r(p, ",", &p)) != NULL) // Don't use \n here it fails
{
Serial.println(str);
Serial.println("Location");
}}
while (Serial.available() > 0){ junk = Serial.read() ; }
}

it returns the below output when the input is (will,4,7)
w
Location
i
Location
l
Location
l
Location
4
Location
7
Location

Location

i want it to return
will
Location
4
Location
7

#2

strtok() operates on a string, not a char and the string ptr argument needs to be set to NULL on subsequent calls. for your case, the re-entrant version isn't needed.

consider the following code that produces the following with "1,2,3,4" as input and the serial monitor configured to terminate strings with \n

Location 1
Location 2
Location 3
Location 4

char s [80];
int  idx = 0;
void
loop ()
{
    if (Serial.available ()) {
        char  c = Serial.read ();
        s [idx++] = c;

        if ('\n' == c)  {
            s [idx-1] = '\0';
            idx = 0;

            char *str;
            char *p = s;

            for (p = s; (str = strtok (p, ",")); p = NULL) {
                Serial.print   ("Location ");
                Serial.println (str);
            }
        }
    }
}

void
setup ()
{
    Serial.begin (9600);
}
#3

i used the re-entrant version strtok_r

#4

i think it has something to do with serial reading one character at a time, but i'm not sure

#5

yes, you code reads one character at a time.
so your code needs to append each received character onto a string and once a complete string is received (i.e. terminated with \n), strtok() can process it.

#6

ok please stay online, i wanna check it out :slightly_smiling_face:

#7

actually i have this code that works but without a serial readout, can you please explain to me how it works, i don't really know much about these topics

#8

i just tried the code actually, but it isn't giving an output

#9 
#include "Arduino.h"
#include <SoftwareSerial.h>
SoftwareSerial BTserial(3, 2); // RX | TX  pinMode(RVPA,OUTPUT);
char junk;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
}

void loop() {
char s [80];
int  idx = 0;
    if (Serial.available ()) {
        char  c = Serial.read ();
        s [idx++] = c;

        if ('\n' == c)  {
            s [idx-1] = '\0';
            idx = 0;

            char *str;
            char *p = s;

            for (p = s; (str = strtok (p, ",")); p = NULL) {
                Serial.print   ("Location ");
                Serial.println (str);
            }
        }
    }
}

here's the full code i ran

#10

works on my Uno using the serial monitor. i see your doing something with SoftwareSerial.

in the code with "will,this,work", strtok() is passed a string.

in your original code, you read a single character from the serial port, read(), into a char variable, sz, (not a string). the code then invokes strtok() with a ptr to the single character and it does this for each character received from the serial interface. strtok() never see a string, just a char

#11

how can i convert the incoming serial to a string

#12

if i use Serial.readString(); i get a compilation error saying cannot convert 'String' to 'char' in initialization

#13

see reply #2

#14

String is not char s[]

#15 
if (Serial.available ()) {
        char  c = Serial.read ();
        s [idx++] = c;

        if ('\n' == c)  {
            s [idx-1] = '\0';
            idx = 0;

            char *str;
            char *p = s;

            for (p = s; (str = strtok (p, ",")); p = NULL) {
                Serial.print   ("Location ");
                Serial.println (str);
            }
        }
    }

thanks this code is now working on my Nano, i didn't set the serial monitor correctly and i also didn't use the char variables you stated earlier

#16

Although there is one small question i do not understand what you did with the for loop

#17

as you know, the first argument to strtok() is a ptr to the string to tokenize. the first part of the for initializes the ptr.

and as you know, strtok() should be called again as long as it returns a non-null value, the 2nd part of the for loop.

but that ptr should be set to null after the first call to strtok, and that's the 3rd part of the for loop. (obviously i've had to think about this before)