I am currently gathering info from a BLE device. I made a thread earlier where I successfully split a string consisting of 5 letters to their unique chars.

However from this BLE device i will also send some different information from time to time where I send 3 different values with a space after each one. So for example looking like this:

-0.1 0.51 0.07

So what I want to do now is to store this three numbers in different doubles and what I have done so far is this:

First i store the recieved message:

String recievedMessage;

recievedMessage += (char)BTLEserial.read();

Now I have to determine if the value sent is the 5 letters or if it is the numbers with a space between each value.

if (recievedMessage.length() > 5) //so if the recievedmessage is more than 5 words then it is the 3 values that is being sent.
char * charTheMessage = recievedMessage.c_str();
char *str;
str = strtok(charTheMessage, " ");

double one = str[0];
double two = str[1];
double three = str[2];

Serial.println (one);
Serial.println (two);
Serial.println (three);


if (recievedMessage.length() == 5)
//Here I split the letters into 5 different values if the value sent is 5. 

But this values do not come out right when I print them in the serial monitor. I have also read that strtok is not reliable when data is sent fast so is strtok the right way to go you think?

1 Answer 1


You're almost there. Strtok returns the first token in the string only. You then have to convert that to a double yourself. You then call strtok again with NULL as the source string to get the next token. And so on.

I have written a good strtok example on here already. Look around, you may find it.

  • I am out and about and using my phone right now so can't do a complex answer.
    – Majenko
    Mar 27, 2017 at 9:53
  • Here is one example: arduino.stackexchange.com/questions/31126/…
    – Majenko
    Mar 27, 2017 at 12:31
  • Trying it right now! :) Will strncmp also work with spaces?
    – Martman
    Mar 27, 2017 at 12:50
  • strncmp sees space as just another character
    – Majenko
    Mar 27, 2017 at 12:51
  • ok, let me try to see if i can work it out!
    – Martman
    Mar 27, 2017 at 12:54

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