ESP8266 keeps crashing on sscanf()

Projects Programming
1

I am setting up 2 wemos D1 mini in a mesh. The connection and sending works, but reading the message keeps crashing on sscanf() and I can't tell why

void incommingMessage( uint32 from, String msg )
{
    uint16_t tokenState ;
    uint16_t tokenID ;
    char char_array[32];
    Serial.printf("echoNode: Received from %u msg=%s\n", from, msg.c_str());
    strcpy(char_array, msg.c_str());
    Serial.println("string copied to char array") ;
    Serial.println(char_array) ;
    sscanf( msg.c_str(), "%d,%d", &tokenID, &tokenState ) ; // <-- catastrophic failure
    Serial.println("array scanned") ;

    token[ tokenID ] = tokenState ; // update token with state
    printNumber_("token ", tokenID ) ;  // macro to print txt and number 
    printNumberln("= ",tokenState ) ;    // macro to print txt and number 
    
}

AFAIK I am doing it right. I use 16 bit variables for %d. And I did not forgot the &. The message also has the correct format. In this case 50,50

The output upon receiving is:

echoNode: Received from 2485300209 msg=50,50
string copied to char array
50,50

--------------- CUT HERE FOR EXCEPTION DECODER ---------------

Without sscanf(), the wemos does not crash.

Dit I do something wrong or am I looking at a bug?

Regards,

Bas

2

Quick glance. Shouldn't it be

    sscanf(char_array, "%d,%d", &tokenID, &tokenState ) ; // <-- catastrophic failure

?

3

I agree, but only because it would be clear to me. And I suggest doing it as a test anyway.

I don't use Strings, but shouldn't

   msg.c_str()

return a pointer to char?

a7

4 
sscanf( msg.c_str(), "%d,%d", &tokenID, &tokenState ) ;

%d scans a 4 byte integer, you need bigger targets, or a different format.
I think %hd is used for 16 bit entities.

https://en.cppreference.com/w/cpp/io/c/fscanf

6

I have been unclear.

This..

sscanf( msg.c_str(), "%d,%d", &tokenID, &tokenState ) ; // <-- catastrophic

and this

sscanf( char_array), "%d,%d", &tokenID, &tokenState ) ; // <-- catastrophic

I both tried. I started out with the char array as that is indeed the proper way like you point out. Later I changed it to msg.c_str() simply to see if it would make a change.

We got a winner though! (me because my wemos does not crash anymore).

Using uint32_t instead of uint16_t and using the char array seems to work. Apparently sscanf behaves differently with an 8 bit uController than on a Wemos. For an arduino Nano, I had to use 16 bit variables

The output:

echoNode: Received from 2485300209 msg=51,50
string copied to char array
51,50
array scanned  <--  Got a winner!
token 51 = 50

Now I just need me to change the printing so that 51 and 50 become 3 and 2 respectively. That I can do.

Tnx for the assist!

Regards,

Bas