[SOLVED] I2CMaster Lib undefined reference

Projects Programming
1

Hi,

I am using an Arduino Nano.

I have just installed I2CMaster from Peter Fleury : http://homepage.hispeed.ch/peterfleury/i2cmaster.zip

I managed to install it properly (https://forum.arduino.cc/index.php?topic=571741.0) but when I use a function from this lib I have the "undefined reference" to every functions I use.

ex:

#include <i2cmaster.h>

void setup() {
  Serial.begin(115200);
  i2c_init();
  while (!Serial);
  //PORTC = (1 << PORTC4) | (1 << PORTC5); //enable pullups
  Serial.print("BattMon 1.0 ");
  //i2c_stop();
}

void loop() {
 
}

Error :

C:\Users\tagadac\AppData\Local\Temp\ccOy0OiH.ltrans0.ltrans.o: In function `setup':

c:\Users\tagadac\Documents\Arduino\BQ2060Av1/BQ2060Av1.ino:5: undefined reference to `i2c_init()'

collect2.exe: error: ld returned 1 exit status

exit status 1
[Error] Exit with code=1

It's pretty confusing... I tried to rename "twimaster.c" to "i2cmaster.c" but (obviously) same error.

Thank you for your help.

2

I believe the correct form is using capital letters.

I2C_Init();

Here you can find some information about your library. Good luck!

3

Due to the file extension of twimaster.c, this code is compiled as C. But the Arduino IDE's .ino sketch files are actually compiled as C++, after some minor preprocessing (mostly just generating function prototypes). so you must wrap the #include directive in extern "C" {}:

extern "C" {
#include <i2cmaster.h>
}

void setup() {
  Serial.begin(115200);
  i2c_init();
  while (!Serial);
  //PORTC = (1 << PORTC4) | (1 << PORTC5); //enable pullups
  Serial.print("BattMon 1.0 ");
  //i2c_stop();
}

void loop() {
 
}
4

Thank you for your help.

pati130013:
I believe the correct form is using capital letters.

No it's not in capital letters, see doc here.

pert:
Due to the file extension of twimaster.c, this code is compiled as C. But the Arduino IDE's .ino sketch files are actually compiled as C++, after some minor preprocessing (mostly just generating function prototypes). so you must wrap the #include directive in extern "C" {}:

extern "C" {

#include <i2cmaster.h>
}

void setup() {
  Serial.begin(115200);
  i2c_init();
  while (!Serial);
  //PORTC = (1 << PORTC4) | (1 << PORTC5); //enable pullups
  Serial.print("BattMon 1.0 ");
  //i2c_stop();
}

void loop() {

}

Puuuuurrrrrrfect ! This works like a charm ! I did not know this was possible with includes.

Thank you !

5

I'm glad to hear it's working now.

Perhaps the best practice would be for the library's header file to be wrapped in:

#ifdef __cplusplus
extern "C" {
#endif

// C code here

#ifdef __cplusplus
}
#endif

but wrapping the #include directive accomplishes the same thing, without needing to modify the library files at all.

Enjoy!
Per