How to call a function from another "C" file

Projects Programming
1

Hello,
i have a sketch which is using some c files for a lvgl gui.
I would like to call a function which is located in the ino from one of these files.
But i always got the error message undefined reference to that function.
i tried a few things but none of them worked.

any idea ?

2

Post code?
Post error messages?
Use the "extern" keyword?

3

Error message
C:\Users...\events_init.c:234: undefined reference to `set_led_brightness'
collect2.exe: error: ld returned 1 exit status

exit status 1

Compilation error: exit status 1

I have the test funtion set_led_brightness

in the c file is use: extern void set_led_brightness (uint8_t val);
and the function call. set_led_brightness (VAL);

the function is located in my ino file:
void set_led_brightness (uint8_t val)
{
Serial.print("new brightness val:");
Serial.print("val");
Serial.print("\n\r");
}

4

in this case, the problem is that a function in a .cpp/.ino file is being called from a .c file. rename it events_init.cpp

5

ok i understand, the problem is that this file is auto generated and a lot of other files have now a problem to work with it.

6

say the function in the .ino file that you want to be visible is call foo

int foo(int someParam) {
  // do some stuff here
}

then surround it with this

extern "C" { // <=== ADD THIS
  int foo(int someParam) {
    // do some stuff here
  }
} // <=== AND CLOSE IT AFTER THE FUNCTION

then at the top of your c file do

extern int foo(int);

that should do the trick

an example in wokwi

7

not working. i did exacly the same like on the simulator
error: conflicting declaration of 'void setup()' with 'C' linkage
void setup()

8

Did you put setup() as C ?

9

no its a standard ino file

10

Why make us play guessing games? Post your complete code. Use Code Tags!

12

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