Global variables are not updated

[masterLee]

Hi, I have created a global variables header file that I use through out my project. The variables are static volatile and intialized to zero.

When I update them with a new value (i.e. a =150) and try to print them to serial console of Segger, in main(), the printed values are all zero.

If I update them and print them in a function, located in another source file of the project , the variables are updated correctly.

I attach the header file code here in case you see something that I don't

#ifndef GLOBAL_VARIABLES_H
#define GLOBAL_VARIABLES_H

#ifdef __cplusplus
extern "C" {
#endif

#include "nrf_drv_twi.h"
#include "app_error.h"
#include "ICM20948.h"      

#define TWI_INSTANCE_ID     0
static const nrf_drv_twi_t m_twi = NRF_DRV_TWI_INSTANCE(TWI_INSTANCE_ID);

static volatile bool m_xfer_done = false;
static volatile ret_code_t err_code;
static volatile bool flag = false;

static volatile int16_t accel_X = 0;
static volatile int16_t accel_Y = 0;
static volatile int16_t accel_Z = 0;

static volatile int16_t gyro_X = 0;
static volatile int16_t gyro_Y = 0;
static volatile int16_t gyro_Z = 0;


static volatile uint16_t testVariable = 0;

#ifdef __cplusplus
}
#endif

#endif // GLOBAL_VARIABLES_H

Thank you

[Andy]

I'm no absolute expert in C, but I've worked with it for years already and I've never seen something like this. Does it even compile? Do you have warnings?

You should declare your variables in the header file and define them in the source file. You can't have them static and want them to be public at the same time. Also declaring everything as volatile is bad practice.

I'd advise you to read some C basics. There are tons of threads in stack overflow where you can start. For example: stackoverflow.com/.../variable-declaration-in-a-header-file

[hmolesworth]

Since this is a .h file you are defining a unique instance of these variables for every time the header file is included. As they are "static" each of these instances is not visible to any other module, but each is visible withiin that c file which included the .h file; remove "static" and you will see a flood of errors about multiple definitions. So to use them as global variables place them in a single c or cpp file and delete the "static" prefix; also keep the variables in the .h file, but replace "static" with "extern" which tells each c file that these variables are indeed global.

[masterLee]

No errors and no warnings are returned in segger. I use the same approach in MPLAB X IDE for PIC32 and values are updated with no problem..