#ifndef PWM_H
#define PWM_H

extern void PwmInit(uint8_t channel);
extern void PwmSetPeriod(uint8_t channel, uint32_t frequency);
extern void PwmSetDuty(uint8_t channel, uint8_t duty);


typedef struct
{
    uint32_t frequency;
    uint8_t duty;
} PwmOutput;

#endif //PWM_H

#ifndef PWM_H
#define PWM_H

void PwmInit(uint8_t channel);
void PwmSetPeriod(uint8_t channel, uint32_t frequency);
void PwmSetDuty(uint8_t channel, uint8_t duty);


typedef struct
{
    uint32_t frequency;
    uint8_t duty;
} PwmOutput;

#endif //PWM_H

--- 
+++ 
@@ -1,9 +1,9 @@
 #ifndef PWM_H
 #define PWM_H
 
-void PwmInit(uint8_t channel);
-void PwmSetPeriod(uint8_t channel, uint32_t frequency);
-void PwmSetDuty(uint8_t channel, uint8_t duty);
+extern void PwmInit(uint8_t channel);
+extern void PwmSetPeriod(uint8_t channel, uint32_t frequency);
+extern void PwmSetDuty(uint8_t channel, uint8_t duty);
 
 
 typedef struct
Update prototypes to make them more compliant.
