Question

I’m having trouble passing a struct into a function and I am running into an error:

‘PWM_PINS’ undeclared (first use in this function)

I am typically able to do this in a C++ compiler without any trouble. I would appreciate some advice as to what I might be doing wrong here.

I have included the relevant parts from the header and c file below.

pwm.h file:

typedef struct PWM_tag{
    int PWM_1;
    int PWM_2;
    int PWM_3;
    int PWM_4;
    int PWM_5;
    int PWM_6;
} PWM;

void PWM_Set( uint32_t channelNum, uint32_t cycle, PWM PWN_PINS );

pwm.c file:

#include "pwm.h"
 void PWM_Set( uint32_t ChannelNum, uint32_t cycle, PWM PWN_PINS)
    {
        if ( ChannelNum == 1 )
        {
            LPC_PWM1->MR0 = cycle;
            LPC_PWM1->MR1 = PWM_PINS.PWM_1;
            LPC_PWM1->MR2 = PWM_PINS.PWM_2;
            LPC_PWM1->MR3 = PWN_PINS.PWM_3;
            LPC_PWM1->MR4 = PWM_PINS.PWM_4;
            LPC_PWM1->MR5 = PWM_PINS.PWM_5;
            LPC_PWM1->MR6 = PWM_PINS.PWM_6;

        }
        return;
    }

Answer 1

You declared a parameter called PWN_PINS (with an N), but you are referring to PWM_PINS (with an M).

Fixing this typo will address this particular error. There may be more errors, though – it’s hard to tell, because the snippet does not show essential parts, such as the declaration of LPC_PWM1 variable.