Getting an undefined reference error for a defined function

Question

SDK 14.2, S140, NRF52840

I was trying to use the low_power_pwm library but upon copying the code from the lpp example, I get this:

Linking ble_bse_pca10056_s40.elf, 4 errors

"C:/Program Files/SEGGER/SEGGER Embedded Studio for ARM 4.30/gcc/arm-none-eabi/bin/ld" -X --omagic -eReset_Handler --defsym=__vfprintf=__vfprintf_long --defsym=__vfscanf=__vfscanf_int -EL --gc-sections "-TC:/<path to project folder>/Output/ble_bse_pca10056_s140 Debug/Obj/ble_bse_pca10056_s140.ld" -Map Output/Debug/Exe/ble_bse_pca10056_s140.map -u_vectors -o Output/Debug/Exe/ble_bse_pca10056_s140.elf --emit-relocs --start-group "@C:/<path to project folder>/Output/ble_bse_pca10056_s140 Debug/Obj/ble_bse_pca10056_s140.ind" --end-group

even though I have specified #include "low_power_pwm.h" at the top of the file. Any ideas why this is happening? All my other #includes work.

PWM code below, where LED_GREEN is the GPIO pin number for the green LED.

static low_power_pwm_t low_power_pwm_green;

/**
 * @brief Function to be called in timer interrupt.
 *
 * @param[in] p_context     General purpose pointer (unused).
 */
static void pwm_handler(void * p_context)
{
    uint8_t new_duty_cycle;
    static uint16_t led_0, led_1;
    uint32_t err_code;
    UNUSED_PARAMETER(p_context);

    low_power_pwm_t * pwm_instance = (low_power_pwm_t*)p_context;

	NRF_LOG_INFO("<in PWM handler>"); // placeholder to make sure function works
}

/**
 * @brief Function to initalize low_power_pwm instances.
 *
 */
static void pwm_init(void)
{
    uint32_t err_code;
    low_power_pwm_config_t low_power_pwm_config;

    APP_TIMER_DEF(pwm_timer_green);
    low_power_pwm_config.active_high    = false;
    low_power_pwm_config.period         = 220;
    low_power_pwm_config.bit_mask       = 1 << LED_GREEN;
    low_power_pwm_config.p_timer_id     = &pwm_timer_green;
    low_power_pwm_config.p_port         = NRF_GPIO;

    err_code = low_power_pwm_init((&low_power_pwm_green), &low_power_pwm_config, pwm_handler);
    APP_ERROR_CHECK(err_code);
    err_code = low_power_pwm_duty_set(&low_power_pwm_green, 20);
    APP_ERROR_CHECK(err_code);

    err_code = low_power_pwm_start((&low_power_pwm_green), low_power_pwm_green.bit_mask);
    APP_ERROR_CHECK(err_code);
}

pwm_init(); is called in main() after services_init(), advertising_init(), etc.

I have tried rebuilding the solution, cleaning & rebuilding the solution. Nothing solves the compilation error. The file low_power_pwm.h is unmodified. The error persists after I add the low_power_pwm.c file to the project via these instructions from Segger. I added it as an existing file, then I dragged it to the nrf_Libraries folder within the project.

nordev · Accepted Answer

Never mind, the issue was that #define LOW_POWER_PWM_ENABLED 
 was originally 0 and needed to be 1 in sdk_config

Getting an undefined reference error for a defined function

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