Pulsewidth modulation with app_pwm results in NRF_ERROR_INVALID_STATE

[stephbur]

I have a nrf51-DK. I am trying to get a PWM signal on one pin. Here is my code:

static volatile bool ready_flag;
void pwm_ready_callback(uint32_t pwm_id){ ready_flag = true; }      // PWM callback function

void test_pwm(){
    APP_PWM_INSTANCE(PWM1,2);                   // Create the instance "PWM1" using TIMER2.
    ret_code_t err_code;
    app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(5000L, 17);
    pwm1_cfg.pin_polarity[0] = APP_PWM_POLARITY_ACTIVE_HIGH;
    err_code = app_pwm_init(&PWM1,&pwm1_cfg,pwm_ready_callback);
    APP_ERROR_CHECK(err_code);
    app_pwm_enable(&PWM1);
    app_pwm_channel_duty_set(&PWM1, 0, 50);
}

The error code returned by init is 8 NRF_ERROR_INVALID_STATE. It happens with whatever TimerX (0,1,2) I use. I am not using a SoftDevice, nor am I using the Timers in another part of the code (except one SPI part, which is commented out atm).

What can I do to further debug the issue?

[Sigurd]

Hi,

The function app_pwm_init() will return NRF_ERROR_INVALID_STATE if the timer/PWM is already in use or if initialization failed. Are you calling the function app_pwm_init() more than once?

[Sigurd]

Could you post the code for the main() function ?

[stephbur]

the only thing I call in my main function is a setup function (which defines pins as input/output) and the function written above.

[stephbur]

I do not use any Timer nor a SoftDevice. It happens with TIMER0, TIMER1 and TIMER2. For some reason I cannot enable TIMER3/4 to test with them. I only call app_pwm_init() once. Defining the pin with nrf_gpio_cfg_output(17); should be alright, isn't it?

[Sigurd]

app_pwm_init takes care of initializing GPIOs, so you dont need to use the nrf_gpio_cfg_output.

nRF51 only have 3 TIMERS. nRF52832 have TIMER3 and TIMER4, but the nRF51 dont have them.

Could you upload your main.c here ?