nrf52 DK try to set duty to 0 but i still could get about 400mv of LED

[Justin]

Dears:

I try to use nRF52_SDK_0.9.0_0c82e3e SDK pheripheral pwm example and set the channel1(led2)

duty to 0.

But i still could get the signal about 400mv with LED2(P0.18).

Would that be normal??

In my opinion it should 0v when i set the duty to 0.

Would i miss anything??

Please correct me if i am wrong.

Thanks for your command.

[Stefan Birnir Sverrisson]

Hi Justin

On my side, when testing this with nRF52-DK preview board (PCA10036), pwm example from nRF52 SDK 0.9.2, the voltage is 0.0V on both pin P0.17 and P0.18 when I set the duty cycle as follows:

int main(void)
{
		ret_code_t err_code;
		
		/* 2-channel PWM, 200Hz, output on DK LED pins. */
		app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_2CH(5000L, BSP_LED_0, BSP_LED_1);
		
		/* Switch the polarity of the second channel. */
		pwm1_cfg.pin_polarity[1] = APP_PWM_POLARITY_ACTIVE_HIGH;
		
		/* Initialize and enable PWM. */
		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, 0);
		app_pwm_channel_duty_set(&PWM1, 1, 100);
	
		uint32_t value;
		while(true)
		{
		} 
}

[Justin]

Dear Stefan:

Thanks for your quickly reply. I try to use nRF52 SDK 0.9.2 and use the example as above on my DK(PCA10040). And I still could get the 400mv on BSP_LED_1 and 2.87v on the BSP_LED_0. As i know if we set the pin to Active_high. Set duty to 0 it should reply 0v and set duty to 100 will reply 2.87v. If we set the pin Active low. Set duty to 0 it should reply 2.87v and set duty to 100 will reply 0v. If i am wrong please correct me. I try to just config one channel PWM. The result is the same. It looked like i coulne't set the pin to 0v. Would you please give some command or hint?? Thanks a lot.