Using Optimisation in nrf51 Keil

[nordicdev]

Hi, I have the following piece of code.

nrf_gpio_cfg_output(PIN_EN_BSTR);

for(int i=0;i<300;i++)

{

	nrf_gpio_pin_clear(PIN_EN_BSTR);

	__NOP();

	__NOP();

	__NOP();

	__NOP();

	__NOP();

	__NOP();

	__NOP();

	__NOP();

	__NOP();

	__NOP();	

	nrf_gpio_pin_set(PIN_EN_BSTR);

	nrf_delay_us(100);

}

nrf_gpio_pin_clear(PIN_EN_BSTR);

With Optimisation level O0, the off time is 2usec and with O3, the off time is 1.4usec. Will __NOPs have different cycle time for different optimisation levels? I thought they should be the same? Thanks.

[nordicdev]

Hi Aryan, Thanks for your reply. With O0, even without adding any nops(whether inline or not), there is a delay of 1usec between nrf_gpio_pin_clear and nrf_gpio_pin_set. With O3, there is 320nsec between nrf_gpio_pin_clear and nrf_gpio_pin_set. So, if I add nops(inline or not), this is further going to add delay in the O0. I want the delay to be the same irrespective whether it is O0 or O3. Is it possible? Thanks. THis is my code:

nrf_gpio_cfg_output(PIN_EN_BSTR);

for(int i=0;i<300;i++)

{

	nrf_gpio_pin_clear(PIN_EN_BSTR);


	nrf_gpio_pin_set(PIN_EN_BSTR);

	nrf_delay_us(100);

}

nrf_gpio_pin_clear(PIN_EN_BSTR);