Controlling port pins

[Julian]

I am trying to debug a SPI application using Keil and the Eval board, but am having problems with control of the port pins. I am using pin 23 as the CS pin. it configures correctly as an output, but the functions NRF_GPIO->OUTSET = 23; and NRF_GPIO->OUTCLR = 23; have no effect on GPIO pin 23. however these instructions cause GPIO pins 0, 1, 2 and 4 to be set/reset. These two functions are declared in nrf_gpio.h :-

static __INLINE void nrf_gpio_pin_set(uint32_t pin_number)

{

NRF_GPIO->OUTSET = (1UL << pin_number);

}

However, if I call the function nrf_gpio_pin_set(23); followed by nrf_gpio_pin_clear(23); in a loop the pin toggles as it should.

There also appears to be no activity on the other SPI pins - but one problem at a time !

[Stefan Birnir Sverrisson]

Hi

You observation is as expected. When you write NRF_GPIO->OUTSET = 23 you will set pin 0, 1, 2 and 4 since OUTSET is a 32 bit register and the decimal number 23 is equal to binary number 10111. However, when you call nrf_gpio_pin_set, the number 1 is shifted 23 places in the register and therefore pin 23 is set.

[Julian]

I was aware of what you describe, but I missed the significance of the arguments. I now realise that nrf_gpio_pin_set(23) has an argument that defines the pin number, whereas If I want to use NRF_GPIO->OUTSET I should have written NRF_GPIO->OUTSET= (1UL<<23). I think I will stick to nrf_gpio_pin_set