Controlling port pins

RE: Controlling port pins

2R — Sat, 08 Aug 2015 20:26:46 GMT

Am I correct to say, OUTCLR by 1 has no effect, but OUTCLR by 0 will clear the pin?

RE: Controlling port pins

Stefan Birnir Sverrisson — Tue, 16 Dec 2014 12:12:18 GMT

Yes, I recommend to use the nrf_gpio library

RE: Controlling port pins

Julian — Mon, 15 Dec 2014 15:31:57 GMT

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

RE: Controlling port pins

John — Mon, 15 Dec 2014 15:15:55 GMT

Yes, that is correct. If you do a NRF_GPIO->OUTSET = 23; you are setting the output states for the entire port, not GPIO pin 23. That is why the nrf_gpio_pin_set shifts a 1 bit by the pin number you pass in to set the pin as an output. I'd suggest reading the GPIO section of the reference manual (Section 14 in revision 3.0). Note that setting a OUTSET bit to a zero has no effect which is why that assignment doesn't need to be an |=

RE: Controlling port pins

Stefan Birnir Sverrisson — Mon, 15 Dec 2014 15:00:27 GMT

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.

RE: Controlling port pins

Julian — Sun, 14 Dec 2014 23:38:38 GMT

Interesting point: - the binary value for 23 (17 HEX) is .....00010111 --- which would suggest that NRF_GPIO->Outset(pin_number) is setting the port, not an individual pin - although the attached comment in file nrf_gpio.h would suggest otherwise. The code was taken from the spi_master_example project.