Cant change registers via pionters on nrf53

[TiNy]

Hi, I want write code on rust, but build system of nrf sdk for nrf5340 too hard for creating bindings, so I decide to create own HAL on rust and embed it in C with BLE stack on C. I start write test code on C for blinking leds on nrf5340dk. When I write this code on C, it just dont work, but when I do the same steps on GDB, all work fine. I also noticed that when I write value at registers in code, all operations just ignore.

static void turn_on_all_leds()
{
    volatile uint32_t *gpio_base = (uint32_t *) 0x50842500UL;
    volatile uint32_t *gpio_out_clr = (uint32_t *) (gpio_base + 0x00CUL);
    volatile uint32_t *gpio_dir_set = (uint32_t *) (gpio_base + 0x018UL);

    *gpio_dir_set = 0xf0180000UL;
    *gpio_out_clr = 0x00180000UL;
}

I read Reference manual and think that SPU may prevent my work with registers, but I dont know, How I should turn off SPU correct or how I can setup sdk for it, or may be my problem related to something else. When I try get some information about setup SPU at GDB, it tell that it cant access memory. How I can work with all registers whenever I want?

[Carl Richard]

Hello!

There already exists  some Rust crates for nRF53. I suggest trying out those. If you are facing issues with the crates or wonder about their usage please reach out to the Rust embedded working group as they probably can provide better help than us.

Best regards,
Carl Richard

[TiNy]

oh, I see, thanks for link, but I still confused whats exactly wrong with code above? Why when I setup registers via set command at gdb its work fine, but when i do same setup from C code in nrfconnect sdk, its not work?

[Carl Richard]

Which board are you targeting when building for the nRF Connect SDK?

Best regards,
Carl Richard

[TiNy]

nrf5340dk_nrf5340_cpuapp

[Carl Richard]

Interesting. The SPU should not affect anything unless you're building for nrf5340dk_nrf5340_cpuappns, but if that's not the case I need to do some more investigation.

Will get back to you over the weekend! Thank you for your patience.

Best regards,
Carl Richard

[TiNy]

Thanks for response. I'll wait you.

[Carl Richard]

Hello again!

Apologies for the delayed answer here. I reached out to some colleagues and they pointed out a mistake in your code. When you deal with pointer types the arithmetic take the pointer type into account. As an example, if you have a pointer to an array of uint32_t, and you want to access the next element in the array you have to increase the pointer by 4. In this case this means that your gpio_out_clr and gpio_dir_set pointers end up with the wrong value. This can be fixed by casting gpio_base to and int before doing the addition. Like this:

volatile uint32_t *gpio_base = (uint32_t *) 0x50842500UL;
volatile uint32_t *gpio_out_clr = (uint32_t *) ((int)gpio_base + 0x00CUL);
volatile uint32_t *gpio_dir_set = (uint32_t *) ((int)gpio_base + 0x018UL);

*gpio_dir_set = 0xf0180000UL;
*gpio_out_clr = 0x00180000UL;

By the way, one of the developers pointed out that you can use the standalone nRFX driver set as a starting point, instead of implementing your own HAL.

Best regards,
Carl Richard

[TiNy]

Thank for your answer and advice. It work exactly how you say.