c understanding struct pointer -

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could explain line static volatile gpio_registers* const gpio[] in code below?

and syntax (volatile gpio_registers*) inside block do?

// gpio hardware registers // typedef struct {   uint32_t mode;   uint32_t type;   uint32_t speed;   uint32_t push_pull;   uint32_t idr;   uint32_t odr;   uint32_t bsrr;   uint32_t lock;   uint32_t alt_fn1;   uint32_t alt_fn2; } gpio_registers;   // ports can selected using enumeration // (port) index array. // port addresses can calculated using enum since // ports @ same offset each other. // static volatile gpio_registers* const gpio[] = {   (volatile gpio_registers*)(gpio_base_addr + (port_a << 10)),   (volatile gpio_registers*)(gpio_base_addr + (port_b << 10)),   (volatile gpio_registers*)(gpio_base_addr + (port_c << 10)),   (volatile gpio_registers*)(gpio_base_addr + (port_d << 10)),   (volatile gpio_registers*)(gpio_base_addr + (port_e << 10)),   (volatile gpio_registers*)(gpio_base_addr + (port_f << 10)) };

static volatile gpio_registers* const gpio[] static array of pointer gpio_registers variables.

each element of array point physical address of soc/mcu. each element points physical gpio port. take of soc/mcu datasheet details. you'll find out each gpio port of soc has 32bits registers specified gpio_registers struct.

(volatile gpio_registers*) simple type cast required due fact gpio_base_addr , other defines simple "numbers" , must specify type of "numbers".


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