使用指针直接访问寄存器

Question

我正在尝试使用指针直接访问 nrf52840 usb 加密狗中的寄存器。我正在使用 Segger Embedded Studio 编译和 link 所有内容，但它似乎生成了不正确的 RAM 和闪存位置。编辑 linker 文件并重新编译后，一切似乎都在正确的地方；然而，编程后（使用 NRF Connect 完成）LED 仍然不亮。我的想法是我可能错误地寻址了寄存器。谁能告诉我我是否正确使用指针？

注意：无法使用 Segger Embedded Studio 对 nrf52840 usb dongle 进行编程，因为 nrf52840 usb dongle 没有调试器。

LED_Test.c

// RGB LED at pins 22(G), 23(R), and 24(B)

// Addresses to registers, tasks, and events for the clock
#define CLOCK_BASE_ADDRESS     0x40000000
#define TASKS_HFCLKSTART_OFFSET     0x000
#define TASKS_LFCLKSTART_OFFSET     0x008
#define EVENTS_HFCLKSTARTED_OFFSET  0x100
#define EVENTS_LFCLKSTARTED_OFFSET  0x104
#define LFCLKSRC_ADDRESS_OFFSET     0x518

// Addresses to registers, tasks, and events for the GPIO
#define GPIO_BASE_ADDRESS      0x50000000
#define OUTSET_ADDRESS_OFFSET       0x508  //  1's written to this register set corresponding pins (HIGH). 0's have no effect.
#define DIRSET_ADDRESS_OFFSET       0x518  //  1's written to this register setup corresponding pins as OUTPUT. 0's have no effect.

volatile unsigned long * startHFClk_reg     = (volatile unsigned long *)CLOCK_BASE_ADDRESS  + TASKS_HFCLKSTART_OFFSET;
volatile unsigned long * HFClkStarted_reg   = (volatile unsigned long *)CLOCK_BASE_ADDRESS  + EVENTS_HFCLKSTARTED_OFFSET;
volatile unsigned long * LFClkSource_reg    = (volatile unsigned long *)CLOCK_BASE_ADDRESS  + LFCLKSRC_ADDRESS_OFFSET;
volatile unsigned long * startLFClk_reg     = (volatile unsigned long *)CLOCK_BASE_ADDRESS  + TASKS_LFCLKSTART_OFFSET;
volatile unsigned long * LFClkStarted_reg   = (volatile unsigned long *)CLOCK_BASE_ADDRESS  + EVENTS_LFCLKSTARTED_OFFSET;

volatile unsigned long * setupOutputs_reg   = (volatile unsigned long *)GPIO_BASE_ADDRESS   + DIRSET_ADDRESS_OFFSET;
volatile unsigned long * setPins_reg        = (volatile unsigned long *)GPIO_BASE_ADDRESS   + OUTSET_ADDRESS_OFFSET;

void main(void){

    *startHFClk_reg     = 0x01;         //  Start external 64 MHz crystal oscillator
    while(!HFClkStarted_reg){}
    *LFClkSource_reg    = 0x01;         //  LF oscillator source = external xtal
    *startLFClk_reg     = 0x01;         //  Start external 32.768 kHz crystal oscillator
    while(!LFClkStarted_reg){}

    *setupOutputs_reg   = 0x01C00000;   //  Make pins 22, 23, and 24 OUTPUT

    for(;;){
        *setPins_reg    = 0x00400000;   //  Make pin 22 HIGH
    }
}

Answer 1

您的寄存器的偏移量似乎是相对于您的基地址的字节偏移量。

然后你像这样创建你的指针：

volatile unsigned long * startHFClk_reg     = (volatile unsigned long *)CLOCK_BASE_ADDRESS  + TASKS_HFCLKSTART_OFFSET;

您从 CLOCK_BASE_ADDRESS 创建一个 volatile unsigned long *，然后添加偏移量。这里应用了指针算法的规则。您将 TASKS_HFCLKSTART_OFFSET * sizeof(unsigned long) 添加到基址。

要避免这种情况，请尝试

volatile unsigned long * startHFClk_reg     = (volatile unsigned long *)(CLOCK_BASE_ADDRESS  + TASKS_HFCLKSTART_OFFSET);

使用指针直接访问寄存器

Using pointers for direct register access

c

pointers

nrf52