在Arduino上使用PROGMEM中结构函数指针

Question

我试图从存储在PROGMEM中的结构中读取一个函数指针，然后将一个值(输入)传递给相应的函数并保存返回的值，但是我找不到正确的语法。

uint8_t (*pStateFunc) (uint8_t);
uint8_t input; 
uint8_t nextstate;

enum MENUSTATES {STATE1, STATE2};

typedef struct PROGMEM {
  unsigned char state;
  uint16_t someNumber;   // Just arbitrary information
  uint8_t (*pFunc) (uint8_t input);
} MENU_STATE;

const MENU_STATE menu_state[] PROGMEM = {
  //  state  someNumber  pFunc
  {STATE1,   2,          NULL}, 
  {STATE2,   4,          doSomething},
  {0,        0,          NULL}
  };


// Get the Function 
pStateFunc = (PGM_VOID_P) pgm_read_byte(&menu_state[1].pFunc); 

// Execute the Function and save the returned state
nextstate = pStateFunc(input);

// Function Definition
uint8_t doSomething(u8int_t input){
    return STATE1;
}

我得到的只是来自Arduino IDE 1.6.5的以下错误：

invalid conversion from 'const void*' to 'uint8_t (*)(uint8_t) {aka unsigned char (*)(unsigned char)}' [-fpermissive]

如何从PROGMEM读取函数并正确执行？

Answer 1

你似乎只读了一个字节--我认为pgm_read_ptr会更合适。你需要把它转换成正确的类型：

typedef uint8_t (*StateFunc) (uint8_t);
pStateFunc = (StateFunc) pgm_read_ptr(&menu_state[1].pFunc);