如何在 Arduino 库中将十进制转换为十六进制

Question

I need to add a conversion from dec to hex in this function but failed.

    void AB1805::set_minute(const uint8_t value)
{
  _minute = value % MAX_MINUTE;
  write_rtc_register(MINUTE_REGISTER, _minute);
}

I tried

void AB1805::set_minute(const uint8_t value)
{
  _minute = value % MAX_MINUTE;
  write_rtc_register(MINUTE_REGISTER, dec_hex(_minute,2));
}

uint8_t AB1805::dec_hex(uint8_t tens, uint8_t digits)
{
  uint8_t ret;
  ret = (tens<<4) + digits;
  return ret;
}

Answer 1

Hexadecimal and decimal notation are just two different ways to express the same value.

set_minute(255); is the exact same thing as set_minute(0xFF); or set_minute(0b11111111);

You only need to specify a format if you want a string representation of that number in a specific format. Not if you want to just use that value in your code.

Answer 2

Typically, RTCs store the data in BCD format

uint8_t toBCD(uint8_t val) {  // expects a value 0 .. 99 
  return (val%10 & 0x0F) | (val/10 << 4); // returns 0x00 .. 0x99
}

No error checking, as usual in the Arduino world.