关于MWC四轴代码读写EEPROM的问题

WZY008

最近在研究WMC代码时发现，在MWC的2.2版本代码中读写EEPROM时用到以下函数，像是较验用的，但具体还是不很明白，希望能够得到高人的指点，先谢过了！

uint8_t calculate_sum(uint8_t *cb , uint8_t siz)
{
  uint8_t sum=0x55;  // checksum init
  while(--siz) sum += *cb++;  // calculate checksum (without checksum byte)
  return sum;
}

上面这个函数在读EEPROM的函数中调用了，不知道具体做什么用

void readEEPROM() {
  uint8_t i;
  #ifdef MULTIPLE_CONFIGURATION_PROFILES
    if(global_conf.currentSet>2) global_conf.currentSet=0;
  #else
    global_conf.currentSet=0;
  #endif
  eeprom_read_block((void*)&conf, (void*)(global_conf.currentSet * sizeof(conf) + sizeof(global_conf)), sizeof(conf));
  if(calculate_sum((uint8_t*)&conf, sizeof(conf)) != conf.checksum) {
    blinkLED(6,100,3);   
    #if defined(BUZZER)
      alarmArray[7] = 3;
    #endif
    LoadDefaults();                 // force load defaults
  }
  for(i=0;i<6;i++) {
    lookupPitchRollRC[i] = (2500+conf.rcExpo8*(i*i-25))*i*(int32_t)conf.rcRate8/2500;
  }
  for(i=0;i<11;i++) {
    int16_t tmp = 10*i-conf.thrMid8;
    uint8_t y = 1;
    if (tmp>0) y = 100-conf.thrMid8;
    if (tmp<0) y = conf.thrMid8;
    lookupThrottleRC[i] = 10*conf.thrMid8 + tmp*( 100-conf.thrExpo8+(int32_t)conf.thrExpo8*(tmp*tmp)/(y*y) )/10; // [0;1000]
    lookupThrottleRC[i] = conf.minthrottle + (int32_t)(MAXTHROTTLE-conf.minthrottle)* lookupThrottleRC[i]/1000;            // [0;1000] -> [conf.minthrottle;MAXTHROTTLE]
  }

  #if defined(POWERMETER)
    pAlarm = (uint32_t) conf.powerTrigger1 * (uint32_t) PLEVELSCALE * (uint32_t) conf.pleveldiv; // need to cast before multiplying
  #endif
  #ifdef FLYING_WING
    #ifdef LCD_CONF
      conf.wing_left_mid  = constrain(conf.wing_left_mid, WING_LEFT_MIN,  WING_LEFT_MAX); //LEFT
      conf.wing_right_mid = constrain(conf.wing_right_mid, WING_RIGHT_MIN, WING_RIGHT_MAX); //RIGHT
    #else // w.o LCD support user may not find this value stored in eeprom, so always use the define value
      conf.wing_left_mid  = WING_LEFT_MID;
      conf.wing_right_mid = WING_RIGHT_MID;
    #endif
  #endif
  #ifdef TRI
    #ifdef LCD_CONF
      conf.tri_yaw_middle = constrain(conf.tri_yaw_middle, TRI_YAW_CONSTRAINT_MIN, TRI_YAW_CONSTRAINT_MAX); //REAR
    #else // w.o LCD support user may not find this value stored in eeprom, so always use the define value
      conf.tri_yaw_middle = TRI_YAW_MIDDLE;
    #endif
  #endif
  #if GPS
    if (f.I2C_INIT_DONE) GPS_set_pids();
  #endif
  #ifdef POWERMETER_HARD
    conf.pleveldivsoft = PLEVELDIVSOFT;
  #endif
  #ifdef POWERMETER_SOFT
     conf.pleveldivsoft = conf.pleveldiv;
  #endif
  #if defined(ARMEDTIMEWARNING)
    ArmedTimeWarningMicroSeconds = (conf.armedtimewarning *1000000);
  #endif
}