Serial com checksun receptor

const uint8_t header = 0x7E;
const uint8_t bufferSize = 4;
uint8_t buffer[bufferSize];
uint8_t readCounter;
uint8_t isHeader;
uint8_t firstTimeHeader;

int a=0;
int b=0;
void setup(){
Serial.begin(115200);
readCounter = 0;
isHeader = 0;
firstTimeHeader = 0;
}
void loop()
{
                     if(Serial.available() > 0){
                    uint8_t c = Serial.read();
                    if(c == header){
                       if(!firstTimeHeader){
                        isHeader = 1;
                        readCounter = 0;
                        firstTimeHeader = 1;
                      }
                    }
                    buffer[readCounter] = c;
                    readCounter++;

                    if(readCounter >= bufferSize){
                      readCounter = 0;

                      if(isHeader){

                        uint8_t checksumValue = buffer[3];

                        if(verifyChecksum(checksumValue)){
                          int a = (buffer[1]);
                           int b = (buffer[2]);
                        }
                        isHeader = 0;
                        firstTimeHeader = 0;
                      }
                    }
                  }




            }




uint8_t verifyChecksum(uint8_t originalResult){
  uint8_t result = 0;
  uint16_t sum = 0;

  for(uint8_t i = 0; i < (bufferSize - 1); i++){
    sum += buffer[i];
  }
  result = sum & 0xFF;

  if(originalResult == result){
     return 1;
  }else{
     return 0;
  }
}