typedef struct {

  uint8_t startSymbol;
  uint8_t packetType;
  uint32_t deviceId;
  uint16_t packetCRC;

} PacketData __attribute__((packed));

typedef struct {
    int a;
    char c;
} mystruct __attribute__((packed));

typedef struct __attribute__((packed)) {
    int a;
    char c;
} mystruct;