Ejemplo, define y asigna valores:
UINT8 hexRec2[5] = {0xA5, 0x41, 0x7B, 0xC7, 0x2F};
Puedes usar los tipos de campo estandar de C, o crear los tuyos propios como en el ejemplo (almacenados en GenerycTypeDefs.h):
typedef signed int INT;
typedef signed char INT8;
typedef signed short int INT16;
typedef signed long int INT32;
typedef signed long long INT64;
typedef unsigned int UINT;
typedef unsigned char UINT8;
typedef unsigned short int UINT16;
typedef unsigned long int UINT32; // other name for 32-bit integer
typedef unsigned long long UINT64;