-volatile uint8_t recv_buf[32];
-uint8_t recv_head = 0;
-uint8_t recv_tail = 0;
-volatile uint8_t recv_fill = 0;
-volatile uint8_t recv_overrun = 0;
-uint8_t cmd_buf[15];
-uint8_t cmd_length;
-
-void process_commands(void);
-uint8_t process_command(void);