+#define XBEE_USER_RETCODE_OK 0
+#define XBEE_USER_RETCODE_BAD_FRAME 1
+#define XBEE_USER_RETCODE_TIMEOUT 2
+
+/* called when we receive an answer to a query */
+typedef int8_t (xbee_user_rx_cb_t)(int8_t code, void *frame,
+ unsigned len, void *arg);
+