+#define BAD_CRC 0x01
+#define SEQ_MISMATCH 0x02
+#define SHORT_ANSWER 0x03
+#define CMD_FAILED 0x04
+#define AUTH_FAILED 0x05
+#define READ_FAILED 0x06
+#define NO_PICC 0x07
+#define PICC_SELECT_ERROR 0x08
+
+/* gemtag commands */
+
+#define GEMTAG_CMD_PCD_CONFIG 0x10
+#define GEMTAG_CMD_PICC_ANTICOLL 0x12
+#define GEMTAG_CMD_PICC_SELECT 0x13
+
+#define GEMTAG_CMD_PICC_AUTH 0x14
+#define GEMTAG_CMD_PICC_AUTH_E2 0x15
+#define GEMTAG_CMD_HOST_CODE_KEY 0x16
+#define GEMTAG_CMD_PCD_LOAD_KEY_E2 0x17
+#define GEMTAG_CMD_PICC_AUTH_KEY 0x18
+#define GEMTAG_PICC_AUTHENT1A
+#define GEMTAG_PICC_AUTHENT1B
+
+#define GEMTAG_CMD_PICC_READ 0x19
+#define GEMTAG_CMD_PICC_WRITE 0x1a
+#define GEMTAG_CMD_PICC_VALUE 0x1b
+#define GEMTAG_CMD_PICC_VALUE_DEBIT 0x1c
+#define GEMTAG_CMD_PICC_HALT 0x1d
+#define GEMTAG_CMD_PICC_WRITE4 0x1e
+#define GEMTAG_CMD_COMMON_WRITE 0x1f
+#define GEMTAG_CMD_PCD_RF_RESET 0x20