diff --git a/driver/bk4819.c b/driver/bk4819.c
index 2f13dfd..7c6e05a 100644
--- a/driver/bk4819.c
+++ b/driver/bk4819.c
@@ -1930,22 +1930,26 @@ void BK4819_PlayRogerMDC1200(void)
 	uint16_t fsk_reg59;
 
 	#ifdef ENABLE_MDC1200
-		const uint8_t  op  = 0x12;
-		const uint8_t  arg = 0x34;
+		const uint8_t  op  = MDC1200_OP_CODE_POST_ID;
+		const uint8_t  arg = 0x00;
 		const uint16_t id  = 0x5678;
 
 		uint8_t packet[8 + 40];
 		memset(packet + 0, 0x00, 4);
 		memset(packet + 4, 0xff, 4);
-		const unsigned int size = MDC1200_encode_single_packet(packet + 8, op, arg, id);
+		const unsigned int size = 8 + MDC1200_encode_single_packet(packet + 8, op, arg, id);
 
 	#else
+		
 		static const uint8_t packet[] = {
 			0x00, 0x00, 0x00, 0x00,
 			0xff, 0xff, 0xff, 0xff,
 			// this needs properly computing for MDC1200
 			0xA2, 0xF1, 0x46, 0x74, 0xA4, 0x61, 0x44, 0x65, 0x8A, 0x4E, 0x44, 0xE0, 0x84, 0xEA
+		};
+		
 		const unsigned int size = sizeof(packet);
+		
 	};
 	#endif
 
diff --git a/firmware.bin b/firmware.bin
index 975e9f0..0ad8142 100644
Binary files a/firmware.bin and b/firmware.bin differ
diff --git a/firmware.packed.bin b/firmware.packed.bin
index 07e9fd9..203b668 100644
Binary files a/firmware.packed.bin and b/firmware.packed.bin differ
diff --git a/mdc1200.h b/mdc1200.h
index 3681193..2f2ebfb 100644
--- a/mdc1200.h
+++ b/mdc1200.h
@@ -4,6 +4,30 @@
 
 #include <stdint.h>
 
+// 0x01 (0x80) is PTT ID
+// 0x01 (0x00) is POST ID
+// 0x11 (0x8A) is REMOTE MONITOR
+// 0x22 (0x06) is STATUS REQ
+// 0x2B (0x0C) is RADIO ENABLE
+// 0x2B (0x00) is RADIO DISABLE
+// 0x35 (0x89) is CALL ALERT
+// 0x46 (0xXX) is STS XX
+// 0x47 (0xXX) is MSG XX
+// 0x63 (0x85) is RADIO CHECK
+
+enum mdc1200_op_code_e {
+	MDC1200_OP_CODE_PTT_ID         = 0x01,
+	MDC1200_OP_CODE_POST_ID        = 0x01,
+	MDC1200_OP_CODE_REMOTE_MONITOR = 0x11,
+	MDC1200_OP_CODE_STATUS_REQ     = 0x22,
+	MDC1200_OP_CODE_RADIO_ENABLE   = 0x2B,
+	MDC1200_OP_CODE_RADIO_DISABLE  = 0x2B,
+	MDC1200_OP_CODE_CALL_ALERT     = 0x35,
+	MDC1200_OP_CODE_STS_XX         = 0x46,
+	MDC1200_OP_CODE_MSG_XX         = 0x47,
+	MDC1200_OP_CODE_RADIO_CHECK    = 0x63
+};
+
 int MDC1200_encode_single_packet(uint8_t *data, const uint8_t op, const uint8_t arg, const uint16_t unit_id);
 int MDC1200_encode_double_packet(uint8_t *data, const uint8_t op, const uint8_t arg, const uint16_t unit_id, const uint8_t b0, const uint8_t b1, const uint8_t b2, const uint8_t b3);