diff --git a/Makefile b/Makefile
index b55843e..439a648 100644
--- a/Makefile
+++ b/Makefile
@@ -12,16 +12,16 @@ ENABLE_OVERLAY                   := 0
 ENABLE_LTO                       := 1
 # UART Programming 2.9 kB
 ENABLE_UART                      := 1
-ENABLE_UART_DEBUG                := 0
+ENABLE_UART_DEBUG                := 1
 # AirCopy 2.5 kB
-ENABLE_AIRCOPY                   := 0
+ENABLE_AIRCOPY                   := 1
 ENABLE_AIRCOPY_REMEMBER_FREQ     := 1
 ENABLE_AIRCOPY_RX_REBOOT         := 0
 # FM Radio 4.2 kB
 ENABLE_FMRADIO_76_90             := 0
 ENABLE_FMRADIO_68_108            := 0
 ENABLE_FMRADIO_76_108            := 0
-ENABLE_FMRADIO_875_108           := 1
+ENABLE_FMRADIO_875_108           := 0
 # NOAA 1.2 kB
 ENABLE_NOAA                      := 0
 # Voice 1.7 kB
@@ -33,7 +33,7 @@ ENABLE_REDUCE_LOW_MID_TX_POWER   := 1
 # Tx Alarm 0.6 kB
 ENABLE_ALARM                     := 0
 ENABLE_TX1750                    := 0
-# MDC1200 0.892 kB
+# MDC1200 2.8 kB
 ENABLE_MDC1200                   := 1
 ENABLE_PWRON_PASSWORD            := 0
 ENABLE_RESET_AES_KEY             := 1
@@ -66,7 +66,7 @@ ENABLE_SQ_OPEN_WITH_UP_DN_BUTTS  := 1
 ENABLE_FASTER_CHANNEL_SCAN       := 1
 ENABLE_COPY_CHAN_TO_VFO_TO_CHAN  := 1
 # Rx Signal Bar 0.4 kB
-ENABLE_RX_SIGNAL_BAR             := 1
+ENABLE_RX_SIGNAL_BAR             := 0
 # Tx Timeout Bar 0.2 kB
 ENABLE_TX_TIMEOUT_BAR            := 0
 # Tx Audio Bar 0.3 kB
diff --git a/am_fix.c b/am_fix.c
index 2683e75..e08f332 100644
--- a/am_fix.c
+++ b/am_fix.c
@@ -449,6 +449,9 @@
 
 		void AM_fix_print_data(const int vfo, char *s)
 		{
+			if (g_screen_to_display != DISPLAY_MAIN || g_dtmf_call_state != DTMF_CALL_STATE_NONE)
+				return;
+
 			if (s != NULL && vfo >= 0 && vfo < (int)ARRAY_SIZE(gain_table_index))
 			{
 				const unsigned int index = gain_table_index[vfo];
diff --git a/app/aircopy.c b/app/aircopy.c
index cf5e5e2..91cf0b6 100644
--- a/app/aircopy.c
+++ b/app/aircopy.c
@@ -393,27 +393,29 @@ void AIRCOPY_process_fsk_rx_10ms(void)
 		return;                                                // no flagged interrupts
 
 	// read the interrupt flags
-	BK4819_WriteRegister(0x02, 0);                    // clear them
+	BK4819_WriteRegister(0x02, 0);                             // clear them
 	interrupt_bits = BK4819_ReadRegister(0x02);
 
 	if (interrupt_bits & BK4819_REG_02_FSK_RX_SYNC)
-		BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, true);   // LED on
+		BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, true);    // LED on
 
 	if (interrupt_bits & BK4819_REG_02_FSK_RX_FINISHED)
-		BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, false);  // LED off
+		BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, false);   // LED off
 
 	if ((interrupt_bits & BK4819_REG_02_FSK_FIFO_ALMOST_FULL) == 0)
 		return;
 
-	BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, true);       // LED on
+	BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, true);        // LED on
 
-	// fetch RX'ed data
-	for (i = 0; i < 4; i++)
-	{
-		const uint16_t word = BK4819_ReadRegister(0x5F);
+	{	// fetch RX'ed data
+		const unsigned int count = BK4819_ReadRegister(0x5E) & (7u << 0); // almost full threshold
+		for (i = 0; i < count; i++)
+		{
+			const uint16_t word = BK4819_ReadRegister(0x5F);
 
-		if (g_fsk_write_index < ARRAY_SIZE(g_fsk_buffer))
-			g_fsk_buffer[g_fsk_write_index++] = word;
+			if (g_fsk_write_index < ARRAY_SIZE(g_fsk_buffer))
+				g_fsk_buffer[g_fsk_write_index++] = word;
+		}
 	}
 
 	// REG_0B read only
diff --git a/app/app.c b/app/app.c
index ab3a951..9ae7825 100644
--- a/app/app.c
+++ b/app/app.c
@@ -152,10 +152,19 @@ static void APP_check_for_new_receive(void)
 	g_rx_reception_mode = RX_MODE_DETECTED;
 
 done:
-	if (g_current_function != FUNCTION_NEW_RECEIVE)
+//	if (g_current_function != FUNCTION_NEW_RECEIVE)
 	{
 		FUNCTION_Select(FUNCTION_NEW_RECEIVE);
 
+		#ifdef ENABLE_MDC1200
+		{	// reset the FSK receiver
+			//const uint16_t fsk_reg59 = BK4819_ReadRegister(0x59) & ~((1u << 15) | (1u << 14) | (1u << 12) | (1u << 11));
+			//	BK4819_enable_mdc1200_rx(true);
+			//BK4819_WriteRegister(0x59, (1u << 15) | (1u << 14) | fsk_reg59);
+			//BK4819_WriteRegister(0x59, (1u << 12) | fsk_reg59);
+		}
+		#endif
+
 		APP_update_rssi(g_eeprom.rx_vfo);
 		g_update_rssi = true;
 	}
@@ -672,7 +681,7 @@ void APP_stop_scan(void)
 
 			g_rx_vfo->freq_config_rx.frequency = g_scan_restore_frequency;
 
-			RADIO_ApplyOffset(g_rx_vfo);
+			RADIO_ApplyOffset(g_rx_vfo, false);
 			RADIO_ConfigureSquelchAndOutputPower(g_rx_vfo);
 			RADIO_setup_registers(true);
 		}
@@ -684,7 +693,7 @@ void APP_stop_scan(void)
 
 		if (g_rx_vfo->channel_save > USER_CHANNEL_LAST)
 		{	// frequency mode
-			RADIO_ApplyOffset(g_rx_vfo);
+			RADIO_ApplyOffset(g_rx_vfo, false);
 			RADIO_ConfigureSquelchAndOutputPower(g_rx_vfo);
 			SETTINGS_save_channel(g_rx_vfo->channel_save, g_eeprom.rx_vfo, g_rx_vfo, 1);
 			return;
@@ -720,7 +729,7 @@ static void APP_next_freq(void)
 	if (new_band != old_band)
 	{	// original slow method
 
-		RADIO_ApplyOffset(g_rx_vfo);
+		RADIO_ApplyOffset(g_rx_vfo, false);
 		RADIO_ConfigureSquelchAndOutputPower(g_rx_vfo);
 		RADIO_setup_registers(true);
 
@@ -865,7 +874,7 @@ static void APP_next_channel(void)
 static void APP_toggle_dual_watch_vfo(void)
 {
 	#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-		UART_SendText("dual watch\r\n");
+		UART_SendText("dual wot\r\n");
 	#endif
 
 	#ifdef ENABLE_NOAA
@@ -907,7 +916,7 @@ void APP_process_radio_interrupts(void)
 	{	// BK chip interrupt request
 
 		uint16_t interrupt_bits;
-		
+
 		BK4819_WriteRegister(0x02, 0);
 		interrupt_bits = BK4819_ReadRegister(0x02);
 
@@ -1008,7 +1017,7 @@ void APP_process_radio_interrupts(void)
 			BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, false);  // LED off
 
 			#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-				UART_printf("squelch closed\r\n");
+				UART_SendText("sq close\r\n");
 			#endif
 		}
 
@@ -1017,130 +1026,12 @@ void APP_process_radio_interrupts(void)
 			g_squelch_open = true;
 
 			#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-				UART_printf("squelch opened\r\n");
+				UART_SendText("sq open\r\n");
 			#endif
 		}
 
 		#ifdef ENABLE_MDC1200
-		{
-			const uint16_t rx_sync_flags   = BK4819_ReadRegister(0x0B);
-			const uint16_t fsk_reg59       = BK4819_ReadRegister(0x59) & ~((1u << 15) | (1u << 14) | (1u << 12) | (1u << 11));
-
-			const bool rx_sync_neg         = (rx_sync_flags & (1u << 7)) ? true : false;
-			const bool rx_sync_pos         = (rx_sync_flags & (1u << 6)) ? true : false;
-			const bool rx_sync             = (interrupt_bits & BK4819_REG_02_FSK_RX_SYNC) ? true : false;
-			const bool rx_finished         = (interrupt_bits & BK4819_REG_02_FSK_RX_FINISHED) ? true : false;
-			const bool rx_fifo_almost_full = (interrupt_bits & BK4819_REG_02_FSK_FIFO_ALMOST_FULL) ? true : false;
-
-
-			BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, true);   // LED on
-
-			if (rx_sync_neg)
-			{	// RX sync neg found
-				#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-					UART_printf("fsk rx sync neg\r\n");
-				#endif
-			}
-
-			if (rx_sync_pos)
-			{	// RX sync pos found
-				#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-					UART_printf("fsk rx sync pos\r\n");
-				#endif
-			}
-
-			if (rx_sync)
-			{
-				#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-					UART_printf("fsk rx sync\r\n");
-				#endif
-			}
-
-			if (rx_fifo_almost_full)
-			{
-				uint8_t            buffer[sizeof(mdc1200_sync_suc_xor) + 14];
-				unsigned int       i;
-				uint8_t            op;
-				uint8_t            arg;
-				uint16_t           unit_id;
-
-				const unsigned int sync_size = (fsk_reg59 & (1u << 3)) ? 4 : 2; 
-//				const unsigned int size      = 1 + ((BK4819_ReadRegister(0x5D) >> 8) & 0xffff);
-				const unsigned int size      = sizeof(buffer) - sync_size;
-				
-				#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-					UART_printf("fsk rx almost full\r\n");
-				#endif
-
-				// 40 C4 B0 32 BA F9 33 18 35 08 83 F6 0C C9
-				// 0100000011000100101100000011001010111010111110010011001100011000001101010000100010000011111101100000110011001001
-
-				// 0100000011000100101100000011001010111010111110010011001100011000001101010000100010000011111101100000000011110101
-				// 1011111100111011010011111100110101000101000001101100110011100111110010101111011101111100000010011111111100001010
-
-				// BF 3B 4F CD 45 06 CC E7 CA F7 7C 09 FF 0A
-
-				{	// fetch RX'ed data .. 16-bits at a time
-
-					unsigned int k = 0;
-
-					// precede the data with the missing sync pattern
-					for (i = 0; i < sync_size; i++)
-						buffer[k++] = mdc1200_sync_suc_xor[i] ^ (rx_sync_neg ? 0x00 : 0xFF);
-
-					for (i = 0; i < (size / 2); i++)
-					{
-						const uint16_t word = BK4819_ReadRegister(0x5F);
-						buffer[k++] = (word >> 0) & 0xff;
-						buffer[k++] = (word >> 8) & 0xff;
-					}
-				}
-
-				// clear FIFO's then enable RX
-				BK4819_WriteRegister(0x59, (1u << 15) | (1u << 14) | fsk_reg59);
-				BK4819_WriteRegister(0x59, (1u << 12) | fsk_reg59);
-
-				#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-					UART_SendText("fsk rx ");
-					for (i = 0; i < sizeof(buffer); i++)
-						UART_printf(" %02X", buffer[i]);
-					UART_SendText("\r\n");
-				#endif
-
-				if (!g_squelch_open)
-					BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, false);  // LED off
-
-				if (MDC1200_process_rx(
-					buffer,
-					sizeof(buffer),
-//					(sync_flags & (1u << 7)) ? true : false, // true if the sync pattern is bit inverted
-					&op,
-					&arg,
-					&unit_id))
-				{
-					g_beep_to_play = BEEP_880HZ_60MS_TRIPLE_BEEP;
-
-					// TODO: display the packet
-
-
-					#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-						UART_printf("MDC1200  op %02X  arg %02X  id %04X\r\n", op, arg, unit_id);
-					#endif
-
-
-				}
-			}
-
-			if (rx_finished)
-			{
-				#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-					UART_printf("fsk rx finished\r\n");
-				#endif
-
-				BK4819_WriteRegister(0x59, (1u << 15) | (1u << 14) | fsk_reg59);
-				BK4819_WriteRegister(0x59, (1u << 12) | fsk_reg59);
-			}
-		}
+			MDC1200_process_rx(interrupt_bits);
 		#endif
 	}
 }
@@ -2234,6 +2125,13 @@ void APP_time_slice_500ms(void)
 		}
 	}
 
+	#ifdef ENABLE_MDC1200
+		if (mdc1200_rx_ready_tick_500ms > 0)
+			if (--mdc1200_rx_ready_tick_500ms == 0)
+				if (g_center_line == CENTER_LINE_MDC1200)
+					g_center_line = CENTER_LINE_NONE;
+	#endif
+
 	if (g_dtmf_rx_live_timeout > 0)
 	{
 		#ifdef ENABLE_RX_SIGNAL_BAR
@@ -2588,7 +2486,7 @@ void APP_channel_next(const bool remember_current, const scan_state_dir_t scan_d
 	}
 
 	#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-		UART_printf("APP_channel_next %u\r\n", g_scan_next_channel);
+//		UART_printf("APP_channel_next %u\r\n", g_scan_next_channel);
 	#endif
 
 	if (g_scan_next_channel <= USER_CHANNEL_LAST)
diff --git a/app/main.c b/app/main.c
index 0999468..183208e 100644
--- a/app/main.c
+++ b/app/main.c
@@ -128,7 +128,7 @@ void toggle_chan_scanlist(void)
 			g_eeprom.tx_vfo                     = vfo;
 
 			RADIO_select_vfos();
-			RADIO_ApplyOffset(g_tx_vfo);
+			RADIO_ApplyOffset(g_tx_vfo, false);
 			RADIO_ConfigureSquelchAndOutputPower(g_tx_vfo);
 			RADIO_setup_registers(true);
 
@@ -844,18 +844,8 @@ void MAIN_Key_UP_DOWN(bool key_pressed, bool key_held, scan_state_dir_t Directio
 			g_tx_vfo->freq_in_channel = BOARD_find_channel(g_tx_vfo->freq_config_rx.frequency);
 
 			SETTINGS_save_channel(g_tx_vfo->channel_save, g_eeprom.tx_vfo, g_tx_vfo, 1);
-			
-			RADIO_ApplyOffset(g_tx_vfo);
-			if (!g_tx_vfo->frequency_reverse)
-			{
-				g_tx_vfo->p_rx = &g_tx_vfo->freq_config_rx;
-				g_tx_vfo->p_tx = &g_tx_vfo->freq_config_tx;
-			}
-			else
-			{
-				g_tx_vfo->p_rx = &g_tx_vfo->freq_config_tx;
-				g_tx_vfo->p_tx = &g_tx_vfo->freq_config_rx;
-			}
+
+			RADIO_ApplyOffset(g_tx_vfo, true);
 			
 			#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
 //				UART_printf("save chan\r\n");
diff --git a/driver/bk4819.c b/driver/bk4819.c
index 62189dd..9daf65c 100644
--- a/driver/bk4819.c
+++ b/driver/bk4819.c
@@ -292,10 +292,10 @@ void BK4819_DisableAGC(void)
 	// <7:5>   LNA Gain
 	//         7 =   0dB
 	//         6 =  -2dB
-	//         5 =  -4dB
+	//         5 =  -4dB <<<
 	//         4 =  -6dB
 	//         3 =  -9dB
-	//         2 = -14dB <<<
+	//         2 = -14dB
 	//         1 = -19dB
 	//         0 = -24dB
 	//
@@ -321,61 +321,63 @@ void BK4819_DisableAGC(void)
 	BK4819_WriteRegister(0x10, 0x007A);  // 000000 00 011 11 010
 	BK4819_WriteRegister(0x14, 0x0019);  // 000000 00 000 11 001
 
-	// undocumented ?
+	// ??
 	BK4819_WriteRegister(0x49, 0x2A38);
 	BK4819_WriteRegister(0x7B, 0x8420);
 }
 
-void BK4819_EnableAGC(void)
-{
-	// TODO: See if this attenuates overloading
-	// signals as well as boosting weak ones
-	//
-	// REG_7E
-	//
-	// <15> 0 AGC Fix Mode.
-	// 1=Fix; 0=Auto.
-	//
-	// <14:12> 0b011 AGC Fix Index.
-	// 011=Max, then 010,001,000,111,110,101,100(min).
-	//
-	// <5:3> 0b101 DC Filter Band Width for Tx (MIC In).
-	// 000=Bypass DC filter;
-	//
-	// <2:0> 0b110 DC Filter Band Width for Rx (IF In).
-	// 000=Bypass DC filter;
-
-	BK4819_WriteRegister(0x7E,
-		(0u << 15) |      // 0  AGC fix mode
-		(3u << 12) |      // 3  AGC fix index
-		(5u <<  3) |      // 5  DC Filter band width for Tx (MIC In)
-		(6u <<  0));      // 6  DC Filter band width for Rx (I.F In)
-
-	// TBR: fagci has this listed as two values, agc_rssi and lna_peak_rssi
-	// This is why AGC appeared to do nothing as-is for Rx
-	//
-	// REG_62
-	//
-	// <15:8> 0xFF AGC RSSI
-	//
-	// <7:0> 0xFF LNA Peak RSSI
-	//
-	// TBR: Using S9+30 (173) and S9 (143) as suggested values
-	BK4819_WriteRegister(0x62, (173u << 8) | (143u << 0));
-
-	// AGC auto-adjusts the following LNA values, no need to set them ourselves
-	//BK4819_WriteRegister(0x13, (3u << 8) | (5u << 5) | (3u << 3) | (6u << 0));  // 000000 11 101 11 110
-	//BK4819_WriteRegister(0x12, 0x037B);  // 000000 11 011 11 011
-	//BK4819_WriteRegister(0x11, 0x027B);  // 000000 10 011 11 011
-	//BK4819_WriteRegister(0x10, 0x007A);  // 000000 00 011 11 010
-	//BK4819_WriteRegister(0x14, 0x0019);  // 000000 00 000 11 001
-
-	BK4819_WriteRegister(0x49, 0x2A38);
-	BK4819_WriteRegister(0x7B, 0x8420);
-
-	for (unsigned int i = 0; i < 8; i++)
-		BK4819_WriteRegister(0x06, ((i & 7u) << 13) | (0x4A << 7) | (0x36 << 0));
-}
+#ifndef ENABLE_AM_FIX
+	void BK4819_EnableAGC(void)
+	{
+		// TODO: See if this attenuates overloading
+		// signals as well as boosting weak ones
+		//
+		// REG_7E
+		//
+		// <15> 0 AGC Fix Mode.
+		// 1=Fix; 0=Auto.
+		//
+		// <14:12> 0b011 AGC Fix Index.
+		// 011=Max, then 010,001,000,111,110,101,100(min).
+		//
+		// <5:3> 0b101 DC Filter Band Width for Tx (MIC In).
+		// 000=Bypass DC filter;
+		//
+		// <2:0> 0b110 DC Filter Band Width for Rx (IF In).
+		// 000=Bypass DC filter;
+	
+		BK4819_WriteRegister(0x7E,
+			(0u << 15) |      // 0  AGC fix mode
+			(3u << 12) |      // 3  AGC fix index
+			(5u <<  3) |      // 5  DC Filter band width for Tx (MIC In)
+			(6u <<  0));      // 6  DC Filter band width for Rx (I.F In)
+	
+		// TBR: fagci has this listed as two values, agc_rssi and lna_peak_rssi
+		// This is why AGC appeared to do nothing as-is for Rx
+		//
+		// REG_62
+		//
+		// <15:8> 0xFF AGC RSSI
+		//
+		// <7:0> 0xFF LNA Peak RSSI
+		//
+		// TBR: Using S9+30 (173) and S9 (143) as suggested values
+		BK4819_WriteRegister(0x62, (173u << 8) | (143u << 0));
+	
+		// AGC auto-adjusts the following LNA values, no need to set them ourselves
+		//BK4819_WriteRegister(0x13, (3u << 8) | (5u << 5) | (3u << 3) | (6u << 0));  // 000000 11 101 11 110
+		//BK4819_WriteRegister(0x12, 0x037B);  // 000000 11 011 11 011
+		//BK4819_WriteRegister(0x11, 0x027B);  // 000000 10 011 11 011
+		//BK4819_WriteRegister(0x10, 0x007A);  // 000000 00 011 11 010
+		//BK4819_WriteRegister(0x14, 0x0019);  // 000000 00 000 11 001
+	
+		BK4819_WriteRegister(0x49, 0x2A38);
+		BK4819_WriteRegister(0x7B, 0x8420);
+	
+		for (unsigned int i = 0; i < 8; i++)
+			BK4819_WriteRegister(0x06, ((i & 7u) << 13) | (0x4A << 7) | (0x36 << 0));
+	}
+#endif
 
 void BK4819_set_GPIO_pin(bk4819_gpio_pin_t Pin, bool bSet)
 {
@@ -1939,6 +1941,9 @@ void BK4819_reset_fsk(void)
 
 		BK4819_WriteRegister(0x02, 0);    // clear interrupt flags
 
+		// set the almost full threshold
+		BK4819_WriteRegister(0x5E, (64u << 3) | (1u << 0));  // 0 ~ 127, 0 ~ 7
+
 		// set the packet size
 		BK4819_WriteRegister(0x5D, ((packet_size - 1) << 8));
 
@@ -2141,7 +2146,7 @@ void BK4819_reset_fsk(void)
 				(3u << 8) |			// 0 FSK RX gain
 									//   0 ~ 3
 									//
-				(3u << 6) |			// 0 ???
+				(0u << 6) |			// 0 ???
 									//   0 ~ 3
 									//
 				(0u << 4) |			// 0 FSK preamble type selection
@@ -2177,11 +2182,16 @@ void BK4819_reset_fsk(void)
 			BK4819_WriteRegister(0x5B, ((uint16_t)mdc1200_sync_suc_xor[2] << 8) | (mdc1200_sync_suc_xor[3] << 0));
 
 			// disable CRC
-			BK4819_WriteRegister(0x5C, 0x5625);
+			BK4819_WriteRegister(0x5C, 0x5625);   // 010101100 0 100101
+//			BK4819_WriteRegister(0x5C, 0xAA30);   // 101010100 0 110000
 
-			{	// packet size .. 14 bytes - size of a single mdc1200 packet
-				uint16_t size = sizeof(mdc1200_sync_suc_xor) + 14;
+			// set the almost full threshold
+			BK4819_WriteRegister(0x5E, (64u << 3) | (1u << 0));  // 0 ~ 127, 0 ~ 7
+
+			{	// packet size .. sync + 14 bytes - size of a single mdc1200 packet
+				uint16_t size = sizeof(mdc1200_sync_suc_xor) + (MDC1200_FEC_K * 2);
 				size -= (fsk_reg59 & (1u << 3)) ? 4 : 2; 
+				size = ((size + 1) / 2) * 2;             // round up to even, else FSK RX doesn't work
 				BK4819_WriteRegister(0x5D, ((size - 1) << 8));
 			}
 	
@@ -2250,7 +2260,7 @@ void BK4819_reset_fsk(void)
 
 		const uint16_t tx_dev = BK4819_ReadRegister(0x40);
 	//	BK4819_WriteRegister(0x40, (0u << 12) | (1232 << 0));   // 000 0 010011010000
-		BK4819_WriteRegister(0x40, (tx_dev & 0xf000) | (1050 << 0));  // reduce the deviation a little
+		BK4819_WriteRegister(0x40, (tx_dev & 0xf000) | (1000 << 0));  // reduce the deviation a little
 
 		// REG_2B   0
 		//
@@ -2294,7 +2304,7 @@ void BK4819_reset_fsk(void)
 			(1u  <<  1) |    // enable  TX DSP
 			(0u  <<  0));    // disable RX DSP
 
-		SYSTEM_DelayMs(20);
+		SYSTEM_DelayMs(10);
 
 		// *******************************************
 
@@ -2464,8 +2474,8 @@ void BK4819_reset_fsk(void)
 		//
 		// disable CRC
 		//
-	//	BK4819_WriteRegister(0x5C, 0xAA30);   // 101010100 0 110000
-		BK4819_WriteRegister(0x5C, 0);        // setting to '0' doesn't make any difference !
+//		BK4819_WriteRegister(0x5C, 0x5625);   // 010101100 0 100101
+		BK4819_WriteRegister(0x5C, 0xAA30);   // 101010100 0 110000
 
 		{	// load the entire packet data into the TX FIFO buffer
 			unsigned int i;
@@ -2477,7 +2487,7 @@ void BK4819_reset_fsk(void)
 		// enable tx interrupt
 		BK4819_WriteRegister(0x3F, BK4819_REG_3F_FSK_TX_FINISHED);
 
-		// enable TX
+		// enable FSK TX
 		BK4819_WriteRegister(0x59, (1u << 11) | fsk_reg59);
 
 		{	// packet time is ..
diff --git a/firmware.bin b/firmware.bin
index eeae636..1ea8d84 100644
Binary files a/firmware.bin and b/firmware.bin differ
diff --git a/firmware.packed.bin b/firmware.packed.bin
index 99314f6..3327a26 100644
Binary files a/firmware.packed.bin and b/firmware.packed.bin differ
diff --git a/functions.c b/functions.c
index d8e87c1..7c35ea3 100644
--- a/functions.c
+++ b/functions.c
@@ -265,12 +265,11 @@ void FUNCTION_Select(function_type_t Function)
 					SYSTEM_DelayMs(2);
 
 					GPIO_SetBit(&GPIOC->DATA, GPIOC_PIN_SPEAKER);
+					g_speaker_enabled = true;
 
 					#ifdef ENABLE_ALARM
 						g_alarm_tone_counter_10ms = 0;
 					#endif
-
-					g_speaker_enabled = true;
 					break;
 				}
 				else
@@ -280,7 +279,10 @@ void FUNCTION_Select(function_type_t Function)
 			{
 			#ifdef ENABLE_MDC1200
 				if (g_current_vfo->mdc1200_mode == MDC1200_MODE_BOT || g_current_vfo->mdc1200_mode == MDC1200_MODE_BOTH)
+				{
+					SYSTEM_DelayMs(150);
 					BK4819_send_MDC1200(MDC1200_OP_CODE_PTT_ID, 0x80, g_eeprom.mdc1200_id);
+				}
 				else
 			#endif
 				if (g_current_vfo->dtmf_ptt_id_tx_mode == PTT_ID_APOLLO)
diff --git a/main.c b/main.c
index a7a8e0d..bbeb06d 100644
--- a/main.c
+++ b/main.c
@@ -65,9 +65,11 @@ void Main(void)
 		| SYSCON_DEV_CLK_GATE_AES_BITS_ENABLE;
 
 	SYSTICK_Init();
+	
 #ifdef ENABLE_UART
 	UART_Init();
 #endif
+
 	BOARD_Init();
 
 	#if defined(ENABLE_UART)
@@ -91,11 +93,11 @@ void Main(void)
 	BK4819_Init();
 
 	#if defined(ENABLE_UART)
-		UART_printf("bk4819  id %04X  rev %04X\r\n", BK4819_ReadRegister(0x00), BK4819_ReadRegister(0x01));
+		UART_printf("BK4819  id %04X  rev %04X\r\n", BK4819_ReadRegister(0x00), BK4819_ReadRegister(0x01));
 	#endif
 	
 #ifdef ENABLE_MDC1200
-	mdc1200_init();
+	MDC1200_init();
 #endif
 
 	BOARD_ADC_GetBatteryInfo(&g_usb_current_voltage, &g_usb_current);
diff --git a/mdc1200.c b/mdc1200.c
index 0283908..491e68d 100644
--- a/mdc1200.c
+++ b/mdc1200.c
@@ -1,6 +1,7 @@
 
 #include <string.h>
 
+#include "driver/bk4819.h"
 #include "driver/crc.h"
 #if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
 	#include "driver/uart.h"
@@ -8,8 +9,6 @@
 #include "mdc1200.h"
 #include "misc.h"
 
-#define FEC_K   7     	// R=1/2 K=7 convolutional coder
-
 // **********************************************************
 
 // pre-amble and sync pattern
@@ -136,7 +135,7 @@ void error_correction(void *data)
 	uint8_t syn;
 	uint8_t *data8 = (uint8_t *)data;
 
-	for (i = 0, shift_reg = 0, syn = 0; i < FEC_K; i++)
+	for (i = 0, shift_reg = 0, syn = 0; i < MDC1200_FEC_K; i++)
 	{
 		const uint8_t bi = data8[i];
 		int bit_num;
@@ -147,7 +146,7 @@ void error_correction(void *data)
 
 			shift_reg = (shift_reg << 1) | ((bi >> bit_num) & 1u);
 			b         = ((shift_reg >> 6) ^ (shift_reg >> 5) ^ (shift_reg >> 2) ^ (shift_reg >> 0)) & 1u;
-			syn       = (syn << 1) | (((b ^ (data8[i + FEC_K] >> bit_num)) & 1u) ? 1u : 0u);
+			syn       = (syn << 1) | (((b ^ (data8[i + MDC1200_FEC_K] >> bit_num)) & 1u) ? 1u : 0u);
 
 			if (syn & 0x80) k++;
 			if (syn & 0x20) k++;
@@ -205,7 +204,7 @@ bool decode_data(void *data)
 		unsigned int i;
 		unsigned int k;
 		unsigned int m;
-		uint8_t deinterleaved[(FEC_K * 2) * 8];  // temp individual bit storage
+		uint8_t deinterleaved[(MDC1200_FEC_K * 2) * 8];  // temp individual bit storage
 
 		// interleave order
 		//  0, 16, 32, 48, 64, 80,  96,
@@ -228,7 +227,7 @@ bool decode_data(void *data)
 		// de-interleave the received bits
 		for (i = 0, k = 0; i < 16; i++)
 		{
-			for (m = 0; m < FEC_K; m++)
+			for (m = 0; m < MDC1200_FEC_K; m++)
 			{
 				const unsigned int n = (m * 16) + i;
 				deinterleaved[k++] = (data8[n >> 3] >> ((7 - n) & 7u)) & 1u;
@@ -236,7 +235,7 @@ bool decode_data(void *data)
 		}
 
 		// copy the de-interleaved bits back into the data buffer
-		for (i = 0, m = 0; i < (FEC_K * 2); i++)
+		for (i = 0, m = 0; i < (MDC1200_FEC_K * 2); i++)
 		{
 			unsigned int k;
 			uint8_t b = 0;
@@ -302,7 +301,7 @@ uint8_t * encode_data(void *data)
 	{	// add the FEC bits to the end of the data
 		unsigned int i;
 		uint8_t shift_reg = 0;
-		for (i = 0; i < FEC_K; i++)
+		for (i = 0; i < MDC1200_FEC_K; i++)
 		{
 			unsigned int  bit_num;
 			const uint8_t bi = data8[i];
@@ -312,7 +311,7 @@ uint8_t * encode_data(void *data)
 				shift_reg = (shift_reg << 1) | ((bi >> bit_num) & 1u);
 				bo |= (((shift_reg >> 6) ^ (shift_reg >> 5) ^ (shift_reg >> 2) ^ (shift_reg >> 0)) & 1u) << bit_num;
 			}
-			data8[FEC_K + i] = bo;
+			data8[MDC1200_FEC_K + i] = bo;
 		}
 	}
 
@@ -320,7 +319,7 @@ uint8_t * encode_data(void *data)
 /*
 	#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
 	{
-		const unsigned int size = FEC_K * 2;
+		const unsigned int size = MDC1200_FEC_K * 2;
 		unsigned int i;
 		UART_printf("mdc1200 tx1 %u ", size);
 		for (i = 0; i < size; i++)
@@ -333,7 +332,7 @@ uint8_t * encode_data(void *data)
 
 		unsigned int i;
 		unsigned int k;
-		uint8_t interleaved[(FEC_K * 2) * 8];   // temp individual bit storage
+		uint8_t interleaved[(MDC1200_FEC_K * 2) * 8];   // temp individual bit storage
 
 		// interleave order
 		//  0, 16, 32, 48, 64, 80,  96,
@@ -354,7 +353,7 @@ uint8_t * encode_data(void *data)
 		// 15, 31, 47, 63, 79, 95, 111
 
 		// bit interleaver
-		for (i = 0, k = 0; i < (FEC_K * 2); i++)
+		for (i = 0, k = 0; i < (MDC1200_FEC_K * 2); i++)
 		{
 			unsigned int bit_num;
 			const uint8_t b = data8[i];
@@ -368,7 +367,7 @@ uint8_t * encode_data(void *data)
 		}
 
 		// copy the interleaved bits back to the data buffer
-		for (i = 0, k = 0; i < (FEC_K * 2); i++)
+		for (i = 0, k = 0; i < (MDC1200_FEC_K * 2); i++)
 		{
 			int bit_num;
 			uint8_t b = 0;
@@ -379,7 +378,7 @@ uint8_t * encode_data(void *data)
 		}
 	}
 
-	return data8 + (FEC_K * 2);
+	return data8 + (MDC1200_FEC_K * 2);
 }
 
 unsigned int MDC1200_encode_single_packet(void *data, const uint8_t op, const uint8_t arg, const uint16_t unit_id)
@@ -483,7 +482,7 @@ void MDC1200_reset_rx(void)
 	memset(&rx, 0, sizeof(rx));
 }
 
-bool MDC1200_process_rx(
+bool MDC1200_process_rx_data(
 	const void *buffer,
 	const unsigned int size,
 	//const bool inverted,
@@ -494,30 +493,30 @@ bool MDC1200_process_rx(
 	const uint8_t *buffer8 = (const uint8_t *)buffer;
 	unsigned int   index;
 
-	// FB 72 40 99 A7
-	// FB 72 40 99 A7   BF 3B 4F CD 45 06 CC D1 CC D1 CC D1 CC 2B
-	// FB 72 40 99 A7   BA 24 FC F8 43 05 CA D1 CC FF 1B FF 1B 2B
+	// 04 8D BF 66 58   sync
+	// FB 72 40 99 A7   inverted sync
+	//
+	// 04 8D BF 66 58   40 C4 B0 32 BA F9 33 18 35 08 83 F6 0C 36 .. 80 87 20 23 2C AE 22 10 26 0F 02 A4 08 24
+	// 04 8D BF 66 58   45 DB 03 07 BC FA 35 2E 33 0E 83 0E 83 69 .. 86 92 02 05 28 AC 26 34 22 0B 02 0B 02 4E
 
 	memset(&rx, 0, sizeof(rx));
 
 	for (index = 0; index < size; index++)
 	{
-		unsigned int i;
-		int          bit;
-
+		int           bit;
 		const uint8_t rx_byte = buffer8[index];
 
 		for (bit = 7; bit >= 0; bit--)
 		{
+			unsigned int i;
+
 			rx.prev_bit = rx.bit;
 
 			rx.bit = (rx_byte >> bit) & 1u;
 
-			rx.xor_bit = (rx.xor_bit ^ rx.bit) & 1u;
-			if (rx.stage > 0 && rx.inverted_sync)
-				rx.xor_bit ^= 1u;
+			rx.xor_bit = (rx.xor_bit ^ rx.bit) & 1u;  // toggle our bit if the rx bit is high
 
-			rx.shift_reg = (rx.shift_reg << 1) | (rx.xor_bit & 1u);
+			rx.shift_reg = (rx.shift_reg << 1) | rx.xor_bit;
 			rx.bit_count++;
 
 			// *********
@@ -527,7 +526,7 @@ bool MDC1200_process_rx(
 
 				const unsigned int sync_bit_ok_threshold = 32;
 
-				if (rx.bit_count >= sync_bit_ok_threshold)
+				if (rx.bit_count >= 40)
 				{
 					// 40-bit sync pattern
 					uint64_t sync_nor = 0x07092a446fu;            // normal
@@ -546,16 +545,23 @@ bool MDC1200_process_rx(
 					nor_count = 40 - nor_count;
 					inv_count = 40 - inv_count;
 
+					#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+					//	UART_SendText("mdc1200 rx sync pat ");
+					//	for (i = 64; i > 0; i--)
+					//		UART_printf("%u", (uint8_t)((rx.shift_reg >> (i - 1))) & 1u);
+					//	UART_SendText("\r\n");
+					#endif
+
 					if (nor_count >= sync_bit_ok_threshold || inv_count >= sync_bit_ok_threshold)
 					{	// good enough
 
 						rx.inverted_sync = (inv_count > nor_count) ? true : false;
 						rx.data_index    = 0;
 						rx.bit_count     = 0;
-						rx.stage++;
+						rx.stage         = 1;
 
 						#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-							UART_printf("mdc1200 rx sync %s\r\n", rx.inverted_sync ? "inv" : "nor");
+							//UART_printf("mdc1200 rx sync %s\r\n", rx.inverted_sync ? "inv" : "nor");
 						#endif
 					}
 				}
@@ -568,15 +574,13 @@ bool MDC1200_process_rx(
 
 			rx.bit_count = 0;
 
-			// 07 09 2A 44 6F 94 9C 22 20 32 A4 1A 37 1E 3A 00 98 2C 84
-
 			rx.data[rx.data_index++] = rx.shift_reg & 0xff;  // save the last 8 bits
 
-			if (rx.data_index < (FEC_K * 2))
+			if (rx.data_index < (MDC1200_FEC_K * 2))
 				continue;
 
 			#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-				UART_SendText("mdc1200 rx ");
+				UART_SendText("mdc1200 dec ");
 				for (i = 0; i < rx.data_index; i++)
 					UART_printf(" %02X", rx.data[i]);
 				UART_SendText("\r\n");
@@ -585,9 +589,9 @@ bool MDC1200_process_rx(
 			if (!decode_data(rx.data))
 			{
 				MDC1200_reset_rx();
-	
+
 				#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-					UART_SendText("mdc1200 rx decode error\r\n");
+					UART_SendText("mdc1200 dec err\r\n");
 				#endif
 
 				continue;
@@ -596,10 +600,10 @@ bool MDC1200_process_rx(
 			// extract the info from the packet
 			*op      = rx.data[0];
 			*arg     = rx.data[1];
-			*unit_id = ((uint16_t)rx.data[3] << 8) | (rx.data[2] << 0);
+			*unit_id = ((uint16_t)rx.data[2] << 8) | (rx.data[3] << 0);
 
 			#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
-				UART_printf("mdc1200 rx  op %02X  arg %02X  id %04X\r\n", *op, *arg, *unit_id);
+				//UART_printf("mdc1200  op %02X  arg %02X  id %04X\r\n", *op, *arg, *unit_id);
 			#endif
 
 			// reset the detector
@@ -614,6 +618,149 @@ bool MDC1200_process_rx(
 	return false;
 }
 
+uint8_t      mdc1200_rx_buffer[sizeof(mdc1200_sync_suc_xor) + (MDC1200_FEC_K * 2)];
+unsigned int mdc1200_rx_buffer_index = 0;
+
+uint8_t  mdc1200_op;
+uint8_t  mdc1200_arg;
+uint16_t mdc1200_unit_id;
+uint8_t  mdc1200_rx_ready_tick_500ms;
+
+void MDC1200_process_rx(const uint16_t interrupt_bits)
+{
+	const uint16_t rx_sync_flags   = BK4819_ReadRegister(0x0B);
+	const uint16_t fsk_reg59       = BK4819_ReadRegister(0x59) & ~((1u << 15) | (1u << 14) | (1u << 12) | (1u << 11));
+
+	const bool rx_sync             = (interrupt_bits & BK4819_REG_02_FSK_RX_SYNC) ? true : false;
+	const bool rx_sync_neg         = (rx_sync_flags & (1u << 7)) ? true : false;
+	const bool rx_sync_pos         = (rx_sync_flags & (1u << 6)) ? true : false;
+	const bool rx_fifo_almost_full = (interrupt_bits & BK4819_REG_02_FSK_FIFO_ALMOST_FULL) ? true : false;
+	const bool rx_finished         = (interrupt_bits & BK4819_REG_02_FSK_RX_FINISHED) ? true : false;
+
+	const unsigned int sync_size   = (fsk_reg59 & (1u << 3)) ? 4 : 2;
+
+	if (rx_sync)
+	{
+//		BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, true);   // LED on
+
+		//mdc1200_rx_ready = false;
+
+		mdc1200_rx_buffer_index = 0;
+
+		{	// precede the data with the missing sync pattern (it's not part of the packet data)
+			unsigned int i;
+			memset(mdc1200_rx_buffer, 0, sizeof(mdc1200_rx_buffer));
+			for (i = 0; i < sync_size; i++)
+				mdc1200_rx_buffer[mdc1200_rx_buffer_index++] = mdc1200_sync_suc_xor[i] ^ (rx_sync_neg ? 0xFF : 0x00);
+		}
+
+		#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+			UART_SendText("mdc1200 syn");
+		#endif
+
+		if (rx_sync_neg)
+		{	// RX sync neg found
+			#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+				UART_SendText("-");
+			#endif
+		}
+
+		if (rx_sync_pos)
+		{	// RX sync pos found
+			#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+				UART_SendText("+");
+			#endif
+		}
+
+		#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+			UART_SendText("\r\n");
+		#endif
+	}
+
+	if (rx_fifo_almost_full)
+	{
+		unsigned int i;
+		const unsigned int count = BK4819_ReadRegister(0x5E) & (7u << 0);  // almost full threshold
+
+		#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+			UART_printf("mdc1200 full %2u %2u ", mdc1200_rx_buffer_index, count);
+		#endif
+
+		// fetch RX'ed data
+		for (i = 0; i < count; i++)
+		{
+			const uint16_t word = BK4819_ReadRegister(0x5F) ^ (rx_sync_neg ? 0xFFFF : 0x0000);
+
+			#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+				UART_printf(" %04X", word);
+			#endif
+
+			if (mdc1200_rx_buffer_index < sizeof(mdc1200_rx_buffer))
+				mdc1200_rx_buffer[mdc1200_rx_buffer_index++] = (word >> 0) & 0xff;
+
+			if (mdc1200_rx_buffer_index < sizeof(mdc1200_rx_buffer))
+				mdc1200_rx_buffer[mdc1200_rx_buffer_index++] = (word >> 8) & 0xff;
+		}
+
+		#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+			UART_SendText("\r\n");
+		#endif
+
+		if (mdc1200_rx_buffer_index >= sizeof(mdc1200_rx_buffer))
+		{
+			BK4819_WriteRegister(0x59, (1u << 15) | (1u << 14) | fsk_reg59);
+			BK4819_WriteRegister(0x59, (1u << 12) | fsk_reg59);
+
+			#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+			{
+				unsigned int i;
+				UART_SendText("mdc1200 ");
+				for (i = 0; i < mdc1200_rx_buffer_index; i++)
+					UART_printf(" %02X", mdc1200_rx_buffer[i]);
+				UART_SendText("\r\n");
+			}
+			#endif
+
+//			if (!g_squelch_open)
+//				BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, false);  // LED off
+
+			if (MDC1200_process_rx_data(
+				mdc1200_rx_buffer,
+				mdc1200_rx_buffer_index,
+//				(sync_flags & (1u << 7)) ? true : false, // true if the sync pattern is bit inverted
+				&mdc1200_op,
+				&mdc1200_arg,
+				&mdc1200_unit_id))
+			{
+				mdc1200_rx_ready_tick_500ms = 2 * 6;  // 6 seconds
+
+				g_update_display = true;
+				
+				#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+					UART_printf("MDC1200  op %02X  arg %02X  id %04X\r\n", mdc1200_op, mdc1200_arg, mdc1200_unit_id);
+				#endif
+			}
+
+			mdc1200_rx_buffer_index = 0;
+		}
+	}
+
+	if (rx_finished)
+	{
+		mdc1200_rx_buffer_index = 0;
+
+//		if (!g_squelch_open)
+//			BK4819_set_GPIO_pin(BK4819_GPIO6_PIN2_GREEN, false);  // LED off
+
+		BK4819_WriteRegister(0x59, (1u << 15) | (1u << 14) | fsk_reg59);
+		BK4819_WriteRegister(0x59, (1u << 12) | fsk_reg59);
+
+		#if defined(ENABLE_UART) && defined(ENABLE_UART_DEBUG)
+			UART_SendText("mdc1200 fin\r\n");
+		#endif
+	}
+}
+
 // **********************************************************
 
 /*
@@ -625,7 +772,7 @@ void test(void)
 }
 */
 
-void mdc1200_init(void)
+void MDC1200_init(void)
 {
 	memcpy(mdc1200_sync_suc_xor, mdc1200_sync, sizeof(mdc1200_sync));
 	xor_modulation(mdc1200_sync_suc_xor, sizeof(mdc1200_sync_suc_xor));
diff --git a/mdc1200.h b/mdc1200.h
index db44afe..19e82e6 100644
--- a/mdc1200.h
+++ b/mdc1200.h
@@ -5,6 +5,8 @@
 #include <stdint.h>
 #include <stdbool.h>
 
+#define MDC1200_FEC_K   7     	// R=1/2 K=7 convolutional coder
+
 // 0x00 (0x81) emergency alarm
 // 0x20 (0x00) emergency alarm ack
 //
@@ -90,18 +92,15 @@ typedef enum mdc1200_op_code_e mdc1200_op_code_t;
 extern const uint8_t mdc1200_sync[5];
 extern uint8_t mdc1200_sync_suc_xor[sizeof(mdc1200_sync)];
 
-unsigned int MDC1200_encode_single_packet(void *data, const uint8_t op, const uint8_t arg, const uint16_t unit_id);
+extern uint8_t  mdc1200_op;
+extern uint8_t  mdc1200_arg;
+extern uint16_t mdc1200_unit_id;
+extern uint8_t  mdc1200_rx_ready_tick_500ms;
+
+unsigned int   MDC1200_encode_single_packet(void *data, const uint8_t op, const uint8_t arg, const uint16_t unit_id);
 //unsigned int MDC1200_encode_double_packet(void *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);
-
-void MDC1200_reset_rx(void);
-bool MDC1200_process_rx(
-	const void *buffer,
-	const unsigned int size,
-	//const bool inverted,
-	uint8_t *op,
-	uint8_t *arg,
-	uint16_t *unit_id);
-
-void mdc1200_init(void);
+void           MDC1200_reset_rx(void);
+void           MDC1200_process_rx(const uint16_t interrupt_bits);
+void           MDC1200_init(void);
 
 #endif
diff --git a/radio.c b/radio.c
index 99af858..250fac4 100644
--- a/radio.c
+++ b/radio.c
@@ -366,24 +366,13 @@ void RADIO_configure_channel(const unsigned int VFO, const unsigned int configur
 		p_vfo->tx_offset_freq = FREQUENCY_floor_to_step(p_vfo->tx_offset_freq + (p_vfo->step_freq / 2), p_vfo->step_freq, 0, p_vfo->tx_offset_freq + p_vfo->step_freq);
 	}
 
-	RADIO_ApplyOffset(p_vfo);
+	RADIO_ApplyOffset(p_vfo, true);
 
 	// channel name
 	memset(p_vfo->name, 0, sizeof(p_vfo->name));
 	if (Channel <= USER_CHANNEL_LAST)
 		EEPROM_ReadBuffer(0x0F50 + (Channel * 16), p_vfo->name, 10);	// only 10 bytes used
 
-	if (!p_vfo->frequency_reverse)
-	{
-		p_vfo->p_rx = &p_vfo->freq_config_rx;
-		p_vfo->p_tx = &p_vfo->freq_config_tx;
-	}
-	else
-	{
-		p_vfo->p_rx = &p_vfo->freq_config_tx;
-		p_vfo->p_tx = &p_vfo->freq_config_rx;
-	}
-
 	if (p_vfo->am_mode)
 	{	// freq/chan is in AM mode
 		// disable stuff, even though it can all still be used with AM ???
@@ -583,7 +572,7 @@ void RADIO_ConfigureSquelchAndOutputPower(vfo_info_t *p_vfo)
 	// *******************************
 }
 
-void RADIO_ApplyOffset(vfo_info_t *p_vfo)
+void RADIO_ApplyOffset(vfo_info_t *p_vfo, const bool set_pees)
 {
 	uint32_t Frequency = p_vfo->freq_config_rx.frequency;
 
@@ -606,6 +595,20 @@ void RADIO_ApplyOffset(vfo_info_t *p_vfo)
 		Frequency = FREQ_BAND_TABLE[ARRAY_SIZE(FREQ_BAND_TABLE) - 1].upper;
 
 	p_vfo->freq_config_tx.frequency = Frequency;
+
+	if (set_pees)
+	{
+		if (!p_vfo->frequency_reverse)
+		{
+			p_vfo->p_rx = &p_vfo->freq_config_rx;
+			p_vfo->p_tx = &p_vfo->freq_config_tx;
+		}
+		else
+		{
+			p_vfo->p_rx = &p_vfo->freq_config_tx;
+			p_vfo->p_tx = &p_vfo->freq_config_rx;
+		}
+	}
 }
 
 static void RADIO_SelectCurrentVfo(void)
diff --git a/radio.h b/radio.h
index 91191e4..6c18dcf 100644
--- a/radio.h
+++ b/radio.h
@@ -147,7 +147,7 @@ uint8_t  RADIO_FindNextChannel(uint8_t ChNum, scan_state_dir_t Direction, bool b
 void     RADIO_InitInfo(vfo_info_t *p_vfo, const uint8_t ChannelSave, const uint32_t Frequency);
 void     RADIO_configure_channel(const unsigned int VFO, const unsigned int configure);
 void     RADIO_ConfigureSquelchAndOutputPower(vfo_info_t *p_vfo);
-void     RADIO_ApplyOffset(vfo_info_t *p_vfo);
+void     RADIO_ApplyOffset(vfo_info_t *p_vfo, const bool set_pees);
 void     RADIO_select_vfos(void);
 void     RADIO_setup_registers(bool switch_to_function_foreground);
 #ifdef ENABLE_NOAA
diff --git a/ui/main.c b/ui/main.c
index d59c0aa..fcc7b68 100644
--- a/ui/main.c
+++ b/ui/main.c
@@ -14,9 +14,9 @@
  *     limitations under the License.
  */
 
-	#pragma GCC diagnostic push
-	#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
-	#pragma GCC diagnostic pop
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+#pragma GCC diagnostic pop
 
 #include <string.h>
 #include <stdlib.h>  // abs()
@@ -34,6 +34,9 @@
 #include "font.h"
 #include "functions.h"
 #include "helper/battery.h"
+#ifdef ENABLE_MDC1200
+	#include "mdc1200.h"
+#endif
 #include "misc.h"
 #include "radio.h"
 #include "settings.h"
@@ -43,7 +46,7 @@
 #include "ui/menu.h"
 #include "ui/ui.h"
 
-center_line_t center_line = CENTER_LINE_NONE;
+center_line_t g_center_line = CENTER_LINE_NONE;
 
 // ***************************************************************************
 
@@ -86,7 +89,7 @@ void draw_bar(uint8_t *line, const int len, const int max_width)
 		if (g_current_function != FUNCTION_TRANSMIT || g_screen_to_display != DISPLAY_MAIN)
 			return false;
 
-		if (center_line != CENTER_LINE_NONE && center_line != CENTER_LINE_TX_TIMEOUT)
+		if (g_center_line != CENTER_LINE_NONE && g_center_line != CENTER_LINE_TX_TIMEOUT)
 			return false;
 
 		if (g_eeprom.tx_timeout_timer == 0)
@@ -178,7 +181,7 @@ void UI_drawBars(uint8_t *p, const unsigned int level)
 		if (g_current_function != FUNCTION_TRANSMIT || g_screen_to_display != DISPLAY_MAIN)
 			return false;
 
-		if (center_line != CENTER_LINE_NONE && center_line != CENTER_LINE_AUDIO_BAR)
+		if (g_center_line != CENTER_LINE_NONE && g_center_line != CENTER_LINE_AUDIO_BAR)
 			return false;
 
 		if (g_dtmf_call_state != DTMF_CALL_STATE_NONE)
@@ -304,7 +307,7 @@ void UI_drawBars(uint8_t *p, const unsigned int level)
 void UI_update_rssi(const int16_t rssi, const int vfo)
 {
 #ifdef ENABLE_RX_SIGNAL_BAR
-	if (center_line == CENTER_LINE_RSSI)
+	if (g_center_line == CENTER_LINE_RSSI)
 	{	// optional larger RSSI dBm, S-point and bar level
 		if (g_current_function == FUNCTION_RECEIVE || g_current_function == FUNCTION_MONITOR)
 		{
@@ -434,7 +437,7 @@ void UI_DisplayMain(void)
 	char               str[22];
 	unsigned int       vfo_num;
 
-	center_line = CENTER_LINE_NONE;
+	g_center_line = CENTER_LINE_NONE;
 
 //	#ifdef SINGLE_VFO_CHAN
 //		const bool single_vfo = (g_eeprom.dual_watch == DUAL_WATCH_OFF && g_eeprom.cross_vfo_rx_tx == CROSS_BAND_OFF) ? true : false;
@@ -548,7 +551,7 @@ void UI_DisplayMain(void)
 				str[16] = 0;
 				UI_PrintString(str, 2, 0, 2 + (vfo_num * 3), 8);
 
-				center_line = CENTER_LINE_IN_USE;
+				g_center_line = CENTER_LINE_IN_USE;
 				continue;
 			}
 
@@ -665,7 +668,7 @@ void UI_DisplayMain(void)
 		{	// user entering a frequency
 			UI_DisplayFrequency(g_input_box, 32, line, true, false);
 
-//			center_line = CENTER_LINE_IN_USE;
+//			g_center_line = CENTER_LINE_IN_USE;
 		}
 		else
 		{
@@ -906,7 +909,9 @@ void UI_DisplayMain(void)
 			UI_PrintStringSmall("SCR", LCD_WIDTH + 106, 0, line + 1);
 	}
 
-	if (center_line == CENTER_LINE_NONE)
+	if (g_center_line == CENTER_LINE_NONE &&
+		g_screen_to_display == DISPLAY_MAIN &&
+		g_dtmf_call_state == DTMF_CALL_STATE_NONE)
 	{	// we're free to use the middle line
 
 		const bool rx = (g_current_function == FUNCTION_RECEIVE ||
@@ -917,7 +922,7 @@ void UI_DisplayMain(void)
 			// show the TX timeout count down
 			if (UI_DisplayTXCountdown(false))
 			{
-				center_line = CENTER_LINE_TX_TIMEOUT;
+				g_center_line = CENTER_LINE_TX_TIMEOUT;
 			}
 			else
 		#endif
@@ -926,7 +931,21 @@ void UI_DisplayMain(void)
 			// show the TX audio level
 			if (UI_DisplayAudioBar(false))
 			{
-				center_line = CENTER_LINE_AUDIO_BAR;
+				g_center_line = CENTER_LINE_AUDIO_BAR;
+			}
+			else
+		#endif
+
+		#ifdef ENABLE_MDC1200
+			if (mdc1200_rx_ready_tick_500ms > 0)
+			{
+				g_center_line = CENTER_LINE_MDC1200;
+				sprintf(str, "MDC1200 %02X %02X %04X", mdc1200_op, mdc1200_arg, mdc1200_unit_id);
+				#ifdef ENABLE_SMALL_BOLD
+					UI_PrintStringSmallBold(str, 2, 0, 3);
+				#else
+					UI_PrintStringSmall(str, 2, 0, 3);
+				#endif
 			}
 			else
 		#endif
@@ -935,10 +954,7 @@ void UI_DisplayMain(void)
 			// show the AM-FIX debug data
 			if (rx && g_eeprom.vfo_info[g_eeprom.rx_vfo].am_mode && g_setting_am_fix)
 			{
-				if (g_screen_to_display != DISPLAY_MAIN || g_dtmf_call_state != DTMF_CALL_STATE_NONE)
-					return;
-
-				center_line = CENTER_LINE_AM_FIX_DATA;
+				g_center_line = CENTER_LINE_AM_FIX_DATA;
 				AM_fix_print_data(g_eeprom.rx_vfo, str);
 				UI_PrintStringSmall(str, 2, 0, 3);
 			}
@@ -949,7 +965,7 @@ void UI_DisplayMain(void)
 			// show the RX RSSI dBm, S-point and signal strength bar graph
 			if (rx && g_setting_rssi_bar)
 			{
-				center_line = CENTER_LINE_RSSI;
+				g_center_line = CENTER_LINE_RSSI;
 				UI_DisplayRSSIBar(g_current_rssi[g_eeprom.rx_vfo], false);
 			}
 			else
@@ -966,7 +982,7 @@ void UI_DisplayMain(void)
 					if (g_screen_to_display != DISPLAY_MAIN || g_dtmf_call_state != DTMF_CALL_STATE_NONE)
 						return;
 
-					center_line = CENTER_LINE_DTMF_DEC;
+					g_center_line = CENTER_LINE_DTMF_DEC;
 
 					strcpy(str, "DTMF ");
 					strcat(str, g_dtmf_rx_live + idx);
@@ -981,7 +997,7 @@ void UI_DisplayMain(void)
 					if (g_screen_to_display != DISPLAY_MAIN || g_dtmf_call_state != DTMF_CALL_STATE_NONE)
 						return;
 
-					center_line = CENTER_LINE_DTMF_DEC;
+					g_center_line = CENTER_LINE_DTMF_DEC;
 
 					strcpy(str, "DTMF ");
 					strcat(str, g_dtmf_rx + idx);
@@ -996,7 +1012,7 @@ void UI_DisplayMain(void)
 					if (g_screen_to_display != DISPLAY_MAIN || g_dtmf_call_state != DTMF_CALL_STATE_NONE)
 						return;
 
-					center_line = CENTER_LINE_CHARGE_DATA;
+					g_center_line = CENTER_LINE_CHARGE_DATA;
 
 					sprintf(str, "Charge %u.%02uV %u%%",
 						g_battery_voltage_average / 100, g_battery_voltage_average % 100,
diff --git a/ui/main.h b/ui/main.h
index fa22e5b..3ac9ffb 100644
--- a/ui/main.h
+++ b/ui/main.h
@@ -25,11 +25,12 @@ enum center_line_e {
 	CENTER_LINE_RSSI,
 	CENTER_LINE_AM_FIX_DATA,
 	CENTER_LINE_DTMF_DEC,
-	CENTER_LINE_CHARGE_DATA
+	CENTER_LINE_CHARGE_DATA,
+	CENTER_LINE_MDC1200
 };
 typedef enum center_line_e center_line_t;
 
-extern center_line_t center_line;
+extern center_line_t g_center_line;
 
 #ifdef ENABLE_TX_TIMEOUT_BAR
 	bool UI_DisplayTXCountdown(const bool now);