From 400fdb3cc6be6d3ae648586b5f7d95abe1487b73 Mon Sep 17 00:00:00 2001
From: pascallanger <pascal_langer@yahoo.fr>
Date: Sun, 27 Oct 2019 16:44:36 +0100
Subject: [PATCH] FrSkyX LBT RSSI timing improvement

---
 Multiprotocol/FrSkyX_cc2500.ino | 92 ++++++++++++++++-----------------
 Multiprotocol/_Config.h         |  5 +-
 2 files changed, 48 insertions(+), 49 deletions(-)

diff --git a/Multiprotocol/FrSkyX_cc2500.ino b/Multiprotocol/FrSkyX_cc2500.ino
index ac66992..06adf4c 100644
--- a/Multiprotocol/FrSkyX_cc2500.ino
+++ b/Multiprotocol/FrSkyX_cc2500.ino
@@ -297,51 +297,8 @@ uint16_t ReadFrSkyX()
 			FrSkyX_initialize_data(0);
 			hopping_frequency_no=0;
 			BIND_DONE;
-			state++;			
+			state++;													//FRSKY_DATA1
 			break;		
-		case FRSKY_DATA1:
-			if ( prev_option != option )
-			{
-				CC2500_WriteReg(CC2500_0C_FSCTRL0,option);				//Frequency offset hack 
-				prev_option = option ;
-			}
-			FrSkyX_set_start(hopping_frequency_no);
-			transmit=true;
-#ifdef FRSKYX_LBT
-			CC2500_Strobe(CC2500_SIDLE);
-			state++;
-			return 210;													//Wait for the freq to stabilize
-		case FRSKY_DATA2:		
-			CC2500_Strobe(CC2500_SRX);									//Acquire RSSI
-			state++;
-			return 20;
-		case FRSKY_DATA3:		
-			uint8_t rssi;
-			rssi = CC2500_ReadReg(CC2500_34_RSSI | CC2500_READ_BURST);	// 0.5 db/count, RSSI value read from the RSSI status register is a 2's complement number
-			if ((sub_protocol & 2) && rssi > 72 && rssi < 128)			//LBT and RSSI between -36 to -8.5 dBm
-			{
-				transmit=false;
-				debugln("Busy %d %d",hopping_frequency_no,rssi);
-			}
-#endif
-			CC2500_SetTxRxMode(TX_EN);
-			CC2500_SetPower();
-			CC2500_Strobe(CC2500_SFRX);
-			hopping_frequency_no = (hopping_frequency_no+FrSkyX_chanskip)%47;
-			CC2500_Strobe(CC2500_SIDLE);		
-			if(transmit)
-				CC2500_WriteData(packet, packet[0]+1);
-			state=FRSKY_DATA4;
-			return 5200;
-		case FRSKY_DATA4:
-			CC2500_SetTxRxMode(RX_EN);
-			CC2500_Strobe(CC2500_SIDLE);
-			state++;
-			return 200;
-		case FRSKY_DATA5:		
-			CC2500_Strobe(CC2500_SRX);
-			state++;
-			return 3100;
 		case FRSKY_DATA6:
 			telemetry_set_input_sync(9000);
 			len = CC2500_ReadReg(CC2500_3B_RXBYTES | CC2500_READ_BURST) & 0x7F;	
@@ -374,11 +331,52 @@ uint16_t ReadFrSkyX()
 			}
 			FrSkyX_build_packet();
 			state = FRSKY_DATA1;
-#ifdef FRSKYX_LBT
-			return 270;
-#else
+#if not defined(FRSKYX_LBT)
 			return 500;
+#endif // for LBT just continue to DATA1 right away
+		case FRSKY_DATA1:
+			if ( prev_option != option )
+			{
+				CC2500_WriteReg(CC2500_0C_FSCTRL0,option);				//Frequency offset hack 
+				prev_option = option ;
+			}
+			FrSkyX_set_start(hopping_frequency_no);
+			transmit=true;
+#ifdef FRSKYX_LBT
+			CC2500_Strobe(CC2500_SIDLE);
+			state++;
+			return 100;													//Wait for the freq to stabilize
+		case FRSKY_DATA2:		
+			CC2500_Strobe(CC2500_SRX);									//Acquire RSSI
+			state++;
+			return 400;
+		case FRSKY_DATA3:		
+			uint8_t rssi;
+			rssi = CC2500_ReadReg(CC2500_34_RSSI | CC2500_READ_BURST);	// 0.5 db/count, RSSI value read from the RSSI status register is a 2's complement number
+			if ((sub_protocol & 2) && rssi > 72 && rssi < 128)			//LBT and RSSI between -36 to -8.5 dBm
+			{
+				transmit=false;
+				debugln("Busy %d %d",hopping_frequency_no,rssi);
+			}
 #endif
+			CC2500_SetTxRxMode(TX_EN);
+			CC2500_SetPower();
+			CC2500_Strobe(CC2500_SFRX);
+			hopping_frequency_no = (hopping_frequency_no+FrSkyX_chanskip)%47;
+			CC2500_Strobe(CC2500_SIDLE);		
+			if(transmit)
+				CC2500_WriteData(packet, packet[0]+1);
+			state=FRSKY_DATA4;
+			return 5200;
+		case FRSKY_DATA4:
+			CC2500_SetTxRxMode(RX_EN);
+			CC2500_Strobe(CC2500_SIDLE);
+			state++;
+			return 200;
+		case FRSKY_DATA5:		
+			CC2500_Strobe(CC2500_SRX);
+			state++;
+			return 3100;
 	}		
 	return 1;		
 }
diff --git a/Multiprotocol/_Config.h b/Multiprotocol/_Config.h
index 7fa5ea3..443a384 100644
--- a/Multiprotocol/_Config.h
+++ b/Multiprotocol/_Config.h
@@ -224,8 +224,7 @@
 
 //FrSkyX specific setting
 //-----------------------
-//EU LBT setting
-//If commented the TX will not check if a channel is busy before transmitting
+//EU LBT setting: if commented the TX will not check if a channel is busy before transmitting.
 //#define FRSKYX_LBT
 
 //DSM specific settings
@@ -270,6 +269,8 @@
 //For er9x it depends if you have an inveter mod or not on the telemetry pin. If you don't have an inverter comment this line.
 //=>OpenTX 2.3.2 with a STM32 or OrangeRX module this setting can be ignored.
 #define INVERT_TELEMETRY
+//For STM32 and OrangeRX modules, comment to prevent the TX from forcing the serial telemetry polarity normal/invert.
+#define INVERT_TELEMETRY_TX
 
 //Uncomment if you don't want to send Multi status telemetry frames (Protocol available, Bind in progress, version...)
 //Use with er9x/erskyTX, for OpenTX MULTI_TELEMETRY below is preferred instead