From c52ac2cefc453b97b45f12a13c2ab1dd8af8c018 Mon Sep 17 00:00:00 2001
From: Pascal Langer <pascal_langer@yahoo.fr>
Date: Mon, 28 Jun 2021 18:04:17 +0200
Subject: [PATCH] Fix XN297Dump enhanced payload detection

---
 Multiprotocol/XN297Dump_nrf24l01.ino | 41 ++++++++++++++++------------
 Multiprotocol/XN297_EMU.ino          |  4 +--
 Multiprotocol/iface_xn297.h          |  2 +-
 3 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/Multiprotocol/XN297Dump_nrf24l01.ino b/Multiprotocol/XN297Dump_nrf24l01.ino
index 75abd88..b3207b3 100644
--- a/Multiprotocol/XN297Dump_nrf24l01.ino
+++ b/Multiprotocol/XN297Dump_nrf24l01.ino
@@ -119,29 +119,34 @@ static boolean __attribute__((unused)) XN297Dump_process_packet(void)
 	}
 
 	//Try enhanced payload
-	crc = 0xb5d2;
+	uint16_t crc_save = 0xb5d2;
 	packet_length=0;
-	for (uint8_t i = 0; i < XN297DUMP_MAX_PACKET_LEN-XN297DUMP_CRC_LENGTH; i++)
+	for (uint8_t i = 0; i < XN297DUMP_MAX_PACKET_LEN-XN297DUMP_CRC_LENGTH; i++) 
 	{
 		packet_sc[i]=packet[i]^xn297_scramble[i];
+		crc = crc_save;
 		crc16_update( packet[i], 8);
+		crc_save = crc;
 		crc16_update( packet[i+1] & 0xC0, 2);
 		crcxored=(packet[i+1]<<10)|(packet[i+2]<<2)|(packet[i+3]>>6) ;
-		if((crc ^ pgm_read_word(&xn297_crc_xorout_scrambled_enhanced[i - 3])) == crcxored)
-		{ // Found a valid CRC for the enhanced payload mode
-			packet_length=i;
-			scramble=true;
-			i++;
-			packet_sc[i]=packet[i]^xn297_scramble[i];
-			memcpy(packet_un,packet_sc,packet_length+2); // unscramble packet
-			break;
-		}
-		if((crc ^ pgm_read_word(&xn297_crc_xorout_enhanced[i - 3])) == crcxored)
-		{ // Found a valid CRC for the enhanced payload mode
-			packet_length=i;
-			scramble=false;
-			memcpy(packet_un,packet,packet_length+2); 	// packet is unscrambled
-			break;
+		if(i>=3)
+		{
+			if((crc ^ pgm_read_word(&xn297_crc_xorout_scrambled_enhanced[i - 3])) == crcxored)
+			{ // Found a valid CRC for the enhanced payload mode
+				packet_length=i;
+				scramble=true;
+				i++;
+				packet_sc[i]=packet[i]^xn297_scramble[i];
+				memcpy(packet_un,packet_sc,packet_length+2); // unscramble packet
+				break;
+			}
+			if((crc ^ pgm_read_word(&xn297_crc_xorout_enhanced[i - 3])) == crcxored)
+			{ // Found a valid CRC for the enhanced payload mode
+				packet_length=i;
+				scramble=false;
+				memcpy(packet_un,packet,packet_length+2); 	// packet is unscrambled
+				break;
+			}
 		}
 	}
 	if(packet_length!=0)
@@ -324,7 +329,7 @@ static uint16_t XN297Dump_callback()
 								switch(bitrate)
 								{
 									case XN297DUMP_250K:
-										XN297_Configure(XN297_CRCEN, scramble?XN297_SCRAMBLED:XN297_UNSCRAMBLED, XN297_250K);
+										XN297_Configure(XN297_CRCEN, scramble?XN297_SCRAMBLED:XN297_UNSCRAMBLED, XN297_250K, true);
 										debug("250K");
 										break;
 									case XN297DUMP_2M:
diff --git a/Multiprotocol/XN297_EMU.ino b/Multiprotocol/XN297_EMU.ino
index a487b7c..000d8af 100644
--- a/Multiprotocol/XN297_EMU.ino
+++ b/Multiprotocol/XN297_EMU.ino
@@ -53,7 +53,7 @@ const uint16_t xn297_crc_xorout_enhanced[] = {
     0xABFC, 0xE68E, 0x0DE7, 0x28A2, 0x1965 };
 #endif
 
-static bool __attribute__((unused)) XN297_Configure(bool crc_en, bool scramble_en, bool bitrate)
+static bool __attribute__((unused)) XN297_Configure(bool crc_en, bool scramble_en, bool bitrate, bool force_nrf)
 {
 	xn297_crc = crc_en;
 	xn297_scramble_enabled = scramble_en;
@@ -61,7 +61,7 @@ static bool __attribute__((unused)) XN297_Configure(bool crc_en, bool scramble_e
 	xn297_rf = XN297_NRF;
 	
 	#if defined(NRF24L01_INSTALLED) and defined(CC2500_INSTALLED)
-		if(bitrate == XN297_1M)
+		if(bitrate == XN297_1M || force_nrf)
 			xn297_rf = XN297_NRF;		// Use NRF24L01
 		else
 			xn297_rf = XN297_CC2500;	// Use CC2500
diff --git a/Multiprotocol/iface_xn297.h b/Multiprotocol/iface_xn297.h
index bd50122..4d65e1a 100644
--- a/Multiprotocol/iface_xn297.h
+++ b/Multiprotocol/iface_xn297.h
@@ -23,7 +23,7 @@
 
 //////////////
 // Functions
-static bool __attribute__((unused)) XN297_Configure(bool, bool, bool);
+static bool __attribute__((unused)) XN297_Configure(bool, bool, bool, bool force_nrf=false);
 static void __attribute__((unused)) XN297_SetTXAddr(const uint8_t*, uint8_t);
 static void __attribute__((unused)) XN297_SetRXAddr(const uint8_t*, uint8_t);
 static void __attribute__((unused)) XN297_SetTxRxMode(enum TXRX_State);