From d16756b5ef638daa3e8ef1d2d8e221fd3411b56f Mon Sep 17 00:00:00 2001
From: xssfox <xss@sprocketfox.io>
Date: Sun, 6 Jul 2025 22:07:06 +1000
Subject: [PATCH] scrambling prototype

---
 src/wenet_ldpc.c     | 10 +++++++---
 start_rx_headless.sh |  4 ++--
 tx/PacketTX.py       |  4 ++--
 tx/radio_wrappers.py | 44 +++++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 54 insertions(+), 8 deletions(-)

diff --git a/src/wenet_ldpc.c b/src/wenet_ldpc.c
index 4b3dfcc..f2305dd 100755
--- a/src/wenet_ldpc.c
+++ b/src/wenet_ldpc.c
@@ -48,6 +48,7 @@
 #include <stdint.h>
 
 #include "mpdecode_core.h"
+#include "wenet_scramble.h"
 
 /* Machine generated consts, H_rows, H_cols, test input/output data to
    change LDPC code regenerate this file. */
@@ -74,7 +75,10 @@
 /* UW pattern we look for, including start/stop bits */
 
 uint8_t uw[] = {
-    1,0,1,0,1,0,1,1,1,1,0,0,1,1,0,1,1,1,1,0,1,1,1,1,0,0,0,0,0,0,0,1
+    1,0,1,0,1,0,1,1,
+    1,1,0,0,1,1,0,1,
+    1,1,1,0,1,1,1,1,
+    0,0,0,0,0,0,0,1,
 };
 
 
@@ -200,8 +204,8 @@ int main(int argc, char *argv[]) {
         }
 
         if (state == COLLECT_PACKET) {
-            symbol_buf[ind++] = symbol;
- 
+            symbol_buf[ind] = symbol * scramble_code[ind%(sizeof(scramble_code)/sizeof(scramble_code[0]))];
+            ind++;
             if (ind == SYMBOLS_PER_PACKET) {
 
                /* now LDPC decode */
diff --git a/start_rx_headless.sh b/start_rx_headless.sh
index c20ab76..db9c71b 100755
--- a/start_rx_headless.sh
+++ b/start_rx_headless.sh
@@ -18,7 +18,7 @@ MYCALL=CHANGEME
 # Wenet Transmission Centre Frequency:
 
 # Default Wenet Frequency, as used on most Project Horus flights.
-RXFREQ=441200000
+RXFREQ=443500000
 # Secondary downlink frequency, used on dual-launch flights
 #RXFREQ=443500000
 
@@ -34,7 +34,7 @@ BIAS=0
 # building the rtl-sdr utils from this repo: https://github.com/rtlsdrblog/rtl-sdr
 
 # drs232_ldpc (traditional) or wenet_ldpc (wenet v2)
-FRAMING_MODE=drs232_ldpc
+FRAMING_MODE=wenet_ldpc
 
 # Change the following path as appropriate.
 # If running this from a .desktop file, you may need to set an absolute path here
diff --git a/tx/PacketTX.py b/tx/PacketTX.py
index 3d90a60..9003b4f 100644
--- a/tx/PacketTX.py
+++ b/tx/PacketTX.py
@@ -132,9 +132,9 @@ class PacketTX(object):
 
         if fec:
             parity = ldpc_encode(packet + crc)
-            return self.preamble + self.unique_word + packet + crc + parity
+            return self.preamble + self.unique_word + self.radio.scramble(packet + crc + parity)
         else:
-            return self.preamble + self.unique_word + packet + crc 
+            return self.preamble + self.unique_word + self.radio.scramble(packet + crc )
 
 
     def set_idle_message(self, message):
diff --git a/tx/radio_wrappers.py b/tx/radio_wrappers.py
index a8c8f1c..a8ecb76 100644
--- a/tx/radio_wrappers.py
+++ b/tx/radio_wrappers.py
@@ -140,6 +140,8 @@ class RFM98W(object):
         else:
             logging.critical("RFM98W - TX Mode not set correctly!")
 
+    def scramble(self,data):
+        return data
 
     def shutdown(self):
         """
@@ -363,6 +365,45 @@ class RFM98W_I2S(RFM98W):
             logging.error("No alsaaudio - debugging mode")
             self.pcm = BinaryDebug()
 
+# first 1000 digits of "A Million Random Digits with 100,000 Normal Deviates"
+# convert to binary by doing odd/even
+
+# a = "1009..."
+# binary_list=[]
+# for digit in a:
+#     binary_list.append (1 if int(digit) % 2 else 0)
+
+# y=0
+# byte_out=0
+# for x in binary_list:
+#     byte_out = byte_out | (x << y)
+#     y += 1
+#     if y > 7:
+#         print(hex(byte_out))
+#         byte_out=0
+#         y=0
+
+    def scramble(self,data):
+        scramble_code = [0xb9, 0x97, 0x93, 0x13, 0xf7, 0xab, 0x1e, 0x88, 0x12, 0xc4, 
+        0x28, 0x80, 0x9, 0xf8, 0xb4, 0x92, 0xfc, 0x32, 0xc6, 0xa6, 
+        0xae, 0xf7, 0x8b, 0x3a, 0xd2, 0xf1, 0xf1, 0x8a, 0x72, 0xcf, 
+        0x3d, 0xc3, 0x9e, 0x52, 0x6e, 0x7a, 0x7e, 0x37, 0xa2, 0x7, 
+        0x17, 0x71, 0x2d, 0x9d, 0x1c, 0x58, 0xc1, 0xb4, 0x65, 0xe4, 
+        0xbe, 0x5b, 0xd1, 0xf, 0xa0, 0x5a, 0x3c, 0x6f, 0xd9, 0x8, 
+        0x9c, 0x6c, 0x5c, 0x6e, 0x85, 0x94, 0xb1, 0x5d, 0xde, 0xd4, 
+        0xc3, 0x55, 0x20, 0x61, 0xd7, 0x6a, 0x81, 0x78, 0x52, 0x46, 
+        0x7c, 0x43, 0x40, 0x63, 0xf1, 0x25, 0xcb, 0xf1, 0x8c, 0xa7, 
+        0x83, 0x5c, 0xa3, 0xba, 0x5c, 0xa3, 0xc5, 0xb6, 0xf, 0x2a, 
+        0x64, 0x5f, 0xec, 0x98, 0xcf, 0xf5, 0xb6, 0x3d, 0x96, 0x42, 
+        0x16, 0x7, 0xec, 0x20, 0x32, 0x4d, 0xc6, 0x17, 0x92, 0xa6, 
+        0x91, 0xc1, 0x92, 0x43, 0x69]
+
+        out_data = b''
+        index=0
+        for x in data:
+            out_data += (x ^ scramble_code[index%len(scramble_code)]).to_bytes()
+            index+=1
+        return out_data
 
     def precompute_bytes(self):
         logging.debug("Precomputing byte lookup table")
@@ -459,7 +500,8 @@ class SerialOnly(object):
             self.serial = BinaryDebug()
             logging.info("SerialOnly - No serial port provided - using Binary Debug output (binary_debug.bin)")
 
-
+    def scramble(self,data):
+        return data
 
     def shutdown(self):
         """