typo fix

SP5WWP/include/m17/m17.h

@@ -103,6 +103,10 @@ void soft_XOR(uint16_t* out, const uint16_t* a, const uint16_t* b, const uint8_t
 extern const uint8_t rand_seq[46];
 
 void randomize_bits(uint8_t inp[SYM_PER_PLD*2]);
+void randomize_soft_bits(uint16_t inp[SYM_PER_PLD*2]);
+
+// M17 C library - lib/phy/slice.c
+void slice_symbols(uint16_t out[2*SYM_PER_PLD], const float inp[SYM_PER_PLD]);
 
 // M17 C library - lib/math/rrc.c
 //sample RRC filter for 48kHz sample rate

SP5WWP/lib/phy/interleave.c

@@ -1,5 +1,5 @@
 //-------------------------------
-// M17 C library - phy/interleave.h
+// M17 C library - phy/interleave.c
 //
 // Wojciech Kaczmarski, SP5WWP
 // M17 Project, 28 December 2023

SP5WWP/lib/phy/randomize.c

@@ -1,5 +1,5 @@
 //--------------------------------------------------------------------
-// M17 C library - phy/randomize.h
+// M17 C library - phy/randomize.c
 //
 // Wojciech Kaczmarski, SP5WWP
 // M17 Project, 29 December 2023
@@ -31,3 +31,19 @@ void randomize_bits(uint8_t inp[SYM_PER_PLD*2])
         }
     }
 }
+
+/**
+ * @brief Randomize type-4 soft bits.
+ * 
+ * @param inp Input 368 soft type-4 bits.
+ */
+void randomize_soft_bits(uint16_t inp[SYM_PER_PLD*2])
+{
+    for(uint16_t i=0; i<SYM_PER_PLD*2; i++)
+    {
+        if((rand_seq[i/8]>>(7-(i%8)))&1) //flip bit if '1'
+        {
+            inp[i]=soft_bit_NOT(inp[i]);
+        }
+    }
+}

SP5WWP/lib/phy/slice.c

@@ -0,0 +1,57 @@
+//-------------------------------
+// M17 C library - phy/slice.c
+//
+// Wojciech Kaczmarski, SP5WWP
+// M17 Project, 14 January 2024
+//-------------------------------
+
+#include <m17/m17.h>
+
+/**
+ * @brief Slice payload symbols into soft dibits.
+ * Input (RRC filtered baseband sampled at symbol centers)
+ * should be already normalized to {-3, -1, +1 +3}.
+ * @param out Soft valued dibits (type-4).
+ * @param inp Array of 184 floats (1 sample per symbol).
+ */
+void slice_symbols(uint16_t out[2*SYM_PER_PLD], const float inp[SYM_PER_PLD])
+{
+    for(uint8_t i=0; i<SYM_PER_PLD; i++)
+    {
+        //bit 0
+        if(inp[i]>=symbol_list[3])
+        {
+            out[i*2+1]=0xFFFF;
+        }
+        else if(inp[i]>=symbol_list[2])
+        {
+            out[i*2+1]=-(float)0xFFFF/(symbol_list[3]-symbol_list[2])*symbol_list[2]+inp[i]*(float)0xFFFF/(symbol_list[3]-symbol_list[2]);
+        }
+        else if(inp[i]>=symbol_list[1])
+        {
+            out[i*2+1]=0x0000;
+        }
+        else if(inp[i]>=symbol_list[0])
+        {
+            out[i*2+1]=(float)0xFFFF/(symbol_list[1]-symbol_list[0])*symbol_list[1]-inp[i]*(float)0xFFFF/(symbol_list[1]-symbol_list[0]);
+        }
+        else
+        {
+            out[i*2+1]=0xFFFF;
+        }
+
+        //bit 1
+        if(inp[i]>=symbol_list[2])
+        {
+            out[i*2]=0x0000;
+        }
+        else if(inp[i]>=symbol_list[1])
+        {
+            out[i*2]=0x7FFF-inp[i]*(float)0xFFFF/(symbol_list[2]-symbol_list[1]);
+        }
+        else
+        {
+            out[i*2]=0xFFFF;
+        }
+    }
+}

SP5WWP/m17-decoder/m17-decoder-sym.c

@@ -78,52 +78,11 @@ int main(void)
             if(pushed==SYM_PER_PLD)
             {
                 //common operations for all frame types
-                //decode symbols to soft dibits
-                for(uint8_t i=0; i<SYM_PER_PLD; i++)
-                {
-                    //bit 0
-                    if(pld[i]>=symbol_list[3])
-                    {
-                        soft_bit[i*2+1]=0xFFFF;
-                    }
-                    else if(pld[i]>=symbol_list[2])
-                    {
-                        soft_bit[i*2+1]=-(float)0xFFFF/(symbol_list[3]-symbol_list[2])*symbol_list[2]+pld[i]*(float)0xFFFF/(symbol_list[3]-symbol_list[2]);
-                    }
-                    else if(pld[i]>=symbol_list[1])
-                    {
-                        soft_bit[i*2+1]=0x0000;
-                    }
-                    else if(pld[i]>=symbol_list[0])
-                    {
-                        soft_bit[i*2+1]=(float)0xFFFF/(symbol_list[1]-symbol_list[0])*symbol_list[1]-pld[i]*(float)0xFFFF/(symbol_list[1]-symbol_list[0]);
-                    }
-                    else
-                    {
-                        soft_bit[i*2+1]=0xFFFF;
-                    }
-
-                    //bit 1
-                    if(pld[i]>=symbol_list[2])
-                    {
-                        soft_bit[i*2]=0x0000;
-                    }
-                    else if(pld[i]>=symbol_list[1])
-                    {
-                        soft_bit[i*2]=0x7FFF-pld[i]*(float)0xFFFF/(symbol_list[2]-symbol_list[1]);
-                    }
-                    else
-                    {
-                        soft_bit[i*2]=0xFFFF;
-                    }
-                }
+                //slice symbols to soft dibits
+                slice_symbols(soft_bit, pld);
 
                 //derandomize
-                for(uint16_t i=0; i<SYM_PER_PLD*2; i++)
-                {
-                    if((rand_seq[i/8]>>(7-(i%8)))&1) //soft NOT. flip soft bit if "1"
-                        soft_bit[i]=soft_bit_NOT(soft_bit[i]);
-                }
+                randomize_soft_bits(soft_bit);
 
                 //deinterleave
                 reorder_soft_bits(d_soft_bit, soft_bit);