Round trip packet modulation and demodulation via RRC

[m17rt] / m17core / src / decode.rs

diff --git a/m17core/src/decode.rs b/m17core/src/decode.rs
index 9fd83cdba625f9ead891b0c5a5ceb72783521ce5..911d67371cf5f5273446992cd2d472cb4ac18b47 100755 (executable)
--- a/m17core/src/decode.rs
+++ b/m17core/src/decode.rs
@@ -3,8 +3,8 @@ use crate::{
     fec::{self, p_1, p_2, p_3},
     interleave::interleave,
     protocol::{
     fec::{self, p_1, p_2, p_3},
     interleave::interleave,
     protocol::{

-        LsfFrame, PacketFrame, PacketFrameCounter, StreamFrame, BERT_SYNC, LSF_SYNC, PACKET_SYNC,
-        STREAM_SYNC,
+        LsfFrame, PacketFrame, PacketFrameCounter, StreamFrame, BERT_SYNC, END_OF_TRANSMISSION,
+        LSF_SYNC, PACKET_SYNC, PREAMBLE, STREAM_SYNC,

     },
     random::random_xor,
 };
     },
     random::random_xor,
 };


@@ -33,6 +33,8 @@ pub(crate) enum SyncBurst {
     Bert,
     Stream,
     Packet,
     Bert,
     Stream,
     Packet,

+    Preamble,
+    EndOfTransmission,

 }
 
 impl SyncBurst {
 }
 
 impl SyncBurst {


@@ -42,6 +44,8 @@ impl SyncBurst {
             Self::Bert => BERT_SYNC,
             Self::Stream => STREAM_SYNC,
             Self::Packet => PACKET_SYNC,
             Self::Bert => BERT_SYNC,
             Self::Stream => STREAM_SYNC,
             Self::Packet => PACKET_SYNC,

+            Self::Preamble => PREAMBLE,
+            Self::EndOfTransmission => END_OF_TRANSMISSION,

         }
     }
 }
         }
     }
 }


@@ -54,17 +58,18 @@ pub(crate) fn sync_burst_correlation(target: [i8; 8], samples: &[f32]) -> (f32,
     let mut pos_max: f32 = f32::MIN;
     let mut neg_max: f32 = f32::MAX;
     for i in 0..8 {
     let mut pos_max: f32 = f32::MIN;
     let mut neg_max: f32 = f32::MAX;
     for i in 0..8 {

-        pos_max = pos_max.max(samples[i * 10]);
-        neg_max = neg_max.min(samples[i * 10]);
+        pos_max = pos_max.max(samples[i]);
+        neg_max = neg_max.min(samples[i]);

     }
     let gain = (pos_max - neg_max) / 2.0;
     let shift = pos_max + neg_max;
     if gain < SYNC_MIN_GAIN {
         return (f32::MAX, gain, shift);
     }
     }
     let gain = (pos_max - neg_max) / 2.0;
     let shift = pos_max + neg_max;
     if gain < SYNC_MIN_GAIN {
         return (f32::MAX, gain, shift);
     }

+

     let mut diff = 0.0;
     for i in 0..8 {
     let mut diff = 0.0;
     for i in 0..8 {

-        let sym_diff = (((samples[i * 10] - shift) / gain) - target[i] as f32).abs();
+        let sym_diff = (((samples[i] - shift) / gain) - target[i] as f32).abs();

         if sym_diff > SYNC_BIT_THRESHOLD {
             return (f32::MAX, gain, shift);
         }
         if sym_diff > SYNC_BIT_THRESHOLD {
             return (f32::MAX, gain, shift);
         }


@@ -94,7 +99,7 @@ pub(crate) fn parse_lsf(frame: &[f32] /* length 192 */) -> Option<LsfFrame> {
         None => return None,
     };
     debug!("full lsf: {:?}", lsf.0);
         None => return None,
     };
     debug!("full lsf: {:?}", lsf.0);

-    let crc = lsf.crc();
+    let crc = lsf.check_crc();

     debug!("recv crc: {:04X}", crc);
     debug!("destination: {:?}", lsf.destination());
     debug!("source: {:?}", lsf.source());
     debug!("recv crc: {:04X}", crc);
     debug!("destination: {:?}", lsf.destination());
     debug!("source: {:?}", lsf.source());


@@ -141,8 +146,10 @@ pub(crate) fn parse_packet(frame: &[f32] /* length 192 */) -> Option<PacketFrame
         Some(packet) => packet,
         None => return None,
     };
         Some(packet) => packet,
         None => return None,
     };

-    let final_frame = (packet[25] & 0x04) > 0;
-    let number = packet[25] >> 3;
+    // TODO: the spec is inconsistent about which bit in packet[25] is EOF
+    // https://github.com/M17-Project/M17_spec/issues/147
+    let final_frame = (packet[25] & 0x80) > 0;
+    let number = (packet[25] >> 2) & 0x1f;

     let counter = if final_frame {
         PacketFrameCounter::FinalFrame {
             payload_len: number as usize,
     let counter = if final_frame {
         PacketFrameCounter::FinalFrame {
             payload_len: number as usize,