From 3605109d256ef6dfd8f495ec51e2f24486483696 Mon Sep 17 00:00:00 2001
From: Bertrand Songis <bsongis@gmail.com>
Date: Mon, 19 Nov 2018 03:41:51 +0100
Subject: [PATCH] HEAD and TAIL missing in PXX2 frames

---
 radio/src/pulses/pxx2.cpp |  4 +---
 radio/src/pulses/pxx2.h   | 43 +++++++++++++++++++++++++++++++++++++--
 2 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/radio/src/pulses/pxx2.cpp b/radio/src/pulses/pxx2.cpp
index b57f052f3..2ae1adfd8 100644
--- a/radio/src/pulses/pxx2.cpp
+++ b/radio/src/pulses/pxx2.cpp
@@ -24,7 +24,6 @@
 void Pxx2Pulses::setupFrame(uint8_t port)
 {
   initFrame();
-  initCrc();
 
   static uint8_t pass[NUM_MODULES] = { MODULES_INIT(0) };
   uint8_t sendUpperChannels = 0;
@@ -55,6 +54,5 @@ void Pxx2Pulses::setupFrame(uint8_t port)
   }
 #endif
 
-  // CRC
-  addByte(crc); // TODO need to check the CRC chosen algorithm
+  endFrame();
 }
diff --git a/radio/src/pulses/pxx2.h b/radio/src/pulses/pxx2.h
index 939d0204d..1ba2bc045 100644
--- a/radio/src/pulses/pxx2.h
+++ b/radio/src/pulses/pxx2.h
@@ -41,11 +41,16 @@ class SportCrcMixin {
 };
 
 
-class Pxx2Transport: public DataBuffer<uint8_t, 64>, public SportCrcMixin {
+class Pxx2Transport: public DataBuffer<uint8_t, 64>, public PxxCrcMixin {
   protected:
     void addByte(uint8_t byte)
     {
-      SportCrcMixin::addToCrc(byte);
+      PxxCrcMixin::addToCrc(byte);
+      addByteWithoutCrc(byte);
+    };
+
+    void addByteWithoutCrc(uint8_t byte)
+    {
       *ptr++ = byte;
     }
 
@@ -63,9 +68,43 @@ class Pxx2Pulses: public PxxPulses<Pxx2Transport> {
     uint8_t data[64];
     uint8_t * ptr;
 
+    void addHead()
+    {
+      // send 7E, do not CRC
+      Pxx2Transport::addByteWithoutCrc(0x7E);
+
+      // reserve 1 byte for LEN
+      Pxx2Transport::addByteWithoutCrc(0x00);
+
+      // TYPE_C + TYPE_ID
+      Pxx2Transport::addByte(0x26); // This one is CRC-ed on purpose
+    }
+
+    void addCrc()
+    {
+      Pxx2Transport::addByteWithoutCrc(PxxCrcMixin::crc >> 8);
+      Pxx2Transport::addByteWithoutCrc(PxxCrcMixin::crc);
+    }
+
     void initFrame()
     {
+      // init the CRC counter
+      initCrc();
+
+      // reset the frame pointer
       Pxx2Transport::initBuffer();
+
+      // add the frame head
+      addHead();
+    }
+
+    void endFrame()
+    {
+      // update the frame LEN = frame length minus the 2 first bytes
+      data[1] = getSize() - 2;
+
+      // now add the CRC
+      addCrc();
     }
 };