From 8876aae2cc979ab82e785952ae39409c5c87166b Mon Sep 17 00:00:00 2001
From: David Given <dg@cowlark.com>
Date: Tue, 30 Apr 2024 23:09:30 +0200
Subject: [PATCH] Calculate gaps in bits, not bytes (more accurate). Pad the
 end of the track to avoid weirdness reading the last sector.

---
 arch/tartu/encoder.cc  | 15 +++++++--------
 arch/tartu/tartu.proto |  3 ---
 2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/tartu/encoder.cc b/arch/tartu/encoder.cc
index fa1b1963..ba8b1c35 100644
--- a/arch/tartu/encoder.cc
+++ b/arch/tartu/encoder.cc
@@ -28,18 +28,19 @@ public:
         _bits.resize(bitsPerRevolution);
         _cursor = 0;
 
-        writeFillerRawBytesUs(_config.gap1_us());
+        writeFillerRawBitsUs(_config.gap1_us());
         bool first = true;
         for (const auto& sectorData : sectors)
         {
             if (!first)
-                writeFillerRawBytesUs(_config.gap4_us());
+                writeFillerRawBitsUs(_config.gap4_us());
             first = false;
             writeSector(sectorData);
         }
 
         if (_cursor > _bits.size())
             error("track data overrun");
+        writeFillerRawBitsUs(_config.target_rotational_period_ms() * 1000.0);
 
         std::unique_ptr<Fluxmap> fluxmap(new Fluxmap);
         fluxmap->appendBits(_bits,
@@ -67,13 +68,11 @@ private:
         }
     }
 
-    void writeFillerRawBytesUs(double us)
+    void writeFillerRawBitsUs(double us)
     {
-        uint16_t byte = _config.gap_fill_byte();
-        unsigned count = (us / _clockRateUs) / 16;
-        fmt::print("count={}\n", count);
+        unsigned count = (us / _clockRateUs) / 2;
         for (int i = 0; i < count; i++)
-            writeRawBits(byte, 16);
+            writeRawBits(0b10, 2);
     };
 
     void writeSector(const std::shared_ptr<const Sector>& sectorData)
@@ -90,7 +89,7 @@ private:
             writeBytes(bytes);
         }
 
-        writeFillerRawBytesUs(_config.gap3_us());
+        writeFillerRawBitsUs(_config.gap3_us());
         writeRawBits(_config.data_marker(), 64);
         {
             Bytes bytes;
diff --git a/arch/tartu/tartu.proto b/arch/tartu/tartu.proto
index 522202bf..dc906c02 100644
--- a/arch/tartu/tartu.proto
+++ b/arch/tartu/tartu.proto
@@ -24,7 +24,4 @@ message TartuEncoderProto {
     optional uint64 data_marker = 7
         [ default = 0xaaaaaaaa44895545,
           (help) = "64-bit raw bit pattern of data record marker" ];
-    optional uint32 gap_fill_byte = 8
-        [ default = 0xaaaa,
-          (help) = "16-bit raw bit pattern of fill byte" ];
 }