diff --git a/src/ccsds_space_packet.gleam b/src/ccsds_space_packet.gleam
index d07cae2..eca8580 100644
--- a/src/ccsds_space_packet.gleam
+++ b/src/ccsds_space_packet.gleam
@@ -1,95 +1,26 @@
 import gleam/bool
-import gleam/int
 import gleam/io
-import gleam/string_tree
-
-pub type SpacePacketVersion {
-  VersionZero
-}
-
-pub type SpacePacketType {
-  Telemetry
-  Command
-}
-
-pub type SpacePacketSequenceFlags {
-  Continuation
-  FirstSegment
-  LastSegment
-  Unsegmented
-}
-
-pub type SpacePacketHeader {
-  SpacePacketHeader(
-    version: SpacePacketVersion,
-    sp_type: SpacePacketType,
-    sec_hdr_flag: Bool,
-    apid: Int,
-    seq_flag: SpacePacketSequenceFlags,
-    seq_count: Int,
-    packet_len: Int,
-  )
-}
-
-pub fn version_to_string(sp_version: SpacePacketVersion) -> String {
-  case sp_version {
-    VersionZero -> "v0"
-  }
-}
-
-pub fn packet_type_to_string(sp_type: SpacePacketType) -> String {
-  case sp_type {
-    Telemetry -> "Telemetry"
-    Command -> "Command"
-  }
-}
-
-pub fn seq_flag_to_string(sp_seq_flags: SpacePacketSequenceFlags) -> String {
-  case sp_seq_flags {
-    Continuation -> "Continuation"
-    FirstSegment -> "First Segment"
-    LastSegment -> "Last Segment"
-    Unsegmented -> "Unsegmented"
-  }
-}
-
-pub fn space_packet_header_to_string(sp: SpacePacketHeader) -> String {
-  string_tree.new()
-  |> string_tree.append("Version: ")
-  |> string_tree.append(version_to_string(sp.version))
-  |> string_tree.append("\n")
-  |> string_tree.append("Type: ")
-  |> string_tree.append(packet_type_to_string(sp.sp_type))
-  |> string_tree.append("\n")
-  |> string_tree.append("Secondary Header Flag: ")
-  |> string_tree.append(bool.to_string(sp.sec_hdr_flag))
-  |> string_tree.append("\n")
-  |> string_tree.append("APID: 0x")
-  |> string_tree.append(int.to_base16(sp.apid))
-  |> string_tree.append("\n")
-  |> string_tree.append("Sequence Flags: ")
-  |> string_tree.append(seq_flag_to_string(sp.seq_flag))
-  |> string_tree.append("\n")
-  |> string_tree.append("Sequence Count: ")
-  |> string_tree.append(int.to_string(sp.seq_count))
-  |> string_tree.append("\n")
-  |> string_tree.append("Packet Length: ")
-  |> string_tree.append(int.to_string(sp.packet_len))
-  |> string_tree.append("\n")
-  |> string_tree.to_string()
-}
+import gleam/result
+import space_packet/primary_hdr
 
 pub fn main() {
-  let space_packet =
-    SpacePacketHeader(
-      VersionZero,
-      Telemetry,
+  let space_packet_pri_hdr =
+    primary_hdr.PrimaryHeader(
+      0,
+      primary_hdr.Telemetry,
       False,
       0x55,
-      Unsegmented,
+      primary_hdr.Unsegmented,
       0x00,
       0x00,
     )
 
-  io.println(space_packet_header_to_string(space_packet))
+  io.println(primary_hdr.to_string(space_packet_pri_hdr))
+
+  let hdr_bin = primary_hdr.to_bit_array(space_packet_pri_hdr)
+
+  use hdr_new <- result.map(primary_hdr.from_bit_array(hdr_bin))
+
+  io.println("Is same: " <> bool.to_string(hdr_new == space_packet_pri_hdr))
+  io.println("New Header:\n" <> primary_hdr.to_string(hdr_new))
 }
diff --git a/src/space_packet/primary_hdr.gleam b/src/space_packet/primary_hdr.gleam
new file mode 100644
index 0000000..2e65b04
--- /dev/null
+++ b/src/space_packet/primary_hdr.gleam
@@ -0,0 +1,142 @@
+import gleam/bool
+import gleam/int
+import gleam/string_tree
+
+pub type PacketType {
+  Telemetry
+  Command
+}
+
+fn packet_type_from_int(val: Int) -> PacketType {
+  case val {
+    1 -> Command
+    _ -> Telemetry
+  }
+}
+
+fn packet_type_to_int(val: PacketType) -> Int {
+  case val {
+    Command -> 1
+    Telemetry -> 0
+  }
+}
+
+pub fn packet_type_to_string(sp_type: PacketType) -> String {
+  case sp_type {
+    Telemetry -> "Telemetry"
+    Command -> "Command"
+  }
+}
+
+pub type SequenceFlags {
+  Continuation
+  FirstSegment
+  LastSegment
+  Unsegmented
+}
+
+fn sequence_flags_from_int(val: Int) -> SequenceFlags {
+  case val {
+    0b00 -> Continuation
+    0b01 -> FirstSegment
+    0b10 -> LastSegment
+    _ -> Unsegmented
+  }
+}
+
+fn sequence_flags_to_int(val: SequenceFlags) -> Int {
+  case val {
+    Continuation -> 0b00
+    FirstSegment -> 0b01
+    LastSegment -> 0b10
+    Unsegmented -> 0b11
+  }
+}
+
+pub fn seq_flag_to_string(sp_seq_flags: SequenceFlags) -> String {
+  case sp_seq_flags {
+    Continuation -> "Continuation"
+    FirstSegment -> "First Segment"
+    LastSegment -> "Last Segment"
+    Unsegmented -> "Unsegmented"
+  }
+}
+
+pub type PrimaryHeader {
+  PrimaryHeader(
+    version: Int,
+    sp_type: PacketType,
+    sec_hdr_flag: Bool,
+    apid: Int,
+    seq_flag: SequenceFlags,
+    seq_count: Int,
+    packet_len: Int,
+  )
+}
+
+pub type ParseError {
+  InvalidSize
+}
+
+pub fn to_string(hdr: PrimaryHeader) -> String {
+  string_tree.new()
+  |> string_tree.append("Version: ")
+  |> string_tree.append(int.to_string(hdr.version))
+  |> string_tree.append("\n")
+  |> string_tree.append("Type: ")
+  |> string_tree.append(packet_type_to_string(hdr.sp_type))
+  |> string_tree.append("\n")
+  |> string_tree.append("Secondary Header Flag: ")
+  |> string_tree.append(bool.to_string(hdr.sec_hdr_flag))
+  |> string_tree.append("\n")
+  |> string_tree.append("APID: 0x")
+  |> string_tree.append(int.to_base16(hdr.apid))
+  |> string_tree.append("\n")
+  |> string_tree.append("Sequence Flags: ")
+  |> string_tree.append(seq_flag_to_string(hdr.seq_flag))
+  |> string_tree.append("\n")
+  |> string_tree.append("Sequence Count: ")
+  |> string_tree.append(int.to_string(hdr.seq_count))
+  |> string_tree.append("\n")
+  |> string_tree.append("Packet Length: ")
+  |> string_tree.append(int.to_string(hdr.packet_len))
+  |> string_tree.append("\n")
+  |> string_tree.to_string()
+}
+
+pub fn from_bit_array(src: BitArray) -> Result(PrimaryHeader, ParseError) {
+  case src {
+    <<
+      version:size(3),
+      sp_type:size(1),
+      sec_hdr_flag:size(1),
+      apid:size(11),
+      seq_flag:size(2),
+      seq_count:size(11),
+      packet_len:size(16),
+    >> -> {
+      Ok(PrimaryHeader(
+        version,
+        packet_type_from_int(sp_type),
+        sec_hdr_flag == 1,
+        apid,
+        sequence_flags_from_int(seq_flag),
+        seq_count,
+        packet_len,
+      ))
+    }
+    _ -> Error(InvalidSize)
+  }
+}
+
+pub fn to_bit_array(src: PrimaryHeader) -> BitArray {
+  <<
+    src.version:size(3),
+    packet_type_to_int(src.sp_type):size(1),
+    bool.to_int(src.sec_hdr_flag):size(1),
+    src.apid:size(11),
+    sequence_flags_to_int(src.seq_flag):size(2),
+    src.seq_count:size(11),
+    src.packet_len:size(16),
+  >>
+}