diff --git a/CMakeLists.txt b/CMakeLists.txt
index d75ec18..dfe256f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -13,7 +13,8 @@ add_compile_options(
     $<$<COMPILE_LANGUAGE:CXX>:-fno-threadsafe-statics>
     $<$<COMPILE_LANGUAGE:CXX>:-fno-exceptions>
     $<$<COMPILE_LANGUAGE:CXX>:-fno-rtti>
-    $<$<CONFIG:Debug>:-fanalyzer>)
+    $<$<CONFIG:Debug>:-fanalyzer>
+    $<$<CONFIG:Debug>:-Wno-analyzer-use-of-uninitialized-value>)
 
 if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
   if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS "13")
diff --git a/src/avclan/avclan.h b/src/avclan/avclan.h
index eabd534..efcf941 100644
--- a/src/avclan/avclan.h
+++ b/src/avclan/avclan.h
@@ -99,11 +99,28 @@ enum AVCLAN_ENUM_CLASS Action : uint8_t {
   Track_Name_Resp = 0xfd,
 
   // Reports
-  Playback_Status = 0xf1,         // Typically unprompted, sent to Device::STATUS
-  Loading_Status = 0xf3, // Typically unprompted, sent to Device::STATUS
+  Playback_Status = 0xf1, // Typically unprompted, sent to Device::STATUS
+  Loading_Status = 0xf3,  // Typically unprompted, sent to Device::STATUS
   Report_TOC = 0xf9,
 };
 
+// Media functions a source device can perform (ultimately bounded by the Action
+// set above).
+enum AVCLAN_ENUM_CLASS MediaAction : uint8_t {
+  Play = 0x01,
+  Pause = 0x02,
+  Play_Pause = Play | Pause,
+  Skip_Forward,
+  Skip_Backward,
+  Track_Next,
+  Track_Prev,
+  Repeat,
+  Repeat_Single,
+  Shuffle,
+  Volume_Up,
+  Volume_Down,
+};
+
 #ifdef __cplusplus
 namespace detail {
 struct Error {
diff --git a/src/avclan/bus.cc b/src/avclan/bus.cc
index 40e12d9..a54b9a9 100644
--- a/src/avclan/bus.cc
+++ b/src/avclan/bus.cc
@@ -31,24 +31,149 @@
 
 #include "bus.hpp"
 #include "avclan.h"
-#include "avclan_phy.h" // bridge until phy has been ported
 #include "com232.h"
 #include "frame.hpp"
+#include "hal/phy.h" // bridge until phy has been ported
 
 namespace {
 constexpr int ADDR_WIDTH = 12;
 constexpr int CONTROL_WIDTH = 4;
 constexpr int BYTE_WIDTH = 8;
+
+struct trailer_bits_t {};
+struct no_parity_t : trailer_bits_t {};   // raw bits (the broadcast bit)
+struct with_parity_t : trailer_bits_t {}; // bits + parity (controller address)
+struct with_ack_t : trailer_bits_t {
+}; // bits + parity + ACK slot (all other fields)
+inline constexpr no_parity_t no_parity{};
+inline constexpr with_parity_t with_parity{};
+inline constexpr with_ack_t with_ack{};
 } // namespace
 
 namespace avclan {
 
-Bus::Handle::Handle() { AVCLAN_stopEvent(); }
-Bus::Handle::~Handle() { AVCLAN_startEvent(); }
+class Bus::Handle {
+  Handle() { phy_guard_enter(); };
+  friend Bus;
 
-void Bus::init() { AVCLAN_busInit(); };
-void Bus::mute(bool mute) { AVCLAN_muteDevice(mute); };
-bool Bus::is_muted() const { return AVCLAN_ismuted(); };
+public:
+  ~Handle() { phy_guard_leave(); };
+  Handle(const Handle &) = delete;
+  Handle(Handle &&) = delete;
+  using Error = detail::Error;
+
+  bool sendstartbit() { return phy_send_startbit(); };
+  auto readstartbit() -> Read { return phy_read_startbit(); };
+
+  template <auto N, std::unsigned_integral T,
+            std::derived_from<trailer_bits_t> Trailer>
+    requires(sizeof(T) < 3 && N < 16 && !std::same_as<Trailer, with_ack_t>)
+  Error::Send send(T bits, Trailer /*tag*/) {
+    const auto parity = sendbits<N>(bits);
+
+    if constexpr (std::is_same_v<Trailer, with_parity_t>)
+      sendbits<1>(static_cast<uint8_t>(parity));
+
+    return Send{0};
+  };
+
+  template <auto N, std::unsigned_integral T>
+    requires(sizeof(T) < 3 && N < 16)
+  Error::Send send(T bits, with_ack_t /*tag*/, bool expect_ack) {
+    send<N>(bits, with_parity);
+
+    if (expect_ack && !read_ACK())
+      return Send::NAK;
+
+    return Send{0};
+  };
+
+  template <auto N, std::unsigned_integral T,
+            std::derived_from<trailer_bits_t> Trailer>
+    requires(sizeof(T) < 3 && N < 16 && !std::same_as<Trailer, with_ack_t>)
+  Error::Read read(T *bits, Trailer /*tag*/) {
+    const auto calc_parity = readbits<N>(bits);
+    if constexpr (std::is_same_v<Trailer, with_parity_t>) {
+      uint8_t read_parity;
+      readbits<1>(&read_parity);
+      if (static_cast<uint8_t>(calc_parity) != read_parity)
+        return Read::BAD_PARITY;
+    }
+    return Read{0};
+  };
+
+  template <auto N, std::unsigned_integral T, class F>
+    requires(sizeof(T) < 3 && N < 16)
+  Error::Read read(T *bits, with_ack_t /*tag*/, F &&ack) {
+    if (read<N>(bits, with_parity) == Read::BAD_PARITY)
+      return Read::BAD_PARITY;
+
+    if (ack()) {
+      send_ACK();
+    } else {
+      uint8_t slot;
+      readbits<1>(&slot);
+    }
+
+    return Read{0};
+  };
+  template <auto N, std::unsigned_integral T>
+    requires(sizeof(T) < 3 && N < 16)
+  Error::Read read(T *bits, with_ack_t /*tag*/, bool ack) {
+    return read<N>(bits, with_ack, [=]() { return ack; });
+  }
+
+private:
+  using Read = Error::Read;
+  using Send = Error::Send;
+  using Bit = detail::Bit;
+
+  static void send_ACK() { phy_send_ack(); };
+  static uint8_t read_ACK() { return phy_read_ack(); };
+
+  template <auto N, class T> Bit sendbits(T bits);
+  template <auto N, class T> Bit readbits(T *bits);
+
+  // Temporary specializations bridging to legacy C API
+  // Replace with proper (single?) template when phy has been ported
+  template <auto N>
+    requires(N > 1 && N < 8)
+  Bit sendbits(uint8_t bits) {
+    return phy_send_bits_u8(&bits, N);
+  };
+  template <auto N>
+    requires(N <= 16)
+  Bit sendbits(uint16_t bits) {
+    return phy_send_bits_u16(&bits, N);
+  };
+  template <auto N>
+    requires(N < 8)
+  Bit readbits(uint8_t *bits) {
+    return static_cast<Bit>(phy_read_bits_u8(bits, N));
+  };
+  template <auto N>
+    requires(N <= 16)
+  Bit readbits(uint16_t *bits) {
+    return static_cast<Bit>(phy_read_bits_u16(bits, N));
+  };
+};
+
+template <> inline Bit Bus::Handle::sendbits<8>(uint8_t bits) {
+  return phy_send_byte(&bits);
+};
+template <> inline Bit Bus::Handle::sendbits<1>(uint8_t bits) {
+  const Bit bit{static_cast<Bit>(bits & 1U)};
+  phy_send_bit(bit);
+  return bit;
+};
+template <> inline Bit Bus::Handle::readbits<8>(uint8_t *bits) {
+  return static_cast<Bit>(phy_read_byte(bits));
+};
+
+void Bus::init() { phy_init(); };
+bool Bus::is_active() const { return phy_active(); };
+void Bus::mute(bool mute) { phy_mute(mute); };
+bool Bus::is_muted() const { return phy_is_muted(); };
 
 auto Bus::read(uint16_t address, Frame *in, Frame::Print print) -> Error::Read {
   struct errtype {
@@ -278,21 +403,8 @@ auto Bus::send(const Frame *out, Frame::Print print) -> Error::Send {
 
 Bus::Handle Bus::get() { return {}; };
 
-bool Bus::Handle::sendstartbit() { return AVCLAN_sendstartbit(); };
-auto Bus::Handle::readstartbit() -> Read { return AVCLAN_readstartbit(); };
-void Bus::Handle::send_ACK() { AVCLAN_sendbit_ACK(); };
-uint8_t Bus::Handle::read_ACK() { return AVCLAN_readbit_ACK(); };
-
-template <> inline Bit Bus::Handle::sendbits<8>(uint8_t bits) {
-  return AVCLAN_sendbyte(&bits);
-};
-template <> inline Bit Bus::Handle::sendbits<1>(uint8_t bits) {
-  const Bit bit{static_cast<Bit>(bits & 1U)};
-  AVCLAN_sendbit(bit);
-  return bit;
-};
-template <> inline Bit Bus::Handle::readbits<8>(uint8_t *bits) {
-  return static_cast<Bit>(AVCLAN_readbyte(bits));
-};
+#ifndef NDEBUG
+void Bus::measure() { phy_measure(); }
+#endif
 
 } // namespace avclan
diff --git a/src/avclan/bus.hpp b/src/avclan/bus.hpp
index dc4fc96..07c93eb 100644
--- a/src/avclan/bus.hpp
+++ b/src/avclan/bus.hpp
@@ -52,139 +52,30 @@
 #include <type_traits>
 
 #include "avclan.h"
-#include "avclan_phy.h" // bridge until phy has been ported
 #include "frame.hpp"
 
 namespace avclan {
 
-struct trailer_bits_t {};
-struct no_parity_t : trailer_bits_t {};   // raw bits (the broadcast bit)
-struct with_parity_t : trailer_bits_t {}; // bits + parity (controller address)
-struct with_ack_t : trailer_bits_t {
-}; // bits + parity + ACK slot (all other fields)
-inline constexpr no_parity_t no_parity{};
-inline constexpr with_parity_t with_parity{};
-inline constexpr with_ack_t with_ack{};
-
 class Bus {
 public:
-  class Handle;
   using Error = detail::Error;
 
   void init();
+
+  bool is_active() const;
   void mute(bool mute);
   bool is_muted() const;
 
+#ifndef NDEBUG
+  void measure();
+#endif
+
   Error::Read read(uint16_t address, Frame *in, Frame::Print print);
   Error::Send send(const Frame *out, Frame::Print print);
 
+private:
+  class Handle;
   static Handle get();
 };
 
-class Bus::Handle {
-  Handle();
-  friend Bus;
-
-public:
-  ~Handle();
-  Handle(const Handle &) = delete;
-  Handle(Handle &&) = delete;
-  using Error = detail::Error;
-
-  bool sendstartbit();
-  Error::Read readstartbit();
-
-  template <auto N, std::unsigned_integral T,
-            std::derived_from<trailer_bits_t> Trailer>
-    requires(sizeof(T) < 3 && N < 16 && !std::same_as<Trailer, with_ack_t>)
-  Error::Send send(T bits, Trailer /*tag*/) {
-    const auto parity = sendbits<N>(bits);
-
-    if constexpr (std::is_same_v<Trailer, with_parity_t>)
-      sendbits<1>(static_cast<uint8_t>(parity));
-
-    return Send{0};
-  };
-
-  template <auto N, std::unsigned_integral T>
-    requires(sizeof(T) < 3 && N < 16)
-  Error::Send send(T bits, with_ack_t /*tag*/, bool expect_ack) {
-    send<N>(bits, with_parity);
-
-    if (expect_ack && !read_ACK())
-      return Send::NAK;
-
-    return Send{0};
-  };
-
-  template <auto N, std::unsigned_integral T,
-            std::derived_from<trailer_bits_t> Trailer>
-    requires(sizeof(T) < 3 && N < 16 && !std::same_as<Trailer, with_ack_t>)
-  Error::Read read(T *bits, Trailer /*tag*/) {
-    const auto calc_parity = readbits<N>(bits);
-    if constexpr (std::is_same_v<Trailer, with_parity_t>) {
-      uint8_t read_parity;
-      readbits<1>(&read_parity);
-      if (static_cast<uint8_t>(calc_parity) != read_parity)
-        return Read::BAD_PARITY;
-    }
-    return Read{0};
-  };
-
-  template <auto N, std::unsigned_integral T, class F>
-    requires(sizeof(T) < 3 && N < 16)
-  Error::Read read(T *bits, with_ack_t /*tag*/, F &&ack) {
-    if (read<N>(bits, with_parity) == Read::BAD_PARITY)
-      return Read::BAD_PARITY;
-
-    if (ack()) {
-      send_ACK();
-    } else {
-      uint8_t slot;
-      readbits<1>(&slot);
-    }
-
-    return Read{0};
-  };
-  template <auto N, std::unsigned_integral T>
-    requires(sizeof(T) < 3 && N < 16)
-  Error::Read read(T *bits, with_ack_t /*tag*/, bool ack) {
-    return read<N>(bits, with_ack, [=]() { return ack; });
-  }
-
-private:
-  using Read = Error::Read;
-  using Send = Error::Send;
-  using Bit = detail::Bit;
-
-  static void send_ACK();
-  static uint8_t read_ACK();
-
-  template <auto N, class T> Bit sendbits(T bits);
-  template <auto N, class T> Bit readbits(T *bits);
-
-  // Temporary specializations bridging to legacy C API
-  // Replace with proper (single?) template when phy has been ported
-  template <auto N>
-    requires(N > 1 && N < 8)
-  Bit sendbits(uint8_t bits) {
-    return AVCLAN_sendbitsi(&bits, N);
-  };
-  template <auto N>
-    requires(N <= 16)
-  Bit sendbits(uint16_t bits) {
-    return AVCLAN_sendbitsl(&bits, N);
-  };
-  template <auto N>
-    requires(N < 8)
-  Bit readbits(uint8_t *bits) {
-    return static_cast<Bit>(AVCLAN_readbitsi(bits, N));
-  };
-  template <auto N>
-    requires(N <= 16)
-  Bit readbits(uint16_t *bits) {
-    return static_cast<Bit>(AVCLAN_readbitsl(bits, N));
-  };
-};
-
 } // namespace avclan
diff --git a/src/avclan/cdchanger.cc b/src/avclan/cdchanger.cc
index 842d6d4..3cfed57 100644
--- a/src/avclan/cdchanger.cc
+++ b/src/avclan/cdchanger.cc
@@ -10,23 +10,22 @@
 #include "cdchanger.hpp"
 #include "device.hpp"
 #include "frame.hpp"
-#include "mediacontrol.h"
-#include "statustimer.h"
+#include "hal/cd_timer.h"
+#include "hal/media.h"
 
 namespace {
 using namespace avclan;
 
-constexpr uint8_t cdloading_resp[] = {
-    to_underlying(Device::CD_CHANGER),
-    to_underlying(Device::STATUS),
-    to_underlying(Action::Loading_Status),
-    0x00,
-    0x01,
-    0x00,
-    0x01,
-    0x00,
-    0x01,
-    0x02};
+constexpr uint8_t cdloading_resp[] = {to_underlying(Device::CD_CHANGER),
+                                      to_underlying(Device::STATUS),
+                                      to_underlying(Action::Loading_Status),
+                                      0x00,
+                                      0x01,
+                                      0x00,
+                                      0x01,
+                                      0x00,
+                                      0x01,
+                                      0x02};
 
 constexpr int WIRE_SIZE = 8;  // cd state report size in bytes
 constexpr int TIME_SKIP = 15; // seconds
@@ -53,8 +52,8 @@ extern "C" bool isPlaying_callback(void *self) {
 namespace avclan {
 
 void CDChanger::init() {
-  mediacontrol_init();
-  statustimer_init(this, &incrementTime_callback, &isPlaying_callback);
+  media_init();
+  cdtimer_init(this, &incrementTime_callback, &isPlaying_callback);
 }
 
 void CDChanger::handle(const Frame *in, Frame *out) {
@@ -119,16 +118,15 @@ void CDChanger::handle(const Frame *in, Frame *out) {
     case Initial_Report_Req: {
       out->is_unicast = true;
       // No knowledge/understanding of field meaning/interpretation
-      const uint8_t cdinitreport_resp[] = {
-          0x00,
-          to_underlying(Device::CD_CHANGER),
-          to_underlying(from),
-          to_underlying(Initial_Report_Resp),
-          0x01,
-          0x31,
-          0x10,
-          0x01,
-          0x01};
+      const uint8_t cdinitreport_resp[] = {0x00,
+                                           to_underlying(Device::CD_CHANGER),
+                                           to_underlying(from),
+                                           to_underlying(Initial_Report_Resp),
+                                           0x01,
+                                           0x31,
+                                           0x10,
+                                           0x01,
+                                           0x01};
       out->length = sizeof(cdinitreport_resp);
       memcpy(out->data, cdinitreport_resp, sizeof(cdinitreport_resp));
       out->reaction = r_SendOnly;
@@ -163,7 +161,7 @@ void CDChanger::handle(const Frame *in, Frame *out) {
       secs = 0x7f;
       flags2 = 0xc0;
       generateStatus(out, true, Device::CMD_SW);
-      AVCLAN_mediaFunction(MEDIA_SKIP_FORWARD);
+      media_action(MediaAction::Track_Next);
       out->reaction = r_TrackChange;
       break;
     case Track_Seek_Down:
@@ -174,12 +172,13 @@ void CDChanger::handle(const Frame *in, Frame *out) {
           --track;
         else
           track = TWODIGIT_MAX;
+
+        media_action(MediaAction::Track_Prev);
       }
       mins = 0xff;
       secs = 0x7f;
       flags2 = 0xc0;
       generateStatus(out, true, Device::CMD_SW);
-      AVCLAN_mediaFunction(MEDIA_SKIP_BACKWARD);
       out->reaction = r_TrackChange;
       break;
     case Track_Fast_Forward: {
@@ -190,9 +189,9 @@ void CDChanger::handle(const Frame *in, Frame *out) {
         ++mins;
       }
       generateStatus(out, true, Device::CMD_SW);
-      AVCLAN_mediaFunction(MEDIA_SKIP_FORWARD);
-      statustimer_reset(); // Skipped to a whole/round sec; ensure next tick
-                           // is ~1 sec from now
+      media_action(MediaAction::Skip_Forward);
+      cdtimer_reset(); // Skipped to a whole/round sec; ensure next tick
+                       // is ~1 sec from now
       out->reaction = r_SendOnly;
       break;
     }
@@ -210,9 +209,9 @@ void CDChanger::handle(const Frame *in, Frame *out) {
       } else
         secs -= TIME_SKIP;
       generateStatus(out, true, Device::CMD_SW);
-      AVCLAN_mediaFunction(MEDIA_SKIP_BACKWARD);
-      statustimer_reset(); // Skipped to a whole/round sec; ensure next tick
-                           // is ~1 sec from now
+      media_action(MediaAction::Skip_Backward);
+      cdtimer_reset(); // Skipped to a whole/round sec; ensure next tick
+                       // is ~1 sec from now
       out->reaction = r_SendOnly;
       break;
     }
@@ -296,8 +295,8 @@ void CDChanger::react(Frame *out, detail::Error::Send err) {
       break;
     case r_TrackChange:
       setTime(0, 0);
-      statustimer_reset(); // Skipped to a whole/round sec; ensure next tick is
-                           // ~1 sec from now
+      cdtimer_reset(); // Skipped to a whole/round sec; ensure next tick is
+                       // ~1 sec from now
       [[fallthrough]];
     case r_NormalizeState:
       normalizeState();
@@ -336,8 +335,8 @@ void CDChanger::enable(Frame *out) {
   }
 }
 
-bool CDChanger::pending() { return statustimer_tickPending(); }
-void CDChanger::resolvepending() { statustimer_clearTick(); }
+bool CDChanger::pending() { return cdtimer_pending(); }
+void CDChanger::resolvepending() { cdtimer_clear(); }
 
 void CDChanger::emit(Frame *out, uint16_t peripheral) {
   out->peripheral_addr = peripheral;
@@ -352,16 +351,16 @@ bool CDChanger::isPlaying() const { return playing; }
 void CDChanger::startPlaying() {
   static bool havePlayed = false;
   if (havePlayed)
-    AVCLAN_mediaFunction(MEDIA_PLAY_PAUSE);
+    media_action(MediaAction::Play);
   havePlayed |= true;
   playing = true;
-  statustimer_reset();
+  cdtimer_reset();
 }
 
 void CDChanger::stopPlaying() {
-  statustimer_disable();
+  cdtimer_disable();
   playing = false;
-  AVCLAN_mediaFunction(MEDIA_PLAY_PAUSE);
+  media_action(MediaAction::Pause);
 }
 
 // Serialize cd_status into the wire format.
@@ -425,4 +424,10 @@ void CDChanger::normalizeState() {
   flags2 = 0x80;
 }
 
+#ifndef NDEBUG
+void CDChanger::media_action(MediaAction action) { ::media_action(action); }
+bool CDChanger::media_busy() const { return ::media_busy(); };
+void CDChanger::mic_toggle() { media_mic_toggle(); };
+#endif
+
 } // namespace avclan
diff --git a/src/avclan/cdchanger.hpp b/src/avclan/cdchanger.hpp
index e8a24f5..7abd1d7 100644
--- a/src/avclan/cdchanger.hpp
+++ b/src/avclan/cdchanger.hpp
@@ -69,6 +69,11 @@ public:
   void emit(Frame *out, uint16_t peripheral);
   void incrementTime();
   bool isPlaying() const;
+#ifndef NDEBUG
+  void media_action(MediaAction action);
+  bool media_busy() const;
+  void mic_toggle();
+#endif
 
 private:
   void startPlaying();
diff --git a/src/board.h b/src/avclan/hal/board.h
similarity index 91%
rename from src/board.h
rename to src/avclan/hal/board.h
index 1ae956e..af3a366 100644
--- a/src/board.h
+++ b/src/avclan/hal/board.h
@@ -12,7 +12,7 @@ extern "C" {
 void board_init(void);
 
 // Globally enable interrupts. Call after all peripherals are initialized.
-void board_interruptsEnable(void);
+void board_enable_interrupts(void);
 
 #ifdef __cplusplus
 }
diff --git a/src/avclan/hal/cd_timer.h b/src/avclan/hal/cd_timer.h
new file mode 100644
index 0000000..24a7f31
--- /dev/null
+++ b/src/avclan/hal/cd_timer.h
@@ -0,0 +1,32 @@
+// Copyright (C) 2026 Allen Hill <allenofthehills@gmail.com>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// CDChanger periodic-timer HAL: the ~1 Hz tick that drives the CD changer's
+// status updates. The timer hardware is target-specific; the CD changer owns
+// what a tick means (see cdchanger.cc). The device polls cdtimer_pending() and
+// clears the tick with cdtimer_clear().
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// One-time hardware bring-up. Leaves the tick disabled.
+void cdtimer_init(void *ptr, void(clbk)(void *), bool(isplay)(void *));
+
+// Reset the count so the next tick is ~1 s out, and enable the tick.
+void cdtimer_reset(void);
+
+// Restore / disable the ~1 Hz tick.
+void cdtimer_restore(void);
+void cdtimer_disable(void);
+
+extern volatile bool cdtimer_pending_flag;
+
+static inline bool cdtimer_pending() { return cdtimer_pending_flag; }
+static inline void cdtimer_clear() { cdtimer_pending_flag = false; }
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/src/avclan/hal/media.h b/src/avclan/hal/media.h
new file mode 100644
index 0000000..f68d5fd
--- /dev/null
+++ b/src/avclan/hal/media.h
@@ -0,0 +1,32 @@
+// Copyright (C) 2026 Allen Hill <allenofthehills@gmail.com>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// Media-control HAL: emulate head-unit button presses to the audio source. This
+// is device functionality (see CDChanger), so this contract is consumed only by
+// the device implementation, not the app.
+
+#pragma once
+
+#include "avclan.h"
+
+#ifdef __cplusplus
+using MediaAction = avclan::MediaAction;
+extern "C" {
+#else
+typedef enum MediaAction MediaAction;
+#endif
+
+// One-time hardware bring-up for the media driver.
+void media_init(void);
+
+// Emulate a media function (button press) on the source device.
+void media_action(MediaAction fn);
+
+#ifndef NDEBUG
+bool media_mic_toggle(void);
+bool media_busy(void);
+#endif
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/src/avclan/avclan_phy.h b/src/avclan/hal/phy.h
similarity index 58%
rename from src/avclan/avclan_phy.h
rename to src/avclan/hal/phy.h
index bf53ce6..6bdc8cf 100644
--- a/src/avclan/avclan_phy.h
+++ b/src/avclan/hal/phy.h
@@ -19,48 +19,49 @@ typedef enum Bit Bit;
 #endif
 
 // One-time bring-up of the bus hardware. Leaves the bus idle and TX unmuted.
-void AVCLAN_busInit(void);
+void phy_init(void);
 
 // Mute/unmute device TX. "Muted" means we still listen, we just don't ACK or
 // transmit.
-void AVCLAN_muteDevice(bool mute);
-bool AVCLAN_ismuted(void);
+void phy_mute(bool mute);
+bool phy_is_muted(void);
 
 // True when there is activity on the bus (something is driving it).
-bool AVCLAN_busActive(void);
+bool phy_active(void);
 
 // Bus-transaction guard: quiesce the target's other async sources around a bus
 // read/send so framing isn't disturbed, then restore them. May be a no-op on a
 // target without such contention.
-void AVCLAN_stopEvent(void);
-void AVCLAN_startEvent(void);
+void phy_guard_enter(void);
+void phy_guard_leave(void);
 
 // Start-bit handling, factored out of read/sendframe so the framing layer holds
 // no bus-timing or hardware-recovery logic.
-// - AVCLAN_readstartbit waits for and validates an incoming start bit, doing
+// - phy_read_startbit waits for and validates an incoming start bit, doing
 //   any target-specific bus recovery; see avclan::detail::Error::Read.
-// - AVCLAN_sendstartbit acquires the bus and emits a start bit; returns false
+// - phy_send_startbit acquires the bus and emits a start bit; returns false
 //   if the bus was busy.
-Read AVCLAN_readstartbit(void);
-bool AVCLAN_sendstartbit(void);
+Read phy_read_startbit(void);
+bool phy_send_startbit(void);
 
 // Per-symbol I/O. The send* helpers return the even parity of the bits sent;
-// the read* helpers return the even parity of the bits read.
-void AVCLAN_sendbit(Bit bit);
-void AVCLAN_sendbit_ACK(void);
-uint8_t AVCLAN_readbit_ACK(void);
+// the read* helpers return the even parity of the bits read. The _u8/_u16
+// suffixes name the source-operand width; `len` is how many bits (<= width).
+void phy_send_bit(Bit bit);
+void phy_send_ack(void);
+uint8_t phy_read_ack(void);
 
-Bit AVCLAN_sendbitsi(const uint8_t *bits, int8_t len);
-Bit AVCLAN_sendbitsl(const uint16_t *bits, int8_t len);
-Bit AVCLAN_sendbyte(const uint8_t *byte);
+Bit phy_send_bits_u8(const uint8_t *bits, int8_t len);
+Bit phy_send_bits_u16(const uint16_t *bits, int8_t len);
+Bit phy_send_byte(const uint8_t *byte);
 
-uint8_t AVCLAN_readbitsi(uint8_t *bits, uint8_t len);
-uint8_t AVCLAN_readbitsl(uint16_t *bits, int8_t len);
-uint8_t AVCLAN_readbyte(uint8_t *byte);
+uint8_t phy_read_bits_u8(uint8_t *bits, uint8_t len);
+uint8_t phy_read_bits_u16(uint16_t *bits, int8_t len);
+uint8_t phy_read_byte(uint8_t *byte);
 
 #ifndef NDEBUG
 // Sample and dump bus bit timing over the serial link (REPL `M`).
-void AVCLan_Measure(void);
+void phy_measure(void);
 #endif
 
 #ifdef __cplusplus
diff --git a/src/avclan/mediacontrol.h b/src/avclan/mediacontrol.h
deleted file mode 100644
index 9d2d44d..0000000
--- a/src/avclan/mediacontrol.h
+++ /dev/null
@@ -1,34 +0,0 @@
-// Copyright (C) 2026 Allen Hill <allenofthehills@gmail.com>
-// SPDX-License-Identifier: GPL-3.0-or-later
-
-// Media-control: route/handle head-unit button presses to the audio source.
-
-#pragma once
-
-#include <stdint.h>
-
-// Actions list
-typedef enum : uint8_t {
-  MEDIA_PLAY_PAUSE = 0,
-  MEDIA_SKIP_FORWARD,
-  MEDIA_SKIP_BACKWARD,
-} AVCLAN_media_fn_t;
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-// One-time hardware bring-up for the media driver.
-void mediacontrol_init();
-
-// Emulate a button press on the source device.
-void AVCLAN_mediaFunction(AVCLAN_media_fn_t fn);
-
-#ifndef NDEBUG
-bool AVCLAN_micToggle();
-bool AVCLAN_isMediaFunctioning();
-#endif
-
-#ifdef __cplusplus
-}
-#endif
diff --git a/src/avclan/peripheral.hpp b/src/avclan/peripheral.hpp
index 213147c..c52aaf7 100644
--- a/src/avclan/peripheral.hpp
+++ b/src/avclan/peripheral.hpp
@@ -25,9 +25,18 @@ public:
 
   uint16_t address() const { return address_; };
   uint16_t controller() const { return controller_; };
+  template <DeviceInterface Dev> Dev &device() {
+    return std::get<Dev>(devices_);
+  }
+
+  bool bus_is_active() const { return bus.is_active(); };
   void mute(bool mute) { bus.mute(mute); };
   bool is_muted() const { return bus.is_muted(); };
 
+#ifndef NDEBUG
+  Bus &get_bus() { return bus; }
+#endif
+
   Error::Read read(Frame *in, Frame::Print print) {
     return bus.read(address_, in, print);
   };
@@ -44,7 +53,7 @@ public:
     using enum Action;
     out->reaction = 0;
 
-    if (AVCLAN_ismuted() || in->length < 3)
+    if (is_muted() || in->length < 3)
       return;
 
     // 0xFF placeholders are variant bytes filled by writing directly to
@@ -137,6 +146,8 @@ public:
     }
   }
 
+#undef PACK3
+
   void react(Frame *out, Error::Send err) {
     if (((Devs::id == out->owning_device) || ...))
       ((Devs::id == out->owning_device
@@ -147,8 +158,6 @@ public:
       out->reaction = 0;
   }
 
-#undef PACK3
-
   template <class F> void poll_devices(F &&fun) {
     (poller(std::get<Devs>(devices_), fun), ...);
   }
diff --git a/src/avclan/statustimer.h b/src/avclan/statustimer.h
deleted file mode 100644
index 79729ea..0000000
--- a/src/avclan/statustimer.h
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright (C) 2026 Allen Hill <allenofthehills@gmail.com>
-// SPDX-License-Identifier: GPL-3.0-or-later
-
-// ~1 Hz status-update tick interface. The app
-// polls statustimer_tickPending() and clears the tick with
-// statustimer_clearTick()
-
-#pragma once
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-// One-time hardware bring-up. Leaves the tick disabled.
-void statustimer_init(void *ptr, void(clbk)(void *), bool(isplay)(void *));
-
-// Reset the count so the next tick is ~1 s out, and enable the tick.
-void statustimer_reset(void);
-
-// Enable / disable the ~1 Hz tick.
-void statustimer_restore(void);
-void statustimer_disable(void);
-
-extern volatile bool tick_pending;
-
-static inline bool statustimer_tickPending() { return tick_pending; }
-static inline void statustimer_clearTick() { tick_pending = false; }
-
-#ifdef __cplusplus
-}
-#endif
diff --git a/src/avclan/target/avr-attiny3216/CMakeLists.txt b/src/avclan/target/avr-attiny3216/CMakeLists.txt
index 89d60eb..d7262b5 100644
--- a/src/avclan/target/avr-attiny3216/CMakeLists.txt
+++ b/src/avclan/target/avr-attiny3216/CMakeLists.txt
@@ -6,7 +6,7 @@ include(FetchContent)
 target_sources(avclan PRIVATE
     phy_avr.c
     media_avr.c
-    statustick_avr.c
+    cd_timer_avr.c
     board_avr.c)
 
 target_include_directories(avclan PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
diff --git a/src/avclan/target/avr-attiny3216/board_avr.c b/src/avclan/target/avr-attiny3216/board_avr.c
index 889b303..b10211e 100644
--- a/src/avclan/target/avr-attiny3216/board_avr.c
+++ b/src/avclan/target/avr-attiny3216/board_avr.c
@@ -10,7 +10,7 @@
 #include <avr/io.h>
 #include <avr/xmega.h> // _PROTECTED_WRITE
 
-#include "board.h"
+#include "hal/board.h"
 
 void board_init(void) {
   // Main clock prescale (CLK_PRESCALE / CLK_PRESCALE_DIV come from the build).
@@ -46,4 +46,4 @@ void board_init(void) {
   PORTC.PIN1CTRL = PORT_ISC_INPUT_DISABLE_gc; // WOD
 }
 
-void board_interruptsEnable(void) { sei(); }
+void board_enable_interrupts(void) { sei(); }
diff --git a/src/avclan/target/avr-attiny3216/statustick_avr.c b/src/avclan/target/avr-attiny3216/cd_timer_avr.c
similarity index 85%
rename from src/avclan/target/avr-attiny3216/statustick_avr.c
rename to src/avclan/target/avr-attiny3216/cd_timer_avr.c
index 40f7e28..2e10a55 100644
--- a/src/avclan/target/avr-attiny3216/statustick_avr.c
+++ b/src/avclan/target/avr-attiny3216/cd_timer_avr.c
@@ -8,7 +8,7 @@
 #include <stdint.h>
 #include <util/atomic.h>
 
-#include "statustimer.h"
+#include "hal/cd_timer.h"
 
 // Measured wall-clock duration (in ms) of one nominal 32768-tick RTC period,
 // used to calibrate out the internal OSCULP32K's error. The RTC runs from
@@ -29,7 +29,7 @@ static void* changer = nullptr;
 static void (*increment)(void *) = nullptr;
 static bool (*isplaying)(void *) = nullptr;
 
-void statustimer_init(void *ptr, void (inc)(void *), bool (isplay)(void *)) {
+void cdtimer_init(void *ptr, void (inc)(void *), bool (isplay)(void *)) {
   // Setup RTC as a ~1 sec periodic timer via the normal counter's overflow.
   // Use the RTC directly (not PIT) to tune the status report interval closer to
   // 1 sec (internal osc may be slightly off)
@@ -46,7 +46,7 @@ void statustimer_init(void *ptr, void (inc)(void *), bool (isplay)(void *)) {
   isplaying = isplay;
 }
 
-void statustimer_reset() {
+void cdtimer_reset() {
   ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
     loop_until_bit_is_clear(RTC_STATUS, RTC_CNTBUSY_bp);
     RTC.CNT = 0;
@@ -55,18 +55,18 @@ void statustimer_reset() {
   }
 }
 
-void statustimer_restore() { 
+void cdtimer_restore() { 
   if (isplaying(changer))
     RTC.INTCTRL |= RTC_OVF_bm; 
 }
-void statustimer_disable() { RTC.INTCTRL &= ~RTC_OVF_bm; }
+void cdtimer_disable() { RTC.INTCTRL &= ~RTC_OVF_bm; }
 
-// Set once per overflow; consumed by the app via statustimer_tickPending().
-volatile bool tick_pending = false;
+// Set once per overflow; consumed by the app via cdtimer_pending().
+volatile bool cdtimer_pending_flag = false;
 
 // Periodic interrupt with a ~1 sec period; only enabled while playing.
 ISR(RTC_CNT_vect) {
   increment(changer);
-  tick_pending = true;
+  cdtimer_pending_flag = true;
   RTC.INTFLAGS = RTC_OVF_bm;
 }
diff --git a/src/avclan/target/avr-attiny3216/media_avr.c b/src/avclan/target/avr-attiny3216/media_avr.c
index 837e2e7..a217695 100644
--- a/src/avclan/target/avr-attiny3216/media_avr.c
+++ b/src/avclan/target/avr-attiny3216/media_avr.c
@@ -6,8 +6,8 @@
 #include <stdint.h>
 #include <util/atomic.h>
 
-#include "media_avr.h" // mediacontrol_syncDuringMask (used by the bus guard)
-#include "mediacontrol.h"
+#include "media_avr.h" // media_sync_during_mask (used by the bus guard)
+#include "hal/media.h"
 
 // F_CPU defined in timing_avr.h; the mic tick constants below are derived from
 // it (this hardware generation's TCA0/PB1 button-press implementation).
@@ -31,14 +31,14 @@ static constexpr uint16_t close_thresh =
 
 #ifndef NDEBUG
 // Toggle PB1 and return its new level.
-bool AVCLAN_micToggle() {
+bool media_mic_toggle() {
   // Take manual control of PB1 (CMP1EN gives TCA0 control of WO1/PB1 level)
   TCA0.SINGLE.CTRLB &= ~TCA_SINGLE_CMP1EN_bm;
   VPORTB.OUT ^= PIN1_bm;
   return (VPORTB.OUT & PIN1_bm) != 0;
 }
 
-bool AVCLAN_isMediaFunctioning() { return mic_ntoggles != 0; }
+bool media_busy() { return mic_ntoggles != 0; }
 #endif
 
 // Begin a press waveform of `nphases` × 100 ms level segments.
@@ -99,11 +99,21 @@ ISR(TCA0_OVF_vect) { mic_timer_isr_body(false); }
 
 // Emulate a transport-control button press on the source device. Each action
 // maps to a press-train of a given length on MIC_CONTROL.
-void AVCLAN_mediaFunction(AVCLAN_media_fn_t fn) {
-  switch (fn) {
-    case MEDIA_PLAY_PAUSE: mic_pulse(1); break;    // single press
-    case MEDIA_SKIP_FORWARD: mic_pulse(3); break;  // double-press
-    case MEDIA_SKIP_BACKWARD: mic_pulse(5); break; // triple-press
+void media_action(enum MediaAction action) {
+  switch (action) {
+    case Play:
+    case Pause:
+    case Play_Pause: mic_pulse(1); break;    // single press
+    case Skip_Forward:
+    case Track_Next: mic_pulse(3); break;  // double-press
+    case Skip_Backward:
+    case Track_Prev: mic_pulse(5); break; // triple-press
+    case Repeat:
+    case Repeat_Single:
+    case Shuffle:
+    case Volume_Up:
+    case Volume_Down:
+    default: break;
   }
 }
 
@@ -113,13 +123,13 @@ void AVCLAN_mediaFunction(AVCLAN_media_fn_t fn) {
 //  - peripheral WO1 toggles and mic_ntoggles kept in sync
 //  - maximum frame duration is ~15ms, "early" OVF remains within acceptable
 //    ranges for either high/low pulses
-// Caller (AVCLAN_stopEvent) guarantees interrupts are disabled.
-void mediacontrol_syncDuringMask() {
+// Caller (phy_guard_enter) guarantees interrupts are disabled.
+void media_sync_during_guard() {
   if (mic_ntoggles && TCA0.SINGLE.CNT >= (TCA0.SINGLE.CMP0 - close_thresh))
     mic_timer_isr_body(true);
 }
 
-void mediacontrol_init() {
+void media_init() {
   // PB1 needs to be set as an output for TCA0 to set the level
   PORTB.DIRSET = PIN1_bm;
 
diff --git a/src/avclan/target/avr-attiny3216/media_avr.h b/src/avclan/target/avr-attiny3216/media_avr.h
index 14cdebd..5c19bac 100644
--- a/src/avclan/target/avr-attiny3216/media_avr.h
+++ b/src/avclan/target/avr-attiny3216/media_avr.h
@@ -2,7 +2,7 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 // AVR-internal media-driver hooks, shared between media_avr.c and the bus
-// transaction guard (phy_avr.c's AVCLAN_stopEvent). Not part of the public
+// transaction guard (phy_avr.c's phy_guard_enter). Not part of the public
 // mediacontrol.h interface.
 
 #pragma once
@@ -13,9 +13,9 @@ extern "C" {
 
 // Keep the TCA0 press waveform roughly in sync while a bus transaction has
 // masked interrupts (runs the OVF ISR body early if an overflow is imminent).
-// MUST be called with interrupts disabled (from within AVCLAN_stopEvent's
+// MUST be called with interrupts disabled (from within phy_guard_enter's
 // ATOMIC_BLOCK).
-void mediacontrol_syncDuringMask();
+void media_sync_during_guard();
 
 #ifdef __cplusplus
 }
diff --git a/src/avclan/target/avr-attiny3216/phy_avr.c b/src/avclan/target/avr-attiny3216/phy_avr.c
index 0585c4c..4caf396 100644
--- a/src/avclan/target/avr-attiny3216/phy_avr.c
+++ b/src/avclan/target/avr-attiny3216/phy_avr.c
@@ -9,10 +9,10 @@
 #include <stdint.h>
 #include <util/atomic.h>
 
-#include "avclan_phy.h"
+#include "hal/phy.h"
 #include "com232.h"      // RS232_setRxInterrupt (guard); RS232_Print (Measure)
-#include "media_avr.h"   // mediacontrol_syncDuringMask (guard)
-#include "statustimer.h" // statustimer_enable/disable (guard)
+#include "media_avr.h"   // media_sync_during_mask (guard)
+#include "hal/cd_timer.h" // statustimer_enable/disable (guard)
 
 // F_CPU + TICK_US (timing.h) defined here; F_CPU potentially needed by
 // avr-libc.
@@ -58,15 +58,15 @@ static inline void AVCLAN_setBusDriven() {
 
 // Returns true if device TX is muted on the AVCLAN bus (both drive pins are
 // configured as inputs).
-bool AVCLAN_ismuted() {
+bool phy_is_muted() {
   return (((VPORTA_DIR & PIN4_bm) | (VPORTA_DIR & PIN0_bm)) == 0);
 }
 
 // True when the bus is being driven (i.e. not idle/floating).
-bool AVCLAN_busActive() { return !BUS_IS_IDLE; }
+bool phy_active() { return !BUS_IS_IDLE; }
 
 // Mute device TX on AVCLAN bus
-void AVCLAN_muteDevice(bool mute) {
+void phy_mute(bool mute) {
   if (mute) {
     // clang-format off
     __asm__ __volatile__("cbi %[vporta_dir], 4; \n\t" // set as INPUT (output values ignored)
@@ -99,7 +99,7 @@ static void set_AVC_logic_for(uint8_t val, uint16_t period) {
   return;
 }
 
-void AVCLAN_sendbit(Bit bit) {
+void phy_send_bit(Bit bit) {
   uint16_t zero_length, one_length;
   switch (bit) {
     case bit_zero:
@@ -120,7 +120,7 @@ void AVCLAN_sendbit(Bit bit) {
   set_AVC_logic_for(1, one_length);
 }
 
-void AVCLAN_sendbit_ACK() {
+void phy_send_ack() {
   TCB1.CNT = 0;
 
   // Wait for controller to begin ACK bit
@@ -131,7 +131,7 @@ void AVCLAN_sendbit_ACK() {
       return;
   }
 
-  AVCLAN_sendbit(bit_zero);
+  phy_send_bit(bit_zero);
 }
 
 /* Returns true if the peripheral sent an ACK bit.
@@ -139,7 +139,7 @@ void AVCLAN_sendbit_ACK() {
   sync period, and allows the receiver to drive the bus (or not) to finish a "1"
   bit.
 */
-uint8_t AVCLAN_readbit_ACK() {
+uint8_t phy_read_ack() {
   TCB1.CNT = 0;                              // Double reset of TCB1.CNT: here
   set_AVC_logic_for(0, AVCLAN_BIT1_LOGIC_0); // And here (within)
   AVCLAN_setBusIdle();                       // Stop driving bus
@@ -160,7 +160,7 @@ uint8_t AVCLAN_readbit_ACK() {
 }
 
 // Send `len` bits on the AVCLAN bus; returns the even parity
-Bit AVCLAN_sendbitsi(const uint8_t *bits, int8_t len) {
+Bit phy_send_bits_u8(const uint8_t *bits, int8_t len) {
   uint8_t b = *bits;
   uint8_t parity = 0;
   int8_t len_mod8 = 8;
@@ -175,7 +175,7 @@ Bit AVCLAN_sendbitsi(const uint8_t *bits, int8_t len) {
     for (; len_mod8 > 0; len_mod8--) {
       Bit bit = (b & 0x80) != 0;
       parity += (uint8_t)bit;
-      AVCLAN_sendbit(bit);
+      phy_send_bit(bit);
       b <<= 1;
     }
     len_mod8 = 8;
@@ -185,18 +185,18 @@ Bit AVCLAN_sendbitsi(const uint8_t *bits, int8_t len) {
 }
 
 // Send `len` bits on the AVCLAN bus; returns the even parity
-Bit AVCLAN_sendbitsl(const uint16_t *bits, int8_t len) {
-  return AVCLAN_sendbitsi((const uint8_t *)bits + 1, len);
+Bit phy_send_bits_u16(const uint16_t *bits, int8_t len) {
+  return phy_send_bits_u8((const uint8_t *)bits + 1, len);
 }
 
-Bit AVCLAN_sendbyte(const uint8_t *byte) {
+Bit phy_send_byte(const uint8_t *byte) {
   uint8_t b = *byte;
   uint8_t parity = 0;
 
   for (uint8_t nbits = 8; nbits > 0; nbits--) {
     Bit bit = (b & 0x80) != 0;
     parity += (uint8_t)bit;
-    AVCLAN_sendbit(bit);
+    phy_send_bit(bit);
     b <<= 1;
   }
   return (parity & 1);
@@ -225,7 +225,7 @@ ISR(TCB0_INT_vect) {
 }
 
 // Read `len` bits on the AVCLAN bus; returns the even parity
-uint8_t AVCLAN_readbitsi(uint8_t *bits, uint8_t len) {
+uint8_t phy_read_bits_u8(uint8_t *bits, uint8_t len) {
   cli();
   READING_BYTE = 0;
   READING_PARITY = 0;
@@ -251,20 +251,20 @@ uint8_t AVCLAN_readbitsi(uint8_t *bits, uint8_t len) {
 }
 
 // Read `len` bits on the AVCLAN bus; returns the even parity
-uint8_t AVCLAN_readbitsl(uint16_t *bits, int8_t len) {
+uint8_t phy_read_bits_u16(uint16_t *bits, int8_t len) {
   uint8_t parity = 0;
   if (len > 8) {
     uint8_t over = len - 8;
-    parity = AVCLAN_readbitsi((uint8_t *)bits + 1, over);
+    parity = phy_read_bits_u8((uint8_t *)bits + 1, over);
     len -= over;
   }
-  parity += AVCLAN_readbitsi((uint8_t *)bits + 0, len);
+  parity += phy_read_bits_u8((uint8_t *)bits + 0, len);
 
   return (parity & 1);
 }
 
 // Read a byte on the AVCLAN bus
-uint8_t AVCLAN_readbyte(uint8_t *byte) {
+uint8_t phy_read_byte(uint8_t *byte) {
   cli();
   READING_BYTE = 0;
   READING_PARITY = 0;
@@ -289,7 +289,7 @@ uint8_t AVCLAN_readbyte(uint8_t *byte) {
   return (parity & 1);
 }
 
-void AVCLAN_busInit() {
+void phy_init() {
   // Set pin 6 and 7 as input
   PORTA.DIRCLR = (PIN6_bm | PIN7_bm);
   // Disable input buffer; recommended when using AC
@@ -321,14 +321,14 @@ void AVCLAN_busInit() {
 
   AVCLAN_setBusIdle();
 
-  AVCLAN_muteDevice(false); // unmute AVCLAN bus TX
+  phy_mute(false); // unmute AVCLAN bus TX
 }
 
 // Wait for and validate an incoming start bit. On an over-long "driven" bus
 // (AC2 latched high because the bus is actually floating) this kicks PA7 hard
 // high to unlatch the comparator. The framing layer maps the result to its own
 // error reporting; no printing happens here.
-Read AVCLAN_readstartbit() {
+Read phy_read_startbit() {
   uint16_t startbitlen = TCB1.CNT = 0;
   while (!BUS_IS_IDLE) {
     startbitlen = TCB1.CNT;
@@ -370,7 +370,7 @@ Read AVCLAN_readstartbit() {
 
 // Acquire the bus and emit a start bit. Returns false if another device is
 // already driving the bus (we can't yet do proper CSMA/CD).
-bool AVCLAN_sendstartbit() {
+bool phy_send_startbit() {
   // wait for free line
   TCB1.CNT = 0;
   while (BUS_IS_IDLE) {
@@ -395,25 +395,25 @@ bool AVCLAN_sendstartbit() {
     // set_AVC_logic_for(1, AVCLAN_STARTBIT_LOGIC_1); // wait for end of start
     return false;
   }
-  AVCLAN_sendbit(bit_start);
+  phy_send_bit(bit_start);
   return true;
 }
 
 /* Disable non-read related interrupts (USART RX, RTC status tick, mic timer)
    during AVCLAN bus transactions so framing isn't disturbed. TCB0 must remain
    enabled. */
-void AVCLAN_stopEvent() {
+void phy_guard_enter() {
   ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
-    statustimer_disable();
+    cdtimer_disable();
     RS232_setRxInterrupt(false);
-    mediacontrol_syncDuringMask();
+    media_sync_during_guard();
   }
 }
 
 // Re-enable serial and periodic interrupts after a bus transaction.
-void AVCLAN_startEvent() {
+void phy_guard_leave() {
   ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
-    statustimer_restore(); // Reenable status interrupt if currently playing
+    cdtimer_restore(); // Reenable status interrupt if currently playing
     RS232_setRxInterrupt(true);
   }
 }
@@ -426,8 +426,8 @@ void AVCLAN_startEvent() {
 static uint16_t pulses[100];
 static uint16_t periods[100];
 
-void AVCLan_Measure() {
-  AVCLAN_stopEvent();
+void phy_measure() {
+  phy_guard_enter();
 
   uint8_t tmp = 0;
 
@@ -457,6 +457,6 @@ void AVCLan_Measure() {
   }
   RS232_Print("\nDone.\n");
 
-  AVCLAN_startEvent();
+  phy_guard_leave();
 }
 #endif
diff --git a/src/sniffer.cc b/src/sniffer.cc
index a0fc3d8..1a143e2 100644
--- a/src/sniffer.cc
+++ b/src/sniffer.cc
@@ -7,10 +7,10 @@
 #include <cstdint>
 #include <cstring>
 
-#include "board.h"
 #include "cdchanger.hpp"
 #include "com232.h"
 #include "frame.hpp"
+#include "hal/board.h"
 #include "peripheral.hpp"
 #include "queue.hpp"
 
@@ -76,7 +76,7 @@ int main() {
   print_help();
 
   while (true) {
-    if (AVCLAN_busActive()) {
+    if (peripheral.bus_is_active()) {
       if (auto msg = cache.pop()) {
         auto err = peripheral.read(msg.get(), Print{.print = printAllFrames,
                                                     .binary = printBinary,
@@ -171,29 +171,29 @@ int main() {
           break;
 
 #ifndef NDEBUG
-        case 'g': AVCLAN_micToggle(); break;
+        case 'g': peripheral.device<CDChanger>().mic_toggle(); break;
         case 'p':
           RS232_Print("First play/pause begin ... ");
-          AVCLAN_mediaFunction(MEDIA_PLAY_PAUSE);
-          while (AVCLAN_isMediaFunctioning()) {}
+          peripheral.device<CDChanger>().media_action(MediaAction::Play_Pause);
+          while (peripheral.device<CDChanger>().media_busy()) {}
           RS232_Print("end\nSecond play/pause begin ... ");
-          AVCLAN_mediaFunction(MEDIA_PLAY_PAUSE);
-          while (AVCLAN_isMediaFunctioning()) {}
+          peripheral.device<CDChanger>().media_action(MediaAction::Play_Pause);
+          while (peripheral.device<CDChanger>().media_busy()) {}
           RS232_Print("end\n");
           break;
         case 's':
           RS232_Print("Skip begin ... ");
-          AVCLAN_mediaFunction(MEDIA_SKIP_FORWARD);
-          while (AVCLAN_isMediaFunctioning()) {}
+          peripheral.device<CDChanger>().media_action(MediaAction::Track_Next);
+          while (peripheral.device<CDChanger>().media_busy()) {}
           RS232_Print("end\n");
           break;
         case 'b':
           RS232_Print("Skip back begin ... ");
-          AVCLAN_mediaFunction(MEDIA_SKIP_BACKWARD);
-          while (AVCLAN_isMediaFunctioning()) {}
+          peripheral.device<CDChanger>().media_action(MediaAction::Track_Prev);
+          while (peripheral.device<CDChanger>().media_busy()) {}
           RS232_Print("end\n");
           break;
-        case 'M': AVCLan_Measure(); break;
+        case 'M': peripheral.get_bus().measure(); break;
 #endif
 
         case 0x10: // Signals binary sequence incoming
@@ -290,7 +290,7 @@ namespace {
 void Setup() {
   board_init(); // clock + GPIO bring-up (target-specific)
   RS232_Init();
-  board_interruptsEnable();
+  board_enable_interrupts();
 }
 
 void print_help() {