feature: bt classic a2dp sink external codec api bindings

.github/configs/sdkconfig.a2dp_external_codec

@@ -0,0 +1,44 @@
+# Self-contained sdkconfig fragment for the bt_a2dp_sink_external_codec example.
+# Can be used alone (`ESP_IDF_SDKCONFIG_DEFAULTS=this_file`) OR layered
+# on top of .github/configs/sdkconfig.defaults.
+
+# Stack sizes that Rust applications generally want bumped from defaults.
+CONFIG_ESP_TIMER_TASK_STACK_SIZE=4096
+CONFIG_ESP_MAIN_TASK_STACK_SIZE=20000
+CONFIG_ESP_SYSTEM_EVENT_TASK_STACK_SIZE=8192
+CONFIG_PTHREAD_TASK_STACK_SIZE_DEFAULT=8192
+CONFIG_FREERTOS_IDLE_TASK_STACKSIZE=4096
+
+# Bluetooth Classic + Bluedroid (A2DP sink prerequisites).
+CONFIG_BT_ENABLED=y
+CONFIG_BT_BLUEDROID_ENABLED=y
+CONFIG_BT_CLASSIC_ENABLED=y
+# Disable the BLE host stack entirely. We've added a cfg gate to
+# esp-idf-svc's `bt::ble` module (src/bt.rs) so it only compiles when
+# CONFIG_BT_BLE_ENABLED=y, which sidesteps the BLE GATT bindings that
+# changed in esp-idf v6.1-dev.
+CONFIG_BT_BLE_ENABLED=n
+CONFIG_BTDM_CTRL_MODE_BR_EDR_ONLY=y
+CONFIG_BTDM_CTRL_MODE_BLE_ONLY=n
+CONFIG_BTDM_CTRL_MODE_BTDM=n
+CONFIG_BT_BTC_TASK_STACK_SIZE=15000
+
+# A2DP sink in external-codec mode with AAC + SBC SEPs.
+CONFIG_BT_A2DP_ENABLE=y
+CONFIG_BT_A2DP_USE_EXTERNAL_CODEC=y
+CONFIG_BT_A2DP_CODEC_AAC_ENABLED=y
+CONFIG_BT_A2DP_SEP_NUM_MAX=2
+
+# ESP32-WROVER (8 MB QSPI PSRAM). Bluedroid + A2DP wants more
+# heap than the bare 320 KiB internal SRAM gives.
+CONFIG_SPIRAM=y
+CONFIG_SPIRAM_MODE_QUAD=y
+CONFIG_SPIRAM_TYPE_AUTO=y
+CONFIG_SPIRAM_SPEED_80M=y
+# Flash and PSRAM share the SPI bus, so the two clock speeds must match.
+CONFIG_ESPTOOLPY_FLASHFREQ_80M=y
+CONFIG_SPIRAM_BOOT_INIT=y
+CONFIG_SPIRAM_USE_MALLOC=y
+CONFIG_SPIRAM_TRY_ALLOCATE_WIFI_LWIP=y
+CONFIG_SPIRAM_MALLOC_ALWAYSINTERNAL=16384
+CONFIG_BT_ALLOCATION_FROM_SPIRAM_FIRST=y

CHANGELOG.md

@@ -30,6 +30,7 @@ remote_component = { name = "espressif/lan87xx", version = "1.*" }
 ### Added
 - Compatibility with ESP-IDF V6.0, and some pre-release 6.0.x.
 - Added support for the Generic Ethernet PHY driver: particularly useful on ESP-IDF 6.0+ as it is built-in.
+- Added support for Bluetooth A2DP External Codec API in esp-idf v6.1 (w/ AAC codec negotiation)
 
 ## [0.52.1] - 2026-03-10
 

Cargo.toml

@@ -51,7 +51,7 @@ log = { version = "0.4", default-features = false }
 uncased = { version = "0.9.7", default-features = false }
 embedded-hal-async = { version = "1", default-features = false }
 embedded-svc = { version = "0.29", default-features = false }
-esp-idf-hal = { version = "0.46.1", default-features = false }
+esp-idf-hal = { version = "0.46.1", default-features = false, features = ["pcnt-legacy"] }
 embassy-time-driver = { version = "0.2.1", optional = true, features = ["tick-hz-1_000_000"] }
 embassy-time-queue-utils = { version = "0.3", optional = true }
 embassy-futures = "0.1.2"

espflash.toml

@@ -1 +1,2 @@
+[idf_format_args]
 partition_table = "partitions.csv"

examples/bt_a2dp_sink_external_codec.rs

@@ -0,0 +1,117 @@
+//! A2DP sink example using the external-codec API.
+//!
+//! Initialises Bluedroid classic, advertises the device as A2DP sink with
+//! both AAC and SBC stream endpoints, and logs incoming events including
+//! the encoded audio buffers delivered by the peer source (typically a
+//! phone). Decoding of those buffers is intentionally left out — pair this
+//! with Espressif's `esp_audio_codec` managed component (or any other
+//! decoder) on top.
+//!
+//! Required sdkconfig settings:
+//!
+//! ```ignore
+//! CONFIG_BT_ENABLED=y
+//! CONFIG_BT_BLUEDROID_ENABLED=y
+//! CONFIG_BT_CLASSIC_ENABLED=y
+//! CONFIG_BT_A2DP_ENABLE=y
+//! CONFIG_BT_A2DP_USE_EXTERNAL_CODEC=y
+//! CONFIG_BT_A2DP_SEP_NUM_MAX=2
+//! CONFIG_BTDM_CTRL_MODE_BR_EDR_ONLY=y
+//! CONFIG_BTDM_CTRL_MODE_BLE_ONLY=n
+//! CONFIG_BTDM_CTRL_MODE_BTDM=n
+//! CONFIG_BT_BTC_TASK_STACK_SIZE=15000
+//! ```
+//!
+//! To run this example:
+//! MCU=esp32 ESP_IDF_SDKCONFIG_DEFAULTS=.github/configs/sdkconfig.a2dp_external_codec cargo +esp espflash flash --target xtensa-esp32-espidf --example bt_a2dp_sink_external_codec --monitor
+
+#![allow(unknown_lints)]
+#![allow(unexpected_cfgs)]
+
+#[cfg(all(esp32, esp_idf_bt_a2dp_use_external_codec))]
+fn main() -> anyhow::Result<()> {
+    example::main()
+}
+
+#[cfg(not(all(esp32, esp_idf_bt_a2dp_use_external_codec)))]
+fn main() -> anyhow::Result<()> {
+    println!("FALLBACK MAIN: cfg gate did not match");
+    panic!("This example requires ESP32 with CONFIG_BT_A2DP_USE_EXTERNAL_CODEC=y");
+}
+
+#[cfg(all(esp32, esp_idf_bt_a2dp_use_external_codec))]
+mod example {
+    use std::sync::Arc;
+
+    use esp_idf_svc::bt::a2dp::{A2dpEvent, Codec, EspA2dp, Sink};
+    use esp_idf_svc::bt::gap::{DiscoveryMode, EspGap};
+    use esp_idf_svc::bt::{reduce_bt_memory, BtClassic, BtDriver};
+    use esp_idf_svc::hal::delay::FreeRtos;
+    use esp_idf_svc::hal::peripherals::Peripherals;
+    use esp_idf_svc::log::EspLogger;
+    use esp_idf_svc::nvs::EspDefaultNvsPartition;
+
+    use log::info;
+
+    pub fn main() -> anyhow::Result<()> {
+        esp_idf_svc::sys::link_patches();
+        EspLogger::initialize_default();
+        info!("step 1: logger up");
+
+        let peripherals = Peripherals::take()?;
+        info!("step 2: peripherals taken");
+        let nvs = EspDefaultNvsPartition::take()?;
+        info!("step 3: nvs taken");
+
+        let mut modem = peripherals.modem;
+
+        reduce_bt_memory(unsafe { modem.reborrow() })?;
+        info!("step 4: reduce_bt_memory ok");
+
+        let bt = Arc::new(BtDriver::<BtClassic>::new(modem, Some(nvs.clone()))?);
+        info!("step 5: BtDriver up");
+
+        let gap = EspGap::new(bt.clone())?;
+        info!("step 6: gap created");
+        gap.set_device_name("ESP32_A2DP_SINK")?;
+        gap.set_scan_mode(true, DiscoveryMode::Discoverable)?;
+        info!("step 7: gap configured");
+
+        let a2dp = EspA2dp::<'_, _, _, Sink>::new_external_codec(bt.clone())?;
+        info!("step 8: a2dp external-codec sink up");
+
+        a2dp.subscribe(|event| {
+            match &event {
+                A2dpEvent::SinkAudioData(buf) => {
+                    info!(
+                        "audio frame: {} frames, {} bytes, ts {}",
+                        buf.frames(),
+                        buf.data().len(),
+                        buf.timestamp()
+                    );
+                }
+                A2dpEvent::SinkEndpointRegistered { seid, state } => {
+                    info!("SEP {seid} register result: {state:?}");
+                }
+                A2dpEvent::AudioCodecConfigured { bd_addr, codec } => {
+                    info!("negotiated codec with {bd_addr:?}: {codec:?}");
+                }
+                other => info!("a2dp event: {other:?}"),
+            }
+            0
+        })?;
+
+        info!("step 9: subscribed; registering SEPs");
+        // AAC at seid 0 (preferred), SBC at seid 1 (mandatory fallback).
+        for (seid, codec) in [(0, Codec::aac_default()), (1, Codec::sbc_default())] {
+            info!("registering {} at seid {}", codec.name(), seid);
+            a2dp.register_sink_endpoint(seid, &codec)?;
+        }
+
+        info!("step 10: A2DP sink ready; pair with phone and play audio");
+
+        loop {
+            FreeRtos::delay_ms(10_000);
+        }
+    }
+}

src/bt.rs

@@ -24,6 +24,7 @@ extern crate alloc;
 pub mod a2dp;
 #[cfg(all(esp32, esp_idf_bt_classic_enabled, esp_idf_bt_a2dp_enable))]
 pub mod avrc;
+#[cfg(esp_idf_bt_ble_enabled)]
 pub mod ble;
 #[cfg(all(esp32, esp_idf_bt_classic_enabled))]
 pub mod gap;