ESP32/sdkconfig.defaults.bt

# Bluetooth A2DP Sink defaults (ESP32 Classic BT only)
# Include this in sdkconfig for boards that support Classic Bluetooth.
# These options are ignored on ESP32-S3/C3/etc which lack Classic BT.
#
# To enable: Component config → Bluetooth → then these are set automatically.

CONFIG_BT_ENABLED=y
CONFIG_BTDM_CTRL_MODE_BR_EDR_ONLY=y
CONFIG_BT_BLUEDROID_ENABLED=y
CONFIG_BT_CLASSIC_ENABLED=y
CONFIG_BT_A2DP_ENABLE=y
CONFIG_ESP_COEX_SW_COEXIST_ENABLE=y

# Security Setup
# SSP requires a screen on the device to show the code
CONFIG_BT_SSP_ENABLED=n
CONFIG_BT_PIN_CODE="05032026"


# Disable BLE host stack — A2DP uses Classic BT only.  Disabling BLE avoids
# compiling GATT server/client, SMP and L2CAP-BLE, recovering ~30-40 KB DRAM.
CONFIG_BT_BLE_ENABLED=n

# Only one A2DP connection at a time — reduce from defaults to save DRAM.
# BR/EDR ACL: 1.2 KB per connection (default 2 → 1 saves 1.2 KB)
# Bluedroid ACL: default 4 → 1
CONFIG_BTDM_CTRL_BR_EDR_MAX_ACL_CONN=1
CONFIG_BT_ACL_CONNECTIONS=1

# Allow Bluedroid to allocate from SPIRAM first, freeing internal DRAM for
# timers, DMA buffers and WiFi.  Fixes osi_alarm_new OOM crash when WiFi +
# Classic BT are both active.
CONFIG_BT_ALLOCATION_FROM_SPIRAM_FIRST=y

# Reduce WiFi buffer pressure — AirPlay is stopped while BT is streaming,
# so lower counts are safe and recover ~20 KB of internal DRAM.
CONFIG_ESP_WIFI_STATIC_RX_BUFFER_NUM=6
CONFIG_ESP_WIFI_DYNAMIC_RX_BUFFER_NUM=16
CONFIG_ESP_WIFI_DYNAMIC_TX_BUFFER_NUM=16
# RX BA window must be ≤ 2 × STATIC_RX_BUFFER_NUM
CONFIG_ESP_WIFI_RX_BA_WIN=6

# Bluedroid creates many software timers; the default queue of 10 is
# borderline.  Increase to avoid commands backing up.
CONFIG_FREERTOS_TIMER_QUEUE_LENGTH=16

# Push allocations > 1024 bytes to SPIRAM, keeping internal DRAM free for
# semaphores, DMA descriptors and WiFi management structures that *must*
# live in internal DRAM.  Default is 16384 — far too aggressive when BT
# already consumes ~100 KB of the ~320 KB budget.
CONFIG_SPIRAM_MALLOC_ALWAYSINTERNAL=1024

# Smaller TCP windows — BT/WiFi coexistence halves radio bandwidth,
# so the default 4×MSS buffers waste memory.  2×MSS is sufficient.
CONFIG_LWIP_TCP_SND_BUF_DEFAULT=2880
CONFIG_LWIP_TCP_WND_DEFAULT=2880

# Reduce IRAM usage: WiFi ISR optimisations moved to flash (saves ~12 KB)
CONFIG_ESP_WIFI_IRAM_OPT=n
CONFIG_ESP_WIFI_RX_IRAM_OPT=n

# Compiler optimization — use size optimization to reduce IRAM pressure
# (especially important when BT is enabled on ESP32)
CONFIG_COMPILER_OPTIMIZATION_SIZE=y

# Reduce IRAM usage: move non-critical code to flash
CONFIG_FREERTOS_PLACE_FUNCTIONS_INTO_FLASH=y
CONFIG_RINGBUF_PLACE_FUNCTIONS_INTO_FLASH=y
CONFIG_BTDM_CTRL_HLI=n
CONFIG_HEAP_PLACE_FUNCTION_INTO_FLASH=y