ESP32 Audio Streamer

Small ESP32 (Arduino) project that streams mono 16‑bit PCM from an I2S microphone over HTTP.

HTTP API

• GET /
  • Simple index page with an HTML5 audio player pointing to /stream.
• GET /stream
  • Audio stream of mono 16‑bit PCM at SAMPLE_RATE_HZ.
  • Content type depends on build flag STREAM_WAV_ENABLE:
    • STREAM_WAV_ENABLE=0 → audio/L16; rate=<Hz>; channels=1 (raw PCM)
    • STREAM_WAV_ENABLE=1 → audio/x-wav (WAV header followed by PCM)
• GET /uptime
  • Returns uptime information only as JSON.
  • Fields: uptime, uptime_human, days, hours, minutes, seconds
• GET /status
  • Returns device status and schedule as JSON (non-uptime fields moved from /uptime).
  • Includes both UTC and local timezone fields (local TZ set via LOCAL_TZ).
  • Fields:
    • Device/location: boot_count, location { lat, lon }, schedule_basis
    • Time: now_utc, last_ntp_check_utc; local variants: now_local, last_ntp_check_local
    • Today/tomorrow: today { civil_dawn_utc, civil_dusk_utc }, today_local { civil_dawn_local, civil_dusk_local }, and same for tomorrow/tomorrow_local
    • Mode/event: mode (day|night), next_event { type, at_utc, seconds_until }, plus next_event_local { type, at_local }
    • History: last_three_wakes_utc, next_three_sleeps_utc, and local arrays last_three_wakes_local, next_three_sleeps_local
    • Timezone info: timezone { posix }

Power Scheduling

• Awake from civil dawn → civil dusk; deep sleep at night (civil dusk → next dawn).
• Computes dawn/dusk daily using a lightweight NOAA/Meeus method (sun altitude −6°), UTC only.
• Syncs NTP at boot and at least every 24h while awake. If time is invalid, retries every 60s and defers sleep decisions until valid.
• Before deep sleep, shuts down I2S producer, ring buffer, I2S driver and Wi‑Fi.

Persistence

• RTC (retained across deep sleep): boot counter, cached dawn/dusk (today/tomorrow), last compute day (UTC YMD), last NTP sync time.
• NVS (Preferences namespace sched):
  • last_wakes (CSV of up to 3 epoch seconds) → exposed as last_three_wakes_utc
  • next_three_sleeps (CSV of up to 3 epoch seconds) → exposed as next_three_sleeps_utc

Build Flags (PlatformIO)

Add these in local_env.ini via build_flags (see local_env.ini.example). Defaults shown in parentheses.

• Wi‑Fi
  • -D WIFI_SSID="..." — Wi‑Fi SSID (required; default placeholder YOUR_SSID).
  • -D WIFI_PASS="..." — Wi‑Fi password (required; default placeholder YOUR_PASSWORD).
  • -D WIFI_TX_POWER_DBM=15 — target TX power in dBm (default 15). Mapped to closest supported step: −1, 2, 5, 7, 8.5, 11, 13, 15, 17, 18.5, 19, 19.5.
• Audio
  • -D SAMPLE_RATE_HZ=48000 — sample rate in Hz (default 48000).
  • -D CONVERT_SHIFT=11 — right shift converting 32‑bit mic to 16‑bit PCM; lower is louder, watch clipping (default 11).
  • -D HPF_ENABLE=1 — enable high‑pass/DC‑block filter (default 1=on).
  • -D HPF_CUTOFF_HZ=100 — HPF cutoff in Hz (default 100).
  • -D USE_RIGHT_CHANNEL=1 — 1: use RIGHT channel; 0: LEFT (default 1).
• I2S pins
  • -D PIN_I2S_WS=25 — WS/LRCLK pin (default 25).
  • -D PIN_I2S_SCK=33 — BCLK/SCK pin (default 33).
  • -D PIN_I2S_SD=32 — SD/DOUT pin (default 32).
  • -D I2S_PORT_NUM=0 — I2S port index (default 0).
• Stream format
  • -D STREAM_WAV_ENABLE=0 — 0: raw audio/L16, 1: audio/x-wav header (default 0).
• Location
  • -D LAT=51.4630911 — latitude in degrees (positive north). If omitted, defaults to 51.4630911.
  • -D LON=-3.1678763 — longitude in degrees (negative west). If omitted, defaults to -3.1678763.
• Buffering
  • -D CHUNK_FRAMES=1024 — producer chunk size in frames (default 1024).
  • -D RB_CAPACITY_BYTES=65536 — ring buffer size in bytes (default 65536).
  • -D DMA_BUF_COUNT_CFG=4 — I2S DMA buffer count (default 4).
• Server & logging
  • -D SERVER_PORT=80 — HTTP port (default 80).
  • -D LOG_LEVEL=2 — 1: errors, 2: info/warn/error, 3: debug (default 2).
• Local timezone
  • -D LOCAL_TZ="UTC0" — POSIX TZ string for local time (default UTC0). Examples: EST5EDT,M3.2.0/2,M11.1.0/2, CET-1CEST,M3.5.0/2,M10.5.0/3.
• Power / stability
  • -D ENABLE_BROWNOUT_DISABLE=1 — 1: disable brownout detector (workaround), 0: leave enabled (default 1).

Notes

• Set WIFI_SSID/WIFI_PASS in local_env.ini. The project logs a warning if placeholders are used.
• The stream is mono 16‑bit PCM. WAV mode adds a streaming header with unknown size fields.