Sense.MIC

uint8_t tile_sense_mic_find(tiles_pal_t *hal, uint8_t instance)

Lightweight probe — does not configure the device. The MAX11645 has no WHO_AM_I register; this checks for an ACK at 0x36.

void tile_sense_mic_init(tiles_pal_t *hal, uint8_t instance, tile_t *tile, const sense_mic_cfg_t *cfg)

Sends setup byte (reference, clock, polarity) and configuration byte (scan mode, channel, single-ended). Verifies the device responds by performing a test read. Pass cfg=NULL for defaults: VDD reference, AIN0 (mic), single-ended, unipolar, internal clock, single-channel scan.

• Blocks for ~5 ms (~15 ms with the internal reference, which takes 10 ms to wake). Call once at startup.

void tile_sense_mic_sleep(tile_t *tile)

The ADC powers down between conversions on its own; sleep also turns an internal reference off (~330 µA). The mic and amp run from V+ and keep drawing ~1.2 mA: the tile has no switch for them.

void tile_sense_mic_wake(tile_t *tile)

Wake from sleep, restore previous configuration.

void tile_sense_mic_reset(tile_t *tile)

Reset the config register to power-on defaults. Must call init() again.

uint16_t tile_sense_mic_get_vref_mv(tile_t *tile)

Returns the Vref used for millivolt conversions (3300 for VDD, 2048 for internal, or the user-specified value for external).

uint16_t tile_sense_mic_get_raw(tile_t *tile)

The MAX11645 auto-converts on every read — no trigger needed. Conversion time is ~3.5 µs (internal clock); the I2C transaction itself dominates the timing (~55 µs at 400 kHz).

uint16_t tile_sense_mic_get_raw_mv(tile_t *tile)

Conversion: mv = raw * vref_mv / 4096

int16_t tile_sense_mic_get_audio_sample(tile_t *tile)

Returns: (raw - dc_offset) where dc_offset is auto-calibrated during init(). Useful for audio waveform capture where DC bias is removed.

Returns Signed 16-bit value. 0 = silence.

uint16_t tile_sense_mic_get_dc_offset(tile_t *tile)

Measured during init() by averaging 64 samples. Near 0 on this board (the amp rests at 0 V; see the header), a few counts of amp offset.

void tile_sense_mic_get_samples(tile_t *tile, uint16_t *buf, uint16_t count)

Reads are back-to-back; effective sample rate depends on I2C bus speed: - 400 kHz: ~12.5 ksps - 1 MHz: ~16 ksps

buf

Output buffer (caller-allocated, min count entries)

count

Number of samples to read

uint16_t tile_sense_mic_dc_level(tile_t *tile, const uint16_t *samples, uint16_t count)

Useful for determining the resting level (near 0 on this board).

samples

Sample buffer (typically from get_samples()).

count

Number of samples in the buffer.

Returns DC offset in raw ADC counts.

uint16_t tile_sense_mic_peak_to_peak(tile_t *tile, const uint16_t *samples, uint16_t count)

Returns max - min across all samples. Silence is a few counts. On this board only the positive half of the signal is captured, so this is the positive peak, not the full swing.

samples

Sample buffer.

count

Number of samples.

Returns Peak-to-peak amplitude in raw ADC counts.

uint16_t tile_sense_mic_rms(tile_t *tile, const uint16_t *samples, uint16_t count, uint16_t dc_offset)

Compute RMS amplitude relative to a DC offset (raw counts).

samples

Sample buffer.

count

Number of samples.

dc_offset

Resting level (get_dc_offset(), or dc_level() of a quiet buffer).

Returns RMS of AC component in raw ADC counts.

uint16_t tile_sense_mic_amplitude_mv(tile_t *tile, uint16_t pp_raw)

Uses the configured reference voltage to scale a peak-to-peak raw ADC count into millivolts: mv = pp_raw * vref_mv / 4096.

pp_raw

[0..4095] Peak-to-peak amplitude in raw ADC counts.

Returns Amplitude in millivolts.

uint8_t tile_sense_mic_is_loud(tile_t *tile, int16_t threshold_db)

Captures a short sample buffer (~64 samples / ~5 ms at 12.5 ksps) via @ref tile_sense_mic_get_samples, computes the RMS amplitude relative to the calibrated DC offset, converts it to dB SPL via the signal-chain model above, and compares against `threshold_db` (0.1 dB units, e.g. 700 = 70.0 dB).

threshold_db

[300..1100] SPL threshold in 0.1 dB units (e.g. 700 = 70 dB). Readings start at ~45 dB and clip near 112 dB, so thresholds outside that never change.

Returns 1 if measured SPL > threshold, 0 otherwise.

• Blocking. Takes ~5 ms while sampling.

int16_t tile_sense_mic_read_spl_db(tile_t *tile)

Captures a short sample buffer (~64 samples), computes the RMS amplitude relative to the calibrated resting level, scales it to 0.1 mV via the configured Vref, then maps to dB SPL: −38 dBV/Pa (1 Pa = 94 dB = 12.59 mV RMS at the mic, ~302 mV RMS at the ADC after the 24x chain), +3 dB for the half-wave signal. Integer-only, with a 32-entry log10 table. Returns dB SPL in 0.1 dB units (e.g. 700 = 70.0 dB). measurement floor. Negative values are not produced.

Returns SPL in 0.1 dB units. 300 (30.0 dB) when below the ~45 dB

• Blocking. Takes ~5 ms while sampling.
• Accuracy regime documented in the section comment above.

uint8_t tile_sense_mic_wait_for_sound(tile_t *tile, int16_t threshold_db, uint32_t timeout_ms)

Polls @ref tile_sense_mic_read_spl_db every ~5 ms until the computed SPL (in 0.1 dB units) exceeds `threshold_db`, or the elapsed time exceeds `timeout_ms`. Useful for "wake on sound" patterns — e.g., wait for a door slam, then fire an action.

threshold_db

[300..1100] SPL threshold in 0.1 dB units.

timeout_ms

[1..60000] ms Maximum wait, in milliseconds.

Returns 1 if threshold was crossed, 0 on timeout.

• Blocking until threshold or timeout.

uint8_t tile_sense_mic_detect_clap(tile_t *tile, uint32_t timeout_ms)

Watches the SPL stream looking for the canonical clap signature: 1. Quiet bracket (≥100 ms below ~50 dB SPL) — establishes baseline 2. First peak (>~70 dB SPL spike, <50 ms wide) 3. Quiet gap (50–500 ms below threshold) 4. Second peak (>~70 dB SPL spike, <50 ms wide) 5. Quiet bracket (≥100 ms below threshold) — ensures it's really a clap-clap Thresholds are integer-fixed: peak ≈ 700 (70.0 dB), quiet floor ≈ 500 (50.0 dB). The pattern detector samples SPL every ~5 ms.

timeout_ms

[1..60000] ms Maximum wait, in milliseconds.

Returns 1 if a clap pattern was detected, 0 on timeout.

• Blocking until pattern detected or timeout. False positives on door knocks / drawer slams are expected — this is a coarse pattern detector, not a trained classifier.

void tile_sense_mic_set_reference(tile_t *tile, sense_mic_ref_t ref)

Change the reference voltage source.

ref

One of the sense_mic_ref_t values (VDD, INTERNAL, etc.)

• The internal reference takes 10 ms to wake; this function waits for it. Don't select REF_INTERNAL_BUF or REF_EXTERNAL on this tile (see sense_mic_ref_t). Call calibrate() afterwards: the resting level in counts changes with the reference.

void tile_sense_mic_set_channel(tile_t *tile, sense_mic_channel_t ch)

Change the active ADC channel.

ch

SENSE_MIC_CH_AIN0 (mic) or SENSE_MIC_CH_AIN1

void tile_sense_mic_set_scan_mode(tile_t *tile, sense_mic_scan_t scan)

Change the scan mode.

scan

SENSE_MIC_SCAN_SINGLE, SENSE_MIC_SCAN_UP, or SENSE_MIC_SCAN_8X

void tile_sense_mic_set_clock_mode(tile_t *tile, sense_mic_clock_t clk)

Selects whether the MAX11645 clocks conversions from its internal 2.8 MHz oscillator (default) or from the I2C SCL line. In external-clock mode, conversion timing is locked to the host I2C bus, which makes it possible to synchronise multiple Sense.MIC tiles or to align ADC sampling with another time-base.

clk

SENSE_MIC_CLOCK_INTERNAL or SENSE_MIC_CLOCK_EXTERNAL

• External-clock mode only takes effect during the next read transaction; SCL must remain active for the full conversion window or the result will be invalid.

void tile_sense_mic_set_polarity(tile_t *tile, sense_mic_polarity_t pol)

No effect on this tile: bipolar coding applies only to differential inputs, and the driver always converts single-ended (AIN1 is not connected). get_raw() stays 0-4095 straight binary either way. Kept for API compatibility. For signed audio use get_audio_sample(), which subtracts the calibrated resting level.

pol

SENSE_MIC_POLARITY_UNIPOLAR or SENSE_MIC_POLARITY_BIPOLAR

void tile_sense_mic_calibrate(tile_t *tile)

Averages 64 samples to update the stored bias point.

• Call in a quiet environment for best results.