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 (setup settling + DC offset calibration). Call once at startup.

void tile_sense_mic_sleep(tile_t *tile)

Enter low-power mode (no conversions).

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. Typically 600–900 with VDD reference, depending on supply voltage and PCB layout.

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 mic bias point. Varies with supply voltage and PCB bias circuit (typically 600–900 with VDD ref). symmetry with the rest of the driver surface).

tile

Tile handle (unused — accepted for DSL-binding

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 ≈ 5–20 counts (noise floor).

tile

Tile handle (unused — accepted for DSL-binding symmetry).

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).

tile

Tile handle (unused — accepted for DSL-binding symmetry).

samples

Sample buffer.

count

Number of samples.

dc_offset

DC bias point (use dc_level() to measure, or pass 2048).

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 CMM-2718AT sensitivity model (with the AD8605 gain divided out), and compares against `threshold_db` (0.1 dB units, e.g. 700 = 70.0 dB).

tile

Initialised tile handle.

threshold_db

SPL threshold in 0.1 dB units (e.g. 700 = 70 dB).

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 DC offset, scales to mV via the configured Vref, then maps mV→dB SPL using the CMM-2718AT's −42 dBV/Pa typical sensitivity AND the AD8605's ~48× gain (1 Pa ≈ 7.94 mV RMS at the mic → ~381 mV RMS at the ADC input, where 1 Pa SPL = 94 dB). The conversion is integer-only with a 32-entry log10 lookup table (1..32 mV). Returns dB SPL in 0.1 dB units (e.g. 700 = 70.0 dB). the noise floor. Negative values are not produced.

tile

Initialised tile handle.

Returns SPL in 0.1 dB units. Floor at 300 (~30 dB) when below

• 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.

tile

Initialised tile handle.

threshold_db

SPL threshold in 0.1 dB units.

timeout_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.

tile

Initialised tile handle.

timeout_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.)

• When switching to internal ref, allow ~10 µs for settling. This function inserts a 1 ms delay automatically.

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)

Unipolar (default) returns 0–4095 straight binary, mid-bias near 2048. Bipolar returns the same sample re-encoded as a signed 12-bit two's-complement value centred on VREF/2. Both modes use the chip's single-ended input on AIN0 — bipolar does NOT enable true differential reads (the tile does not route an opposing analog input to AIN1). It just changes how get_raw() encodes the same physical sample. After switching to bipolar, treat get_raw() output as a signed 12-bit value (sign-extend before use): see get_audio_sample() for an alternative that subtracts the calibrated DC offset.

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.