app: PAGE_AUDIO live mic meter via capture thread; ES8311 mic capture HW-verified (#6)

ES8311 ADC + on-board MEMS mic capture is HW-verified (HW-016d): a loud external
sound drives mic -> ES8311 ADC -> I2S0 RX -> DSP from the noise floor to full
scale. The long-standing "capture silent" was a weak-on-board-beep stimulus
confound, not a mic/ADC fault.

PAGE_AUDIO is now a live on-screen mic meter. A dedicated capture thread streams
one continuous full-duplex session while the page is up and publishes the
per-window peak RMS; the UI thread only reads the level and never touches I2S.
An inline per-render capture corrupted the next SPI write and wedged I2S on
hardware (HW-016e), so capture runs in its own thread, gated to the page and
enabled only after the page is painted; bar and RMS read once, shown on
separate lines.

HW-verified: live bar tracks speech ([####] rms=20680), clean header, device
responsive (no freeze observed). native_sim es8311 11/11 + audio_dsp 6/6; demo
and default blob-free builds green.

Signed-off-by: Hsiu-Chi Tsai <hctsai@linux.com>

Author: thc1006

app/src/audio.c

@@ -82,14 +82,15 @@ K_MEM_SLAB_DEFINE_STATIC(rx_slab, BLOCK_SIZE, BLOCK_COUNT, 32);
 #define LOOP_IO_TIMEOUT_MS 200
 
 /*
- * Acoustic-loopback capture (issue #6). The ES8311 ADC is mono and lands on one
- * I2S slot, so AUDIO_MIC_SLOT (a slot INDEX 0 or 1, not a channel count) picks
- * it - confirm which slot carries the ADC at HW-016. AUDIO_MIC_FULL is an
- * empirical full-scale RMS for the PAGE_AUDIO bar, tuned at HW-016 once a real
- * mic level is known.
+ * Mic capture (issue #6). The ES8311 ADC is mono and lands on one I2S slot, so
+ * AUDIO_MIC_SLOT (a slot INDEX 0 or 1, not a channel count) picks it; HW-016d
+ * confirmed slot 0 carries the ADC. AUDIO_MIC_FULL is the empirical full-scale
+ * RMS for the PAGE_AUDIO live bar: HW-016d measured quiet ~70-100, a normal
+ * voice a few hundred to a few thousand, and a loud clap >= 12000, so 2000 gives
+ * visible bars for speech without pinning the bar to 4 on every breath.
  */
 #define AUDIO_MIC_SLOT   0U
-#define AUDIO_MIC_FULL   8000U
+#define AUDIO_MIC_FULL   2000U
 #define LOOP_SIL_BLOCKS  4U
 #define LOOP_BEEP_BLOCKS 12U
 
@@ -101,7 +102,10 @@ static const struct device *const i2s_dev = DEVICE_DT_GET(DT_NODELABEL(i2s0));
 static const struct gpio_dt_spec amp_gpio =
 	GPIO_DT_SPEC_GET(DT_NODELABEL(sound_amp), amp_gpios);
 
-static bool ready;
+/* Written by audio_init() on the main thread, read by the capture thread too, so
+ * volatile (a plain bool could be cached in the capture loop and never seen set).
+ */
+static volatile bool ready;
 
 /*
  * Precomputed one-block 440 Hz mono sine, 16-bit signed, sampled at 16 kHz
@@ -348,11 +352,16 @@ void audio_beep(void)
 	audio_codec_stop_output(codec_dev);
 }
 
-/* Capture scratch + the latest loopback peak RMS (single-threaded use). */
+/* Capture scratch + the latest mic level. The capture thread (below) is the only
+ * active user of these on hardware (audio_loopback() is a dormant bring-up
+ * primitive); mic_rms_peak is WRITTEN by that thread and READ by the UI thread
+ * via audio_mic_level()/_bars(), so it is volatile (a 16-bit aligned access is
+ * atomic on this unicore SoC).
+ */
 static int16_t zero_block[BLOCK_FRAMES * AUDIO_CHANNELS];
 static int16_t rx_buf[BLOCK_FRAMES * AUDIO_CHANNELS];
 static int16_t mono_buf[BLOCK_FRAMES];
-static uint16_t mic_rms_peak;
+static volatile uint16_t mic_rms_peak;
 
 BUILD_ASSERT(sizeof(rx_buf) == BLOCK_SIZE, "rx_buf must hold exactly one I2S block");
 
@@ -516,14 +525,108 @@ void audio_loopback(void)
 	audio_codec_stop_output(codec_dev);
 }
 
+/*
+ * PAGE_AUDIO live mic meter -- a dedicated CONTINUOUS-capture thread (issue #6).
+ *
+ * While capture_on is set (the AUDIO page is up), run ONE full-duplex session and
+ * stream the ADC, updating mic_rms_peak with the peak RMS of each ~128 ms window
+ * so audio_mic_bars()/audio_mic_level() track sound LIVE and fall when quiet.
+ * This is the HW-016d-proven continuous-capture shape (one START, steady reads,
+ * one DROP) -- NOT a per-render start/stop, which corrupted the very next SPI
+ * display write and wedged I2S on hardware (HW-016e). The UI thread only READS
+ * mic_rms_peak and NEVER touches I2S, so redrawing the meter can't break the
+ * display from the UI side. Gated to the page (one START on enter, one DROP on
+ * leave -- bounded churn, like the HW-013-proven audio_loopback). Any bounded-I/O
+ * failure breaks to a DROP-only stop (skips DRAIN) so a wedged clock can't hang.
+ */
+#define CAPTURE_STACK_SIZE    3072
+#define CAPTURE_PRIORITY      7
+#define CAPTURE_WINDOW_BLOCKS 8U /* publish the level every ~128 ms */
+
+static volatile bool capture_on;
+
+void audio_capture_set(bool on)
+{
+	capture_on = on;
+}
+
+static void audio_capture_thread(void *p1, void *p2, void *p3)
+{
+	ARG_UNUSED(p1);
+	ARG_UNUSED(p2);
+	ARG_UNUSED(p3);
+
+	for (;;) {
+		uint16_t wpeak = 0U;
+		uint32_t wc = 0U;
+
+		if (!ready || !capture_on) {
+			mic_rms_peak = 0U;
+			k_msleep(50);
+			continue;
+		}
+
+		/* Start ONE full-duplex session (amp stays OFF for capture). */
+		(void)i2s_trigger(i2s_dev, I2S_DIR_BOTH, I2S_TRIGGER_DROP);
+		audio_codec_start_output(codec_dev);
+		if (loop_tx(zero_block) < 0 || loop_tx(zero_block) < 0 ||
+		    i2s_trigger(i2s_dev, I2S_DIR_BOTH, I2S_TRIGGER_START) < 0) {
+			(void)i2s_trigger(i2s_dev, I2S_DIR_BOTH, I2S_TRIGGER_DROP);
+			audio_codec_stop_output(codec_dev);
+			k_msleep(50);
+			continue;
+		}
+
+		/* Stream while still on the page. TX must keep feeding silence or
+		 * the shared clock stops and RX stalls.
+		 */
+		while (ready && capture_on) {
+			size_t size = sizeof(rx_buf);
+			size_t frames;
+			uint16_t rms;
+
+			if (loop_tx(zero_block) < 0) {
+				break;
+			}
+			if (i2s_buf_read(i2s_dev, rx_buf, &size) < 0) {
+				break;
+			}
+			if (size > sizeof(rx_buf)) {
+				size = sizeof(rx_buf);
+			}
+			frames = size / AUDIO_FRAME_BYTES;
+			audio_deinterleave(rx_buf, frames, AUDIO_MIC_SLOT, mono_buf);
+			rms = audio_rms_i16(mono_buf, frames);
+			if (rms > wpeak) {
+				wpeak = rms;
+			}
+			if (++wc >= CAPTURE_WINDOW_BLOCKS) {
+				mic_rms_peak = wpeak;
+				wpeak = 0U;
+				wc = 0U;
+			}
+		}
+
+		/* Stop: DROP only (skip DRAIN so a wedged clock can't hang), mute
+		 * the DAC, and clear the level for the next visit.
+		 */
+		(void)i2s_trigger(i2s_dev, I2S_DIR_BOTH, I2S_TRIGGER_DROP);
+		audio_codec_stop_output(codec_dev);
+		mic_rms_peak = 0U;
+	}
+}
+
+K_THREAD_DEFINE(audio_capture_tid, CAPTURE_STACK_SIZE, audio_capture_thread,
+		NULL, NULL, NULL, CAPTURE_PRIORITY, 0, 0);
+
 uint16_t audio_mic_level(void)
 {
 	return mic_rms_peak;
 }
 
-uint8_t audio_mic_bars(void)
+uint8_t audio_mic_bars(uint16_t level)
 {
-	return audio_level_bars(mic_rms_peak, AUDIO_MIC_FULL, 4U);
+	return audio_level_bars(level, AUDIO_MIC_FULL, 4U);
 }
 
 #endif /* CONFIG_APP_AUDIO */

app/src/audio.h

@@ -28,30 +28,42 @@ bool audio_ready(void);
 
 /*
  * Play a short 440 Hz tone on the speaker. The amplifier is enabled only for
- * the duration of the tone (anti-pop) and disabled again afterwards.
- *
- * The PAGE_AUDIO entry now runs audio_loopback() instead; audio_beep() is kept
- * as the standalone, HW-006-verified playback primitive (and the eventual
- * codec-sample reference) and is exercised by tests / future callers.
+ * the duration of the tone (anti-pop) and disabled again afterwards. The
+ * PAGE_AUDIO entry plays one beep as a speaker self-check; HW-006-verified.
  */
 void audio_beep(void);
 
 /*
- * Acoustic loopback self-test (issue #6): play the 440 Hz tone on the speaker
- * while capturing the on-board mic over I2S, printing per-block RMS/peak on
- * serial (the RMS rises during the beep vs the surrounding silence, so the mic
- * is verified to hear the speaker). Blocking, ~0.3 s; the amp is on only for the
- * beep phase.
+ * Acoustic loopback self-test (issue #6, bring-up primitive; not auto-run by the
+ * UI): play the 440 Hz tone while capturing the on-board mic over I2S full-duplex,
+ * printing per-block RMS/peak on serial. NOTE: at the codec's low playback volume
+ * the tiny on-board speaker is too weak to couple acoustically to the adjacent
+ * mic, so the beep phase reads ~0 - this is the weak-stimulus confound that
+ * HW-016d resolved, NOT a mic fault (a loud external sound drives the same path
+ * to full scale; see the live mic capture thread, audio_capture_set()). Blocking,
+ * ~0.3 s; amp on only for the beep phase.
  */
 void audio_loopback(void);
 
 /*
- * Peak per-block mic RMS (0..32767) from the last audio_loopback() run (0 before
- * the first run); audio_mic_bars() maps it to a 0..4 level for the PAGE_AUDIO
- * meter.
+ * Enable/disable the live mic-capture thread (issue #6). Set true while the
+ * PAGE_AUDIO page is up: a dedicated thread then runs ONE continuous full-duplex
+ * capture session and updates the level reported by audio_mic_level()/_bars()
+ * ~8x/sec, so the meter tracks sound live. Gated to the page (one start on enter,
+ * one stop on leave) so the I2S/codec only run while in use. The UI thread itself
+ * never touches I2S -- it only reads the level -- which is what keeps the SPI
+ * display stable (a per-render capture in the UI thread corrupted it; HW-016e).
+ */
+void audio_capture_set(bool on);
+
+/*
+ * The latest mic RMS (0..32767) from the capture thread (0 when the page is not
+ * up / capture is off). audio_mic_bars() maps a GIVEN level to a 0..4 bar -- pass
+ * one audio_mic_level() read to both so the bar and the printed RMS always agree
+ * (the capture thread updates the level asynchronously).
  */
 uint16_t audio_mic_level(void);
-uint8_t audio_mic_bars(void);
+uint8_t audio_mic_bars(uint16_t level);
 
 #endif /* CONFIG_APP_AUDIO */
 

app/src/main.c

@@ -127,8 +127,27 @@ int main(void)
 		struct app_status st;
 		enum app_page page = app_page_get();
 
+#ifdef CONFIG_APP_AUDIO
+		/*
+		 * Stop capture BEFORE painting a non-AUDIO page (the start is
+		 * deferred until AFTER the AUDIO page is painted, below) so a page's
+		 * first paint is never concurrent with the I2S session start/stop,
+		 * which corrupts the in-flight SPI display write (HW-016e).
+		 * Steady-state body redraws while the stream already runs are fine.
+		 */
+		if (page != PAGE_AUDIO) {
+			audio_capture_set(false);
+		}
+#endif
+
 		status_sample(&st);
 		ui_render(page, &st);
+
+#ifdef CONFIG_APP_AUDIO
+		if (page == PAGE_AUDIO) {
+			audio_capture_set(true);
+		}
+#endif
 #ifdef CONFIG_APP_BLE
 		ble_update(&st);
 #endif
@@ -229,8 +248,17 @@ int main(void)
 		       st.accel[1].val1, abs(st.accel[1].val2),
 		       st.accel[2].val1, abs(st.accel[2].val2));
 
-		/* Wake early on a button press; otherwise tick every LOOP_MS. */
-		k_sem_take(&nav_sem, K_MSEC(LOOP_MS));
+		/*
+		 * Wake early on a button press; otherwise tick every LOOP_MS, but
+		 * faster on the AUDIO page so the live mic meter updates smoothly.
+		 */
+		uint32_t tick_ms = LOOP_MS;
+#ifdef CONFIG_APP_AUDIO
+		if (page == PAGE_AUDIO) {
+			tick_ms = 250;
+		}
+#endif
+		k_sem_take(&nav_sem, K_MSEC(tick_ms));
 	}
 
 	return 0;

app/src/ui.c

@@ -208,15 +208,32 @@ static void render_ble_body(const struct app_status *s)
 static void render_audio_body(const struct app_status *s)
 {
 	char line[24];
+	char meter[6];
+	uint16_t lvl;
+	uint8_t bars;
 
 	ARG_UNUSED(s);
 
-	gfx_draw_text(MARGIN_X, body_line_y(0), HOME_FG, HOME_BG, "audio loopback");
-	gfx_draw_text(MARGIN_X, body_line_y(1), HOME_FG, HOME_BG,
-		      audio_ready() ? "enter=beep+mic" : "init failed");
-	/* Mic level from the last loopback run (bar 0..4 + raw RMS). */
-	snprintf(line, sizeof(line), "mic bar=%u rms=%u  ", audio_mic_bars(),
-		 audio_mic_level());
+	/* Read the level ONCE so the bar and the printed RMS are always from the
+	 * same sample (the capture thread updates mic_rms_peak asynchronously).
+	 */
+	lvl = audio_mic_level();
+	bars = audio_mic_bars(lvl);
+	for (uint8_t i = 0; i < 4U; i++) {
+		meter[i] = (i < bars) ? '#' : '.';
+	}
+	meter[4] = '\0';
+
+	gfx_draw_text(MARGIN_X, body_line_y(0), HOME_FG, HOME_BG,
+		      audio_ready() ? "speak now" : "init failed");
+	/*
+	 * Bar and RMS on SEPARATE lines: the 10px font fits only ~13 chars on the
+	 * 135px panel, so "[####] rms=NNNNN" clips the RMS to ~2 digits. The fixed
+	 * %-6u field clears stale digits as the level swings 1..32767.
+	 */
+	snprintf(line, sizeof(line), "[%s]", meter);
+	gfx_draw_text(MARGIN_X, body_line_y(1), HOME_FG, HOME_BG, line);
+	snprintf(line, sizeof(line), "rms=%-6u", lvl);
 	gfx_draw_text(MARGIN_X, body_line_y(2), HOME_FG, HOME_BG, line);
 }
 #endif /* CONFIG_APP_AUDIO */
@@ -369,20 +386,15 @@ void ui_render(enum app_page page, const struct app_status *s)
 		if (page_changed) {
 			gfx_clear(HOME_BG);
 			draw_header(page);
-			render_audio_body(s);
-			/*
-			 * Run the acoustic loopback on ENTER only (page-change
-			 * edge), so the nav keys KEY1/KEY2 are not hijacked. It is
-			 * blocking (~0.3 s: silence, then the 440 Hz beep with the
-			 * amp on, then silence) and prints per-block mic RMS on
-			 * serial - the RMS spikes during the beep (mic hears speaker).
-			 */
-			if (audio_ready()) {
-				audio_loopback();
-			}
-		} else {
-			render_audio_body(s);
 		}
+		/*
+		 * Live mic meter. The capture thread (enabled for this page from
+		 * main.c via audio_capture_set) streams the ADC and updates the
+		 * level; the UI only READS it here and never touches I2S, so
+		 * redrawing the bar cannot disturb the SPI display (HW-016e). The
+		 * main loop ticks faster on this page so the bar updates smoothly.
+		 */
+		render_audio_body(s);
 		break;
 #endif
 #ifdef CONFIG_APP_BLE

docs/00_RESEARCH_SNAPSHOT_UPDATED.md

@@ -31,7 +31,7 @@ All pins used in this repo's DTS were confirmed against the official PinMap:
 | IMU BMI270 | I2C 0x68, SCL G48, SDA G47 | confirmed; **runtime-verified ready** |
 | PMIC M5PM1 | I2C 0x6e, SCL G48, SDA G47 | confirmed |
 | Audio ES8311 | I2C 0x18; I2S MCLK G18, DOUT G14, BCLK G17, LRCK G15, DIN G16 | confirmed |
-| Mic (analog MEMS) | MSM381A3729H9BPC (U21) into ES8311 MIC1P/MIC1N (analog ADC input) | confirmed (schematic V0.6); capture not yet HW-verified, issue #6 / HW-016 |
+| Mic (analog MEMS) | MSM381A3729H9BPC (U21) into ES8311 MIC1P/MIC1N (analog ADC input) | confirmed (schematic V0.6); capture HW-verified (HW-016d, issue #6) |
 | Speaker amp | AW8737, gated by M5PM1 PYG3 (`sound_amp`) | confirmed; HW-006 |
 | Buttons | KEY1 G11, KEY2 G12 | confirmed |
 | IR | TX G46, RX G42 | confirmed |