fix(firmware): fall detection false positives + 4MB flash support (#263, #265)

Issue #263: Default fall_thresh raised from 2.0 to 15.0 rad/s² — normal
walking produces accelerations of 2.5-5.0 which triggered constant false
"Fall Detected" alerts. Added consecutive-frame requirement (3 frames)
and 5-second cooldown debounce to prevent alert storms.

Issue #265: Added partitions_4mb.csv and sdkconfig.defaults.4mb for
ESP32-S3 boards with 4MB flash (e.g. SuperMini). OTA slots are 1.856MB
each, fitting the ~978KB firmware binary with room to spare.

Co-Authored-By: claude-flow <ruv@ruv.net>

firmware/esp32-csi-node/main/edge_processing.c

@@ -244,6 +244,10 @@ static uint32_t s_frame_count;
 /** Previous phase velocity for fall detection (acceleration). */
 static float s_prev_phase_velocity;
 
+/** Fall detection debounce state (issue #263). */
+static uint8_t  s_fall_consec_count;   /**< Consecutive frames above threshold. */
+static int64_t  s_fall_last_alert_us;  /**< Timestamp of last fall alert (debounce). */
+
 /** Adaptive calibration state. */
 static bool     s_calibrated;
 static float    s_calib_sum;
@@ -689,7 +693,7 @@ static void process_frame(const edge_ring_slot_t *slot)
     }
     s_presence_detected = (s_presence_score > threshold);
 
-    /* --- Step 10: Fall detection (phase acceleration) --- */
+    /* --- Step 10: Fall detection (phase acceleration + debounce, issue #263) --- */
     if (s_history_len >= 3) {
         uint16_t i0 = (s_history_idx + EDGE_PHASE_HISTORY_LEN - 1) % EDGE_PHASE_HISTORY_LEN;
         uint16_t i1 = (s_history_idx + EDGE_PHASE_HISTORY_LEN - 2) % EDGE_PHASE_HISTORY_LEN;
@@ -697,10 +701,26 @@ static void process_frame(const edge_ring_slot_t *slot)
         float accel = fabsf(velocity - s_prev_phase_velocity);
         s_prev_phase_velocity = velocity;
 
-        s_fall_detected = (accel > s_cfg.fall_thresh);
+        if (accel > s_cfg.fall_thresh) {
-        if (s_fall_detected) {
+            s_fall_consec_count++;
-            ESP_LOGW(TAG, "Fall detected! accel=%.4f > thresh=%.4f",
+        } else {
-                     accel, s_cfg.fall_thresh);
+            s_fall_consec_count = 0;
+        }
+
+        /* Require EDGE_FALL_CONSEC_MIN consecutive frames above threshold,
+         * plus a cooldown period to prevent alert storms. */
+        int64_t now_us = esp_timer_get_time();
+        int64_t cooldown_us = (int64_t)EDGE_FALL_COOLDOWN_MS * 1000;
+        if (s_fall_consec_count >= EDGE_FALL_CONSEC_MIN
+            && (now_us - s_fall_last_alert_us) >= cooldown_us)
+        {
+            s_fall_detected = true;
+            s_fall_last_alert_us = now_us;
+            s_fall_consec_count = 0;
+            ESP_LOGW(TAG, "Fall detected! accel=%.4f > thresh=%.4f (consec=%u)",
+                     accel, s_cfg.fall_thresh, EDGE_FALL_CONSEC_MIN);
+        } else if (s_fall_consec_count == 0) {
+            s_fall_detected = false;
         }
     }
 
@@ -850,6 +870,8 @@ esp_err_t edge_processing_init(const edge_config_t *cfg)
     s_latest_rssi = 0;
     s_frame_count = 0;
     s_prev_phase_velocity = 0.0f;
+    s_fall_consec_count = 0;
+    s_fall_last_alert_us = 0;
     s_last_vitals_send_us = 0;
     s_has_prev_iq = false;
     s_prev_iq_len = 0;

firmware/esp32-csi-node/main/edge_processing.h

@@ -42,6 +42,10 @@
 #define EDGE_CALIB_FRAMES     1200  /**< Frames for adaptive calibration (~60s at 20 Hz). */
 #define EDGE_CALIB_SIGMA_MULT 3.0f  /**< Threshold = mean + 3*sigma of ambient. */
 
+/* ---- Fall detection ---- */
+#define EDGE_FALL_COOLDOWN_MS 5000  /**< Minimum ms between fall alerts (debounce). */
+#define EDGE_FALL_CONSEC_MIN  3     /**< Consecutive frames above threshold to trigger. */
+
 /* ---- SPSC ring buffer slot ---- */
 typedef struct {
     uint8_t  iq_data[EDGE_MAX_IQ_BYTES]; /**< Raw I/Q bytes from CSI callback. */

firmware/esp32-csi-node/main/nvs_config.c

@@ -61,7 +61,7 @@ void nvs_config_load(nvs_config_t *cfg)
 #ifdef CONFIG_EDGE_FALL_THRESH
     cfg->fall_thresh = (float)CONFIG_EDGE_FALL_THRESH / 1000.0f;
 #else
-    cfg->fall_thresh = 2.0f;
+    cfg->fall_thresh = 15.0f;  /* Default raised from 2.0 — see issue #263. */
 #endif
     cfg->vital_window = 256;
 #ifdef CONFIG_EDGE_VITAL_INTERVAL_MS

firmware/esp32-csi-node/partitions_4mb.csv

@@ -0,0 +1,15 @@
+# ESP32-S3 CSI Node — 4MB flash partition table (issue #265)
+# For boards with 4MB flash (e.g. ESP32-S3 SuperMini 4MB).
+# Binary is ~978KB so each OTA slot is 1.875MB — plenty of room.
+#
+# Usage: copy to partitions_display.csv OR set in sdkconfig:
+#   CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions_4mb.csv"
+#   CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y
+#   CONFIG_ESPTOOLPY_FLASHSIZE="4MB"
+#
+# Name,      Type, SubType, Offset,   Size,      Flags
+nvs,         data, nvs,     0x9000,   0x6000,
+otadata,     data, ota,     0xF000,   0x2000,
+phy_init,    data, phy,     0x11000,  0x1000,
+ota_0,       app,  ota_0,   0x20000,  0x1D0000,
+ota_1,       app,  ota_1,   0x1F0000, 0x1D0000,

firmware/esp32-csi-node/provision.py

@@ -168,7 +168,9 @@ def main():
     parser.add_argument("--edge-tier", type=int, choices=[0, 1, 2],
                         help="Edge processing tier: 0=off, 1=stats, 2=vitals")
     parser.add_argument("--pres-thresh", type=int, help="Presence detection threshold (default: 50)")
-    parser.add_argument("--fall-thresh", type=int, help="Fall detection threshold (default: 500)")
+    parser.add_argument("--fall-thresh", type=int, help="Fall detection threshold in milli-units "
+                        "(value/1000 = rad/s²). Default: 15000 → 15.0 rad/s². "
+                        "Raise to reduce false positives in high-traffic areas.")
     parser.add_argument("--vital-win", type=int, help="Phase history window in frames (default: 300)")
     parser.add_argument("--vital-int", type=int, help="Vitals packet interval in ms (default: 1000)")
     parser.add_argument("--subk-count", type=int, help="Top-K subcarrier count (default: 32)")

firmware/esp32-csi-node/sdkconfig.defaults.4mb

@@ -0,0 +1,29 @@
+# ESP32-S3 CSI Node — 4MB Flash SDK Configuration (issue #265)
+# For boards with 4MB flash (e.g. ESP32-S3 SuperMini 4MB).
+#
+# Build: cp sdkconfig.defaults.4mb sdkconfig.defaults && idf.py set-target esp32s3 && idf.py build
+# Or:    idf.py -D SDKCONFIG_DEFAULTS="sdkconfig.defaults.4mb" set-target esp32s3 && idf.py build
+
+CONFIG_IDF_TARGET="esp32s3"
+
+# 4MB flash partition table
+CONFIG_PARTITION_TABLE_CUSTOM=y
+CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions_4mb.csv"
+CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y
+CONFIG_ESPTOOLPY_FLASHSIZE="4MB"
+
+# Compiler: optimize for size (critical for 4MB)
+CONFIG_COMPILER_OPTIMIZATION_SIZE=y
+
+# CSI support
+CONFIG_ESP_WIFI_CSI_ENABLED=y
+
+# Disable display support to save flash (ADR-045 display requires 8MB)
+# CONFIG_DISPLAY_ENABLE is not set
+
+# Reduce logging to save flash
+CONFIG_BOOTLOADER_LOG_LEVEL_WARN=y
+CONFIG_LOG_DEFAULT_LEVEL_INFO=y
+
+CONFIG_LWIP_SO_RCVBUF=y
+CONFIG_ESP_MAIN_TASK_STACK_SIZE=8192