ADR-110: ESP32-C6 firmware extension (#764)

Closes the firmware-side ADR-110 design at v0.7.0-esp32 after a 38-iter /loop SOTA sprint.

Headline (bench, COM9+COM12 ESP32-C6):
- 99.56% cross-board RX, 104.1 µs smoothed offset stdev (≤100 µs §2.4 target met)
- 3.95× EMA suppression, 1.4 ppm crystal skew preserved

4 firmware releases: v0.6.7 / v0.6.8 / v0.6.9 / v0.7.0-esp32.
42 ADR-110 unit tests, 1761 v2 workspace tests, full Firmware CI + QEMU green.

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

@@ -33,6 +33,11 @@
 #include "swarm_bridge.h"
 #include "rv_radio_ops.h"          /* ADR-081 Layer 1 — Radio Abstraction Layer. */
 #include "adaptive_controller.h"   /* ADR-081 Layer 2 — Adaptive controller. */
+#include "c6_twt.h"                /* ADR-110: TWT (no-op stub on S3) */
+#include "c6_timesync.h"           /* ADR-110: 802.15.4 mesh time-sync (no-op on S3) */
+#include "c6_lp_core.h"            /* ADR-110: LP-core hibernation (no-op on S3) */
+#include "c6_sync_espnow.h"        /* ADR-110 D1 workaround: ESP-NOW sync */
+#include "c6_softap_he.h"          /* ADR-110 B1/B2: HE/TWT soft-AP (no-op when disabled) */
 #ifdef CONFIG_CSI_MOCK_ENABLED
 #include "mock_csi.h"
 #endif
@@ -112,6 +117,17 @@ static void wifi_init_sta(void)
 
     ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
     ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &wifi_config));
+
+#if defined(CONFIG_IDF_TARGET_ESP32C6) && defined(CONFIG_C6_SOFTAP_HE_ENABLE)
+    /* ADR-110 B1/B2 cheap-unblock: bring up a soft-AP that advertises HE +
+     * TWT Responder=1 so a second C6 board can negotiate iTWT against
+     * this node. c6_softap_he_start() switches the mode to AP+STA. */
+    uint8_t softap_chan = 0;
+    if (c6_softap_he_start(&softap_chan) == ESP_OK) {
+        ESP_LOGI(TAG, "C6 soft-AP HE armed on channel %u (ADR-110 B1/B2)", softap_chan);
+    }
+#endif
+
     ESP_ERROR_CHECK(esp_wifi_start());
 
     ESP_LOGI(TAG, "WiFi STA initialized, connecting to SSID: %s", g_nvs_config.wifi_ssid);
@@ -147,13 +163,27 @@ void app_main(void)
     csi_collector_set_node_id(g_nvs_config.node_id);
 
     const esp_app_desc_t *app_desc = esp_app_get_description();
-    ESP_LOGI(TAG, "ESP32-S3 CSI Node (ADR-018) — v%s — Node ID: %d",
-             app_desc->version, g_nvs_config.node_id);
+#if defined(CONFIG_IDF_TARGET_ESP32C6)
+    const char *target_name = "ESP32-C6";
+#elif defined(CONFIG_IDF_TARGET_ESP32S3)
+    const char *target_name = "ESP32-S3";
+#else
+    const char *target_name = "ESP32";
+#endif
+    ESP_LOGI(TAG, "%s CSI Node (ADR-018 / ADR-110) — v%s — Node ID: %d",
+             target_name, app_desc->version, g_nvs_config.node_id);
 
-    /* Turn off onboard WS2812 LED on GPIO 38 */
+    /* Turn off onboard WS2812 LED.
+     * S3 dev boards put the LED on GPIO 38; C6 dev boards on GPIO 8.
+     * On C6, GPIO 38 doesn't exist (only 0-30) — gate the init by target. */
+#if defined(CONFIG_IDF_TARGET_ESP32C6)
+    const int led_gpio = 8;
+#else
+    const int led_gpio = 38;
+#endif
     led_strip_handle_t led_strip;
     led_strip_config_t strip_config = {
-        .strip_gpio_num = 38,
+        .strip_gpio_num = led_gpio,
         .max_leds = 1,
         .led_model = LED_MODEL_WS2812,
         .color_component_format = LED_STRIP_COLOR_COMPONENT_FMT_GRB,
@@ -167,6 +197,27 @@ void app_main(void)
         led_strip_clear(led_strip);
     }
 
+    /* ADR-110 P4: 802.15.4 mesh time-sync (C6 only).
+     * Initialized BEFORE WiFi so it's available even when WiFi STA can't
+     * connect — the radios are physically independent on the C6.
+     * No-op on S3 (the helper compiles to an empty inline stub). */
+#if defined(CONFIG_IDF_TARGET_ESP32C6) && defined(CONFIG_C6_TIMESYNC_ENABLE)
+    esp_err_t ts_ret = c6_timesync_init(CONFIG_C6_TIMESYNC_CHANNEL);
+    if (ts_ret != ESP_OK) {
+        ESP_LOGW(TAG, "c6_timesync_init failed: %s (continuing without 15.4 sync)",
+                 esp_err_to_name(ts_ret));
+    }
+#endif
+
+    /* ADR-110 P5: Optionally arm LP-core wake-on-motion (C6 only, opt-in).
+     * Default off — only nodes flashed for battery-powered seed duty enable
+     * this in menuconfig. */
+#if defined(CONFIG_IDF_TARGET_ESP32C6) && defined(CONFIG_C6_LP_CORE_ENABLE)
+    if (c6_lp_core_was_motion_wake()) {
+        ESP_LOGI(TAG, "boot cause: LP-core motion wake (running CSI burst)");
+    }
+#endif
+
     /* Initialize WiFi STA (skip entirely under QEMU mock — no RF hardware) */
 #ifndef CONFIG_CSI_MOCK_SKIP_WIFI_CONNECT
     wifi_init_sta();
@@ -208,6 +259,26 @@ void app_main(void)
     }
 #endif
 
+    /* ADR-110 P3: Request TWT from the AP for deterministic CSI cadence.
+     * No-op on S3 (the helper compiles to an empty inline stub). On C6
+     * the AP may NACK — the helper logs and falls back to opportunistic.
+     * Called only after WiFi STA connect (wifi_init_sta blocks until then). */
+#if defined(CONFIG_IDF_TARGET_ESP32C6) && defined(CONFIG_C6_TWT_ENABLE)
+    c6_twt_setup_default();
+#endif
+
+    /* ADR-110 D1 workaround: ESP-NOW cross-node sync. Initialized after
+     * WiFi STA connects (ESP-NOW needs the WiFi driver up). Works on
+     * both S3 and C6 — replaces the broken 802.15.4 RX path in c6_timesync.
+     * Skip on QEMU mock (no real WiFi → no ESP-NOW). */
+#ifndef CONFIG_CSI_MOCK_SKIP_WIFI_CONNECT
+    esp_err_t espnow_ret = c6_sync_espnow_init();
+    if (espnow_ret != ESP_OK) {
+        ESP_LOGW(TAG, "c6_sync_espnow_init failed: %s (continuing without ESP-NOW sync)",
+                 esp_err_to_name(espnow_ret));
+    }
+#endif
+
     /* ADR-039: Initialize edge processing pipeline. */
     edge_config_t edge_cfg = {
         .tier              = g_nvs_config.edge_tier,