diff --git a/components/hal_i2s/hal_i2s.c b/components/hal_i2s/hal_i2s.c
index 67abc31..ea26949 100644
--- a/components/hal_i2s/hal_i2s.c
+++ b/components/hal_i2s/hal_i2s.c
@@ -9,6 +9,9 @@
 #include "driver/gpio.h"
 #include "driver/i2s_std.h"
 #include "esp_log.h"
+#include "esp_heap_caps.h"
+#include "freertos/FreeRTOS.h"
+#include <stdlib.h>
 
 #define TAG "hal_i2s"
 
@@ -18,6 +21,10 @@
 static i2s_chan_handle_t s_spk_handle = NULL;
 static i2s_chan_handle_t s_mic_handle = NULL;
 
+#define HAL_I2S_CAP_FRAME_SAMPLES 320
+#define HAL_I2S_CAP_IN_BYTES (HAL_I2S_CAP_FRAME_SAMPLES * 2 * (int)sizeof(int16_t))
+static int16_t *s_rx_scratch = NULL;
+
 void hal_audio_pa_set(bool enable)
 {
     gpio_set_level(PLIP_PA_ENABLE, enable ? 1 : 0);
@@ -95,3 +102,44 @@ esp_err_t hal_i2s_init(void)
     }
     return ESP_OK;
 }
+
+esp_err_t hal_i2s_capture_begin(void)
+{
+    if (!s_mic_handle) {
+        ESP_LOGE(TAG, "capture_begin: pas de canal RX");
+        return ESP_ERR_INVALID_STATE;
+    }
+    if (s_rx_scratch) return ESP_OK;  /* idempotent */
+    s_rx_scratch = heap_caps_malloc(HAL_I2S_CAP_IN_BYTES, MALLOC_CAP_SPIRAM);
+    if (!s_rx_scratch) s_rx_scratch = malloc(HAL_I2S_CAP_IN_BYTES);
+    if (!s_rx_scratch) return ESP_ERR_NO_MEM;
+    ESP_LOGI(TAG, "capture_begin: pret (full-duplex, TX actif)");
+    return ESP_OK;
+}
+
+int hal_i2s_capture_read_frame(int16_t *mono_out, int n_samples, int64_t *rms_sq_out)
+{
+    if (!s_rx_scratch || !s_mic_handle) return -1;
+    size_t bytes_read = 0;
+    esp_err_t ret = i2s_channel_read(s_mic_handle, s_rx_scratch,
+                                     HAL_I2S_CAP_IN_BYTES, &bytes_read,
+                                     pdMS_TO_TICKS(100));
+    if (ret != ESP_OK || bytes_read == 0) return 0;  /* timeout */
+    int n = (int)(bytes_read / (2 * sizeof(int16_t)));
+    if (n > n_samples) n = n_samples;
+    int64_t rms_sq = 0;
+    for (int i = 0; i < n; i++) {
+        int32_t l = s_rx_scratch[i * 2];
+        int32_t r = s_rx_scratch[i * 2 + 1];
+        int16_t mono = (int16_t)((l + r) / 2);
+        mono_out[i] = mono;
+        rms_sq += (int64_t)mono * mono;
+    }
+    if (rms_sq_out) *rms_sq_out = (n > 0) ? rms_sq / n : 0;
+    return n;
+}
+
+void hal_i2s_capture_end(void)
+{
+    if (s_rx_scratch) { free(s_rx_scratch); s_rx_scratch = NULL; }
+}
diff --git a/components/hal_i2s/include/hal_i2s.h b/components/hal_i2s/include/hal_i2s.h
index 87a6554..69a6ba2 100644
--- a/components/hal_i2s/include/hal_i2s.h
+++ b/components/hal_i2s/include/hal_i2s.h
@@ -21,6 +21,12 @@ i2s_chan_handle_t hal_i2s_mic_handle(void);
 /* Enable/disable the speaker power amplifier (GPIO21, active HIGH). */
 void hal_audio_pa_set(bool enable);
 
+/* Microphone capture (RX). capture_begin allocates a scratch buffer; read_frame
+ * reads one 20 ms frame, downmixes L+R to mono, and reports mean energy. */
+esp_err_t hal_i2s_capture_begin(void);
+int hal_i2s_capture_read_frame(int16_t *mono_out, int n_samples, int64_t *rms_sq_out);
+void hal_i2s_capture_end(void);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/main/app_main.c b/main/app_main.c
index 9bfac41..abfd4de 100644
--- a/main/app_main.c
+++ b/main/app_main.c
@@ -17,14 +17,19 @@ void app_main(void)
      * avec la tache tone (i2s_channel_write qui tourne en parallele). */
     ESP_ERROR_CHECK(slic_init());
     audio_router_init();
-    audio_router_dialtone_start();
-    ESP_LOGI(TAG, "tonalite de numerotation demarree (combine decroche pour ecouter)");
-    /* Sonde temporaire de polarite hook (a retirer en Task 6). */
+    /* Sonde RMS micro (valide chemin LIN2/RIN2) — a retirer en Task 6. */
+    ESP_ERROR_CHECK(hal_i2s_capture_begin());
+    int16_t cap[320];
     for (int i = 0; i < 20; i++) {
-        ESP_LOGI(TAG, "HOOK sonde: offhook=%d (niveau brut SHK)", (int)slic_is_offhook());
+        int64_t rms_sq = 0;
+        int got = hal_i2s_capture_read_frame(cap, 320, &rms_sq);
+        ESP_LOGI(TAG, "MIC sonde: offhook=%d frame=%d rms_sq=%lld",
+                 (int)slic_is_offhook(), got, (long long)rms_sq);
         vTaskDelay(pdMS_TO_TICKS(500));
     }
-    ESP_LOGI(TAG, "boot OK — Phase 3 Task 1 SLIC KS0835");
+    audio_router_dialtone_start();
+    ESP_LOGI(TAG, "tonalite de numerotation demarree (combine decroche pour ecouter)");
+    ESP_LOGI(TAG, "boot OK — Phase 3 Task 2 capture micro hal_i2s");
     while (true) {
         ESP_LOGI(TAG, "heartbeat");
         vTaskDelay(pdMS_TO_TICKS(5000));