Keep external I2C bus alive and add bus access functions

addon.c

@@ -409,23 +409,71 @@ esp_err_t addon_initialize(void) {
     if (external_i2c_bus_semaphore != NULL) {
         xSemaphoreGive(external_i2c_bus_semaphore);
         res = i2c_new_master_bus(&sao_i2c_master_config, &external_i2c_bus_handle);
+        ESP_LOGI(TAG, "External I2C bus init: %s (handle=%p)", esp_err_to_name(res), external_i2c_bus_handle);
         if (res == ESP_OK) {
             res = addon_detect(external_i2c_bus_handle, external_i2c_bus_semaphore, &external_eeprom_handle,
                                ADDON_LOCATION_EXTERNAL, &external_addon_descriptor);
             if (res == ESP_OK) {
                 ESP_LOGI(TAG, "External add-on detected");
                 addon_print_descriptor(external_addon_descriptor);
             } else {
-                ESP_LOGI(TAG, "No external add-on detected");
-                i2c_del_master_bus(external_i2c_bus_handle);
-                external_i2c_bus_handle = NULL;
-                vSemaphoreDelete(external_i2c_bus_semaphore);
-                external_i2c_bus_semaphore = NULL;
+                ESP_LOGI(TAG, "No external add-on detected (bus kept for plugin I2C access)");
             }
         }
     }
 #endif
 
+    // Debug: scan both I2C buses
+    ESP_LOGI(TAG, "Scanning internal I2C bus for devices...");
+    if (internal_i2c_bus_handle != NULL && internal_i2c_bus_semaphore != NULL) {
+        for (uint16_t addr = 0x08; addr < 0x78; addr++) {
+            if (xSemaphoreTake(internal_i2c_bus_semaphore, portMAX_DELAY) == pdTRUE) {
+                esp_err_t probe_res = i2c_master_probe(internal_i2c_bus_handle, addr, 100);
+                xSemaphoreGive(internal_i2c_bus_semaphore);
+                if (probe_res == ESP_OK) {
+                    ESP_LOGI(TAG, "  Internal bus: device at 0x%02X", addr);
+                }
+            }
+        }
+    } else {
+        ESP_LOGW(TAG, "  Internal bus not available");
+    }
+
+    ESP_LOGI(TAG, "Scanning external I2C bus for devices...");
+    if (external_i2c_bus_handle != NULL && external_i2c_bus_semaphore != NULL) {
+        for (uint16_t addr = 0x08; addr < 0x78; addr++) {
+            if (xSemaphoreTake(external_i2c_bus_semaphore, portMAX_DELAY) == pdTRUE) {
+                esp_err_t probe_res = i2c_master_probe(external_i2c_bus_handle, addr, 100);
+                xSemaphoreGive(external_i2c_bus_semaphore);
+                if (probe_res == ESP_OK) {
+                    ESP_LOGI(TAG, "  External bus: device at 0x%02X", addr);
+                }
+            }
+        }
+    } else {
+        ESP_LOGW(TAG, "  External bus not available (handle=%p, sem=%p)",
+                 external_i2c_bus_handle, external_i2c_bus_semaphore);
+    }
+
+    return ESP_OK;
+}
+
+esp_err_t addon_i2c_external_bus_get_handle(i2c_master_bus_handle_t* handle) {
+    if (handle == NULL) return ESP_ERR_INVALID_ARG;
+    if (external_i2c_bus_handle == NULL) return ESP_ERR_INVALID_STATE;
+    *handle = external_i2c_bus_handle;
+    return ESP_OK;
+}
+
+esp_err_t addon_i2c_external_bus_claim(void) {
+    if (external_i2c_bus_semaphore == NULL) return ESP_ERR_INVALID_STATE;
+    if (xSemaphoreTake(external_i2c_bus_semaphore, portMAX_DELAY) != pdTRUE) return ESP_FAIL;
+    return ESP_OK;
+}
+
+esp_err_t addon_i2c_external_bus_release(void) {
+    if (external_i2c_bus_semaphore == NULL) return ESP_ERR_INVALID_STATE;
+    xSemaphoreGive(external_i2c_bus_semaphore);
     return ESP_OK;
 }
 

include/addon.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <stdint.h>
+#include "driver/i2c_master.h"
 #include "esp_err.h"
 
 // Add-on descriptor
@@ -91,3 +92,8 @@ typedef struct _SAO {
 
 esp_err_t addon_initialize(void);
 esp_err_t addon_get_descriptor(addon_location_t location, addon_descriptor_t** out_descriptor);
+
+// External I2C bus access (QWIIC / SAO connector)
+esp_err_t addon_i2c_external_bus_get_handle(i2c_master_bus_handle_t* handle);
+esp_err_t addon_i2c_external_bus_claim(void);
+esp_err_t addon_i2c_external_bus_release(void);