Hi,kolban. Thanks for your reply! Your are right. When we call esp_ble_gattc_read_char() in such situations that is when the BLE connection is broken, I got the ESP_GATT_ERROR from the "status" field under ESP_GATTC_READ_CHAR_EVT event. I haven't process this error, that caused ESP32 failed since I still tried to do something with the BLE things. Thanks again! I also very appreciate your excellent workings on ESP. I have read your book long before, it's very informative. Sometimes I wonder how can you be such productive and always being enthusiastic. Any personal experiences shared on embedded system would be nice