esphome, esp32 ble tracker and Home Assistant mqtt_room sensors

esphome_ble_config.yaml

# MQTT broker configuration
mqtt:
  broker: !secret mqtt_broker
  username: !secret mqtt_username
  password: !secret mqtt_password
  discovery: False # Only if you use the HA API usually
  id: mqtt_client

# Define the room for this ESP32 node
substitutions:
  room_name: bedroom
  maximum_distance: 5

# Push the room name into a global
globals:
  - id: room_topic
    type: std::string
    initial_value: '"room_presence/${room_name}"'
  - id: max_distance
    type: std::float
    initial_value: '${maximum_distance}'

# Configure the esp32_ble_tracker to push beacon advertisements to MQTT
  on_ble_advertise:
    - then:
        - lambda: |-
            if (x.get_ibeacon().has_value()) {
                std::string uuid;
                esp_bt_uuid_t raw_uuid = x.get_ibeacon().value().get_uuid().get_uuid();

                char sbuf[64];
                char *bpos = sbuf;

                switch (raw_uuid.len) {
                    case ESP_UUID_LEN_128:
                        for (int8_t i = 0; i <= 15; i++) {
                            sprintf(bpos, "%02x", raw_uuid.uuid.uuid128[i]);
                            bpos += 2;

                            if (i == 6 || i == 8 || i == 10 || i == 12)
                                  sprintf(bpos++, "-");
                        }

                        sbuf[47] = '\0';
                        uuid.assign(sbuf);
                        break;
                    default:
                        uuid = x.get_ibeacon().value().get_uuid().to_string();
                        std::transform(uuid.begin(), uuid.end(), uuid.begin(), [](unsigned char c){ return std::tolower(c); });
                        break;
                }

                char mbuf[32] = {0};
                sprintf(mbuf, "-%hu-%hu", x.get_ibeacon().value().get_major(), x.get_ibeacon().value().get_minor());
                uuid.append(mbuf);

                int8_t tx_power = -69;
                float dist = pow(10, (float)(tx_power - x.get_rssi()) / (10 * 2));
                
                if(dist < max_distance) {
                  ESP_LOGD("ble_adv", "Sending MQTT room update for '%s' (%s): %.03fm (%d rssi)", 
                  x.get_name().c_str(), uuid.c_str(), dist, x.get_rssi());

                  id(mqtt_client).publish_json(id(room_topic), [=](JsonObject root) {
                      root["id"] = uuid;
                      root["name"] = x.get_name();
                      root["distance"] = dist;
                  });
                }
            }

ha_configuration.yaml

# Configure the sensors in Home Assistant as normal:
sensor:
  - platform: mqtt_room
    name: Test beacon 1
    device_id: aabbccdd-eeff-1122-3344-5566778899aa-0001-0002
    state_topic: room_presence