Distance tracking for BLE iBeacons in esphome
This code utilizes esphome's esp32_ble_tracker component to track nearby iBeacons. The distance is estimated using the received RSSI and the beacon's advertised 1 meter reference RSSI. The distance is then passed through an adaptive low pass filter before being reported. This works on my personal boards and setup, YMMV.
See the example configuration.yaml. Add new BeaconTracker objects in a lambda under the esphome: on_boot: section of your configuration.yaml, with an iBeacon UUID and unique name for each device you want to track. Add a lambda calling the parseAdvertisement function in esp32_ble_tracker: on_ble_advertise:. For each tracker, set up a template sensor that gets a tracker using getTracker() and then calls get_dist() on the returned object. The 1€ filter fcmin and beta parameters are optionally adjustable when creating a tracker. If a sensor is too jittery when stationary, decrease fcmin. If the lag when moving is unacceptable, increase beta. Other parameters are adjustable by changing the #defines in the header file. The path loss constant can be adjusted if the distance doesn't scale right as you move the tracker away from the ESP32. The timeout and buffer size will affect the jitter and lag as well.
The UUID decoding in ESPhome is currently bugged, details here. Old versions of this header required that you either reverse the bytes in the UUID you use to add the tracker, or implement the fix I posted in that thread. The header has now been updated to take care of this for you.
When an iBeacon advertisement is received, the distance is calculated based on the received RSSI and the advertised reference power. The calculated distance is stored in a buffer. The buffer is kept to a maximum size defined by BUF_SIZE. Samples older than TIMEOUT seconds are also removed. The 33rd percentile sample of the remaining buffer is then fed into a 1€ filter (adapted from the C++ example by Jonathan Aceitune here and fixed according to this issue). By default, the reported value if there are no samples remaining in the buffer is NAN, which causes the Home Assistant sensor to go unavailable.