Getting the bluetooth RSSI

[MarusGradinaru]

Hi,
It is possible to read the RSSI of the bluetooth connection if I configured my ESP32 device as a A2DP audio sink ?
I use Arduino framework in Platform IO.

[pschatzmann]

Sure, just search in the class documentation for all methods containing rssi!

[MarusGradinaru]

Is that how it needs to be done ?

#include <Arduino.h>
#include "AudioTools.h"
#include "BluetoothA2DPSink.h"

I2SStream i2s;  
BluetoothA2DPSink a2dp_sink(i2s);

void rssi_callback(esp_bt_gap_cb_param_t::read_rssi_delta_param &rssi) {
  Serial.print("RSSI: ");
  Serial.print(rssi.rssi_delta);
  Serial.println(" dBm");
}

void read_data_stream(const uint8_t* data, uint32_t length) {
  static size_t total_bytes = 0;
  static unsigned long lastPrint = 0;
  total_bytes += length;
  unsigned long now = millis();
  if (now - lastPrint >= 1000) {
    Serial.printf("Received audio data: %u bytes\n", total_bytes);
    total_bytes = 0;
    lastPrint = now;
  }
}

void setup() {
  Serial.begin(115200);
  delay(1000);

  Serial.println("Initializing Bluetooth A2DP...");
  a2dp_sink.set_stream_reader(read_data_stream, false); // because I don't have a DAC connected yet
  a2dp_sink.start("ESP32 Speakers");  
  a2dp_sink.set_rssi_active(true);
  a2dp_sink.set_rssi_callback(rssi_callback);  
  Serial.println("Bluetooth ready ! Waiting for connections...");
}

unsigned long last_rssi_check = 0;

void loop() {
  if (a2dp_sink.is_connected() && (millis() - last_rssi_check) > 3000) {
    a2dp_sink.update_rssi();          
    last_rssi_check = millis();
  }
  delay(100);
}

The code it seems to be working, because it show a RSSI value, but I'm not sure... It has a verry big lag, especially when the music is stopped. The value is updated at about a few minutes. It shows -33dBm at 10 meters and -19dBm at 0 meters. Then I play music and the lag is shorter ( a few seconds ). But with the phone beside the ESP32 I get 0dBm. At 17 meters: -25dBm and at 34 meters -35 dBm in free air. Is this normal ?

[MarusGradinaru]

Sure, just search in the class documentation for all methods containing rssi!

I found how rssi is requested in your library example folder, and I understud how it works.
But my only concern is if the RSSI I received is real, i.e. -25 dBm at 17m and -35 dBm at 34m... From what I've read on the net, it's unusually good. At 34m they say I should have around -60 dBm...
I tested with a Xiaomi Redmi Note 10 Pro with BT 5.1 and ESP32-DevKitC with WROVER-E with BT 4.2

[pschatzmann]

I never used this myself: so I don't know what to expect: here is the link to the official IDF documentation that indicates that you can expect a value in the range fo -128 ~127,

The Golden Receive Power Range is:
#define ESP_BT_GAP_RSSI_HIGH_THRLD -20 /*!< High RSSI threshold /
#define ESP_BT_GAP_RSSI_LOW_THRLD -45 /!< Low RSSI threshold */

I think this matches with what you describe above...