What is the difference between scan Window, Interval and scanTime in the ESP32_BLE_Arduino Library? - c++

Question

I am looking at the basic BLE_Scan.ino sketch from the ESP32_BLE_Arduino library. I've modified it to do 5 scans in a row before anything else. I would like to do a few scans very quickly in order to average them. (See code below)
I cannot figure out the difference between scan interval, scan window and the scanTime paramter.
I understand that the window should be how long to scan, this should happen every interval. I am not sure waht the scanTime paramamter does.
I have adjusted the scan interval and scan window to low numbers. Have also put the scanTime variable as low as it can be (1, since it is an int, and it cannot be 0). None of these fixes seem to allow me to do quick scan. Still seems to have a second or two delay between printing "scan!!" each time.
Any help in clarifying what these 3 parameter do, or can point out what I am doing wrong is appreciated.
(Also, my first post on SO, so let me know if I can fix up how I have asked this question, and I will!)
Thanks!!
/*
Based on Neil Kolban example for IDF: https://github.com/nkolban/esp32-snippets/blob/master/cpp_utils/tests/BLE%20Tests/SampleScan.cpp
Ported to Arduino ESP32 by Evandro Copercini
*/
#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEScan.h>
#include <BLEAdvertisedDevice.h>
int scanTime = 1; //In seconds
BLEScan* pBLEScan;
class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {
void onResult(BLEAdvertisedDevice advertisedDevice) {
Serial.printf("Advertised Device: %s \n", advertisedDevice.toString().c_str());
}
};
void setup() {
Serial.begin(115200);
Serial.println("Scanning...");
BLEDevice::init("");
pBLEScan = BLEDevice::getScan(); //create new scan
pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
pBLEScan->setActiveScan(true); //active scan uses more power, but get results faster
pBLEScan->setInterval(50); //interval (how often there is a scan)
pBLEScan->setWindow(49); // window (how long the scans are) must be <= interval
Serial.begin(115200);
}
void loop() {
// put your main code here, to run repeatedly:
//bluetooth scan
for(int x = 0; x < 5; x ++){
BLEScanResults foundDevices = pBLEScan->start(1, true);
Serial.println("Scan!!");
}
delay(200);
}

Answer 1

The Scan_Window configuration parameter defines the amount of time for the duration of the scan. The Inquiry_Scan_Window can only be less than or equal to the Scan_Interval. [Time Default: 11.25 ms]
The Scan_Interval configuration parameter defines the amount of time between consecutive scans. This is defined as the time interval from when the BR/EDR Controller started its last scan until it begins the next scan. [Default: 2.5 sec]
Scan Timeout: A device may scan for a limited duration of time