Unable to get HRM data from mi band.

[akashsaggu96]

i am using Mi band 3, after short interval it keep on disconnecting
i am unable to retrieve the heart rate from the band, it is notifying
<CBService: 0x1c467b340, isPrimary = YES, UUID = Heart Rate>
<CBCharacteristic: 0x1c42a2400, UUID = 2A37, properties = 0x10, value = (null), notifying = NO>

following method is not calling

func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {

    if characteristic.uuid == BLE_Heart_Rate_Measurement_Characteristic_CBUUID {
        
        // STEP 13: we generally have to decode BLE
        // data into human readable format
        let heartRate = deriveBeatsPerMinute(using: characteristic)
        
        DispatchQueue.main.async { () -> Void in
            
            UIView.animate(withDuration: 1.0, animations: {
                self.beatsPerMinuteLabel.alpha = 1.0
                self.beatsPerMinuteLabel.text = String(heartRate)
            }, completion: { (true) in
                self.beatsPerMinuteLabel.alpha = 0.0
            })
            
        } // END DispatchQueue.main.async...

    } // END if characteristic.uuid ==...
    
    if characteristic.uuid == BLE_Body_Sensor_Location_Characteristic_CBUUID {
        
        // STEP 14: we generally have to decode BLE
        // data into human readable format
        let sensorLocation = readSensorLocation(using: characteristic)

        DispatchQueue.main.async { () -> Void in
            self.sensorLocationTextField.text = sensorLocation
        }
    } // END if characteristic.uuid ==...
    
} // END func peripheral(... didUpdateValueFor charact