Hello again.
I have a simple program on an NRF52840. The program transmits sensor data to the nRF Connect App. It all seems to work, however, I’ve noticed that when I press “DISCONNECT” on the nRF Connect App, the NRF52840 seemingly stays connected. For this simple program, it’s not a big deal, however, I imagine this would start to cause issues when connecting to a PC or Chrome browser Application.
Here’s a simplified version of my code. All this is is the MAX30102 example code, transmitted via BLE.
// This script connects a Seeed Xiao NRF52840 to the
// NRF Connect App and displays Average Heart Rate
// from the MAX30102 Sensor.
// Data is sent as a String.
#include <ArduinoBLE.h>
#include <Wire.h>
#include “MAX30105.h”
#include “heartRate.h”
MAX30105 particleSensor;
const byte RATE_SIZE = 4; //Increase this for more averaging. 4 is good.
byte rates[RATE_SIZE]; //Array of heart rates
byte rateSpot = 0;
long lastBeat = 0; //Time at which the last beat occurred
float beatsPerMinute;
int beatAvg;
// Bluetooth® Low Energy HR Service
BLEService HRService(“19B10000-E8F2-537E-4F6C-D104768A1214”);
// Bluetooth® Low Energy Switch Characteristic - custom 128-bit UUID, read and writable by central
BLEStringCharacteristic switchCharacteristic(“19B10001-E8F2-537E-4F6C-D104768A1214”, BLERead | BLENotify, 20);
void setup() {
Serial.begin(9600);
Serial.println(“Initializing…”);
// Initialize sensor
if (!particleSensor.begin(Wire, I2C_SPEED_FAST)) //Use default I2C port, 400kHz speed
{
Serial.println("MAX30105 was not found. Please check wiring/power. "); while (1);}
Serial.println(“Place your index finger on the sensor with steady pressure.”);
particleSensor.setup(); //Configure sensor with default settings
particleSensor.setPulseAmplitudeRed(0x0A); //Turn Red LED to low to indicate sensor is running
particleSensor.setPulseAmplitudeGreen(0); //Turn off Green LED
// begin initialization
if (!BLE.begin()) {
Serial.println("starting the HR Demo has failed!"); while (1);}
// set advertised local name and service UUID:
BLE.setLocalName(“Nelevate HR 1”);
BLE.setAdvertisedService(HRService);
// add the characteristic to the service
HRService.addCharacteristic(switchCharacteristic);
// add service
BLE.addService(HRService);
// start advertising
BLE.advertise();
Serial.println(“Seeed Studio XIAO nRF52840 active, waiting for connections…”);
}
void loop() {
// listen for Bluetooth® Low Energy peripherals to connect:
BLEDevice central = BLE.central();
// if a central is connected to peripheral:
if (central) {
Serial.print("Connected to central: "); // print the central's MAC address: Serial.println(central.address()); // while the central is still connected to peripheral: while (central.connected()){ long irValue = particleSensor.getIR(); if (checkForBeat(irValue) == true) { //We sensed a beat! long delta = millis() - lastBeat; lastBeat = millis(); beatsPerMinute = 60 / (delta / 1000.0); if (beatsPerMinute < 255 && beatsPerMinute > 20) { rates\[rateSpot++\] = (byte)beatsPerMinute; //Store this reading in the array rateSpot %= RATE_SIZE; //Wrap variable //Take average of readings beatAvg = 0; for (byte x = 0 ; x < RATE_SIZE ; x++) beatAvg += rates\[x\]; beatAvg /= RATE_SIZE; } } if (irValue < 50000){ Serial.println("No Finger Detected"); String myString = "No Finger"; switchCharacteristic.setValue(myString); } else{ Serial.print("Avg BPM: "); Serial.println(beatAvg); String myString = "Avg BPM: "; myString += String(beatAvg); switchCharacteristic.setValue(myString); } } // when the central disconnects, print it out: Serial.print(F("Disconnected from central: ")); Serial.println(central.address());}
}
NOTE: When I hit “DISCONNECT” on the nRF Connect App, the last print message does not appear in the Serial Console.
When my friend tested this code by connecting directly to a simple Chrome Application that he wrote, it will connect and work fine; but as soon as he tries to connect from a different computer, the NRF52840 refuses to connect. All signs point to the NRF52840 not disconnecting from the initial Chrome Application.
I tried to add the following code after the Disconnect Serial Print at the bottom of the program, but it did not resolve anything:
BLE.disconnect();
BLE.advertise();
Any ideas??
Best,
Joe
This Git.
PJ 