DIY KICKR Headwind (Smart Fan)

This post will show you how to control your bicycle fan speed with your heart rate monitor.

DIY KICKR Headwind Parts List

Schematic

DIY KICKR Headwind Code

https://github.com/agrabbs/hrm_fan_control

/**
 * A modified BLE client that will read BLE HRM 
 * and control a relay
 * author Andrew Grabbs
 */

#include "BLEDevice.h"
//#include "BLEScan.h"

// Set to true to define Relay as Normally Open (NO)
#define RELAY_NO true

// Set number of relays
#define NUM_RELAYS 3

// Heart Rate Zones
#define ZONE_1 100 // 70 bpm
#define ZONE_2 120 // 100 bpm

// Assign each GPIO to a relay
uint8_t relayGPIOs[NUM_RELAYS] = {25, 26, 27};

// The remote service we wish to connect to.
static BLEUUID serviceUUID("0000180d-0000-1000-8000-00805f9b34fb");
// The characteristic of the remote service we are interested in.
static BLEUUID charUUID(BLEUUID((uint16_t)0x2A37));
//0x2A37

static boolean doConnect = false;
static boolean connected = false;
static boolean notification = false;
static boolean doScan = false;
static BLERemoteCharacteristic* pRemoteCharacteristic;
static BLEAdvertisedDevice* myDevice;

static void notifyCallback(
  BLERemoteCharacteristic* pBLERemoteCharacteristic,
  uint8_t* pData,
  size_t length,
  bool isNotify) {
    Serial.print("Heart Rate: ");
    Serial.print(pData[1], DEC);
    Serial.println("bpm");
    if(pData[1] == 0) {
      for(int i=1; i<=NUM_RELAYS; i++){
        digitalWrite(relayGPIOs[i-1], HIGH);
      }
    }
    else if(pData[1] <= ZONE_1 &amp;&amp; pData[1] > 0) {
      Serial.println("ZONE 1!");
      for(int i=1; i<=NUM_RELAYS; i++){
        digitalWrite(relayGPIOs[i-1], HIGH);
      }
      digitalWrite(relayGPIOs[0], LOW);
    }
    else if(pData[1] > ZONE_1 &amp;&amp; pData[1] <= ZONE_2) {
      Serial.println("ZONE 2!");
      for(int i=1; i<=NUM_RELAYS; i++){
        digitalWrite(relayGPIOs[i-1], HIGH);
      }
      digitalWrite(relayGPIOs[1], LOW);
    }
    else if(pData[1] > ZONE_2) {
      Serial.println("ZONE 3!");
      for(int i=1; i<=NUM_RELAYS; i++){
        digitalWrite(relayGPIOs[i-1], HIGH);
      }
      digitalWrite(relayGPIOs[2], LOW);
    }
}

class MyClientCallback : public BLEClientCallbacks {
  void onConnect(BLEClient* pclient) {
  }

  void onDisconnect(BLEClient* pclient) {
    connected = false;
    Serial.println("onDisconnect");
  }
};

bool connectToServer() {
    Serial.print("Forming a connection to ");
    Serial.println(myDevice->getAddress().toString().c_str());
    
    BLEClient*  pClient  = BLEDevice::createClient();
    Serial.println(" - Created client");

    pClient->setClientCallbacks(new MyClientCallback());

    // Connect to the remove BLE Server.
    pClient->connect(myDevice);  // if you pass BLEAdvertisedDevice instead of address, it will be recognized type of peer device address (public or private)
    Serial.println(" - Connected to server");

    // Obtain a reference to the service we are after in the remote BLE server.
    BLERemoteService* pRemoteService = pClient->getService(serviceUUID);
    if (pRemoteService == nullptr) {
      Serial.print("Failed to find our service UUID: ");
      Serial.println(serviceUUID.toString().c_str());
      pClient->disconnect();
      return false;
    }
    Serial.println(" - Found our service");


    // Obtain a reference to the characteristic in the service of the remote BLE server.
    pRemoteCharacteristic = pRemoteService->getCharacteristic(charUUID);
    if (pRemoteCharacteristic == nullptr) {
      Serial.print("Failed to find our characteristic UUID: ");
      Serial.println(charUUID.toString().c_str());
      pClient->disconnect();
      return false;
    }
    Serial.println(" - Found our characteristic");

    // Read the value of the characteristic.
    if(pRemoteCharacteristic->canRead()) {
      std::string value = pRemoteCharacteristic->readValue();
      Serial.print("The characteristic value was: ");
      Serial.println(value.c_str());
    }

    if(pRemoteCharacteristic->canNotify())
      pRemoteCharacteristic->registerForNotify(notifyCallback);

    connected = true;
    return true;
}
/**
 * Scan for BLE servers and find the first one that advertises the service we are looking for.
 */
class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {
 /**
   * Called for each advertising BLE server.
   */
  void onResult(BLEAdvertisedDevice advertisedDevice) {
    Serial.print("BLE Advertised Device found: ");
    Serial.println(advertisedDevice.toString().c_str());

    // We have found a device, let us now see if it contains the service we are looking for.
    if (advertisedDevice.haveServiceUUID() &amp;&amp; advertisedDevice.isAdvertisingService(serviceUUID)) {

      BLEDevice::getScan()->stop();
      myDevice = new BLEAdvertisedDevice(advertisedDevice);
      doConnect = true;
      doScan = true;

    } // Found our server
  } // onResult
}; // MyAdvertisedDeviceCallbacks


void setup() {
  Serial.begin(115200);
  Serial.println("Starting Arduino BLE Client application...");
  BLEDevice::init("");
  // Set all relays to off when the program starts - if set to Normally Open (NO), the relay is off when you set the relay to HIGH
  for(int i=1; i<=NUM_RELAYS; i++){
    pinMode(relayGPIOs[i-1], OUTPUT);
    if(RELAY_NO){
      digitalWrite(relayGPIOs[i-1], HIGH);
    }
    else{
      digitalWrite(relayGPIOs[i-1], LOW);
    }
  }

  // Retrieve a Scanner and set the callback we want to use to be informed when we
  // have detected a new device.  Specify that we want active scanning and start the
  // scan to run for 5 seconds.
  BLEScan* pBLEScan = BLEDevice::getScan();
  pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
  pBLEScan->setInterval(1349);
  pBLEScan->setWindow(449);
  pBLEScan->setActiveScan(true);
  pBLEScan->start(5, false);
} // End of setup.


// This is the Arduino main loop function.
void loop() {
  // If the flag "doConnect" is true then we have scanned for and found the desired
  // BLE Server with which we wish to connect.  Now we connect to it.  Once we are 
  // connected we set the connected flag to be true.
  if (doConnect == true) {
    if (connectToServer()) {
      Serial.println("We are now connected to the BLE Server.");
    } else {
      Serial.println("We have failed to connect to the server; there is nothin more we will do.");
    }
    doConnect = false;
  }

  // If we are connected to a peer BLE Server, update the characteristic each time we are reached
  // with the current time since boot.
  if (connected) {
    if (notification == false) {
        Serial.println("Turning Notification On");
        const uint8_t onPacket[] = {0x01, 0x0};
        pRemoteCharacteristic->getDescriptor(BLEUUID((uint16_t)0x2902))->writeValue((uint8_t*)onPacket, 2, true);
        notification = true;
    }
  }else if(doScan){
    BLEDevice::getScan()->start(0);  // this is just eample to start scan after disconnect, most likely there is better way to do it in arduino
  }
  
  delay(1000); // Delay a second between loops.
} // End of loop

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