Week Twelve: Networking

This week I made a door lock that opens via Bluetooth with an app on my phone.


I used a solenoid design for a door strike I had lying around. The solenoid is designed for 12V but I found that it engaged just fine with a 9V battery. I removed the existing lock from my bedroom door and put in the solenoid and assembled a simple circuit with a microcontroller, MOSFET, and battery.


I was a backer of the RFduino kickstarter project and received my reward a couple weeks ago so I decided to use it for this project. The RFduino is a breakout board for an STM32 with a built-in bluetooth module. The STM32 is programmable with the Arduino IDE and has a very easy to use API for communicating via bluetooth. Here's the code I used to set up bluetooth and drive the gate on a MOSFET for one second when the text "open" is received to engage the solenoid.

void setup() {
  RFduinoBLE.advertisementData = "doorlock";

void RFduinoBLE_onReceive(char *data, int len)
  if (strcmp(data, "open") == 0) {
    digitalWrite(1, HIGH);
    digitalWrite(1, LOW);

iOS App

Next I wrote an iOS app to communicate over Bluetooth with the RFduino. I used the RFduino framework to discover and send data to the device. First, I started a scan for an RFduino:

[[RFduinoManager sharedRFduinoManager] setDelegate:self];
[[RFduinoManager sharedRFduinoManager] startScan];

Next I implemented the callbacks for discover and connect to an RFduino.

- (void)didDiscoverRFduino:(RFduino *)rfduino
    if (!self.rfduino)
        [[RFduinoManager sharedRFduinoManager] connectRFduino:rfduino];

- (void)didConnectRFduino:(RFduino *)rfduino
    self.rfduino = rfduino;
    [[RFduinoManager sharedRFduinoManager] stopScan];

Finally, to send data I just call:

[self.rfduino send:[@"open" dataUsingEncoding:NSUTF8StringEncoding]];