By Behlol Nawaz
In a previous post, we started looking into some of the semester projects from the 5th semester electrical engineering students (Fall ‘14), for their subject “Electronic Circuit Design”. The requirement was that the students had to design and construct a device that utilized a Bluetooth Low Energy (BLE) chip and an Android phone application.
In the first post, we saw “Audink”, a device that could convert any normal speakers into wireless ones that could stream audio perfectly from an Android phone.
In this entry we are going to look at a watch-like wearable device, that can receive notifications from an Android phone, display them to the wearer and receive feedback from the user in the form of gestures.
Students: Saad Amin, Zuqair Younis and Faizan Tariq.
(BEE-4 SEECS, NUST)
According to the students who worked on this project, they decided to “try their luck” on a wearable device after seeing the increasing worldwide interest in wearable technology. Their motivation was to try out the design and assembly of a wearable device, see what sort of challenges such a project entails and if a future adventure into the land of wearable technology might be feasible for them.
The basic function of the device is that it receives notifications regarding calls and text messages from the paired Android phone through an application developed for this purpose. The device then communicates orders back to the phone, based on the gestures of the user’s hand.
In accordance with the requirements, their project has two main parts, the Android application and the Bluetooth chip based hardware.
The hardware part itself has three main components. The Bluetooth chip’s board (RFduino, as recommended), a motion sensor and an O-LED display.
The motion sensor is an Inertial Measurement Unit (IMU), a device that can give its velocity, orientation and the forces experienced through different combinations of accelerometers, gyroscopes and magnetometers. The specific device used here is the MPU-6050 by InvenSense.
The small OLED (organic light emitting diode) screen displays the notifications.
The RFduino board houses the Bluetooth chip and the microcontroller. So it has the overall control of the Bluetooth communication, the IMU and OLED display. Both the IMU and the OLED screen are interfaced via the I2C protocol.
(“I2C” or “inter-integrated circuit” protocol is the protocol used for communication across the I2C bus. It requires only two signal wires for the communication of information. It is one of the more widely used serial communication protocols for communication between micro-controllers and peripherals.)
When there is an incoming call or a text message is received, the application on the phone communicates it to the hardware via Bluetooth. The RFduino is programmed to interpret this and display a notification to the user on the O-LED display. The user can then respond to the notification with a specific gesture.
Notify-U can recognize three gestures. Rotation of the wrist for cancelling the incoming call, rise of the forearm for sending a text message (that had been pre-set by the user) and dropping of the forearm for clearing the O-LED screen.
The gesture recognition algorithm runs on RFduino’s microcontroller, using the IMU’s output. It communicates orders to the phone via Bluetooth, after recognizing the user’s gestures.
Given the nature of the project, it wouldn’t come as a surprise that the students faced a number of challenges along the way. It was the first time that the group had worked on an IMU and a display of this type. Because of the lack of documentation for the MPU-6050, they had to start off with an already existing code for the initialization of the device and then build their algorithms on top of it.
Interfacing multiple devices with the RFduino via the I2C protocol had its own challenges. One unexpected problem they encountered was that their device would crash inexplicably during operation. They soon found out that the cause was the disconnection of I2C lines during operation. It was partially resolved when they moved to a permanent circuit on a printed circuit board (PCB).
The students were very satisfied with the final shape of Notify-U and the fluidity of its operation. It scored high marks from the instructor as well.
This project has a plenty of room for extension. The first thing that probably comes to mind is receiving notifications from different social networks in addition to calls and text messages. The students say they are looking ahead to see if the project is worth extending to a Final Year Project (FYP).