There is a wide selection of mobile phones on the market. For our development, we chose Nokia 6210 Navigator due to its ability to run Java, accompanied by Bluetooth communication, and its small form factor. The phone mainly acts as a remote control for setting up the microcontroller. It provides the ability to adjust the trial condition configurations and let the microcontroller knows how the sensors and actuators are connected, eliminating the need for uploading a separate piece of code on microcontroller. It also acts as a visual feedback device for the user as well since it can display important gait parameters in real-time.
We selected an Arduino Mega as our development microcontroller due to its large numbers of analog input pins, digital I/O pins, UARTs, and its complete development form factor. This provides us with fast development time for our first testing device. For more information on microcontroller selection, please see Microcontroller Table
We also used a stackable prototyping shield board to prototype our customized C2 Tactor (vibration motor) driver circuit.
C2 Tactor is a special kind of vibration motors. It requires a 250 Hz sine wave drive circuit. Its magnitude of vibration corresponds to the amplitude of the sine wave. Since we cannot use a typical PWM signal on microcontroller to drive the tactors, we have implemented an adjustable voltage regulator with digital potentiometer to drive these tactors.
See circuit diagrams.
Flexi Force is used as simple foot switch. However, it has the potential to do an accurate force measurement with some calibrations.
Read more: Portable Haptics System Hardware