Bridging Sensors to Mobile Phones. Stephen Okay February 22nd 2012 The Abdus Salam Int l Center for Theoretical Physics Trieste, Italy

Transcription

1 Bridging Sensors to Mobile Phones Stephen Okay February 22nd 2012 The Abdus Salam Int l Center for Theoretical Physics Trieste, Italy

2 Mobile Phones can be sensor platforms too! Many mobile phones have built in accelerometers, light sensors, cameras, GPS receivers, and other sensors. These are definitely very useful in certain situations. But you still can t hook a water quality or temperature or other type of sensor to them without some difficulty...

3 ...or can you? New types of peripheral devices allow researchers to attach different sensors to your phone. There are basically two main approaches: Frequency modulation via headphone jack. USB Host adapter/bridge boards

4 Audio frequency modulation via headphone jack Modulated audio signals are converted to digital data and vice-versa. This is essentially a classic modem Pros: Well-understood, low-tech approach Does not require access agreeements, NDAs or other legal arrangements to use. Just plug-and-play with the hardware(software, of course, still needed on the phone) Cons Low-speed (approx baud) Dependent on quality/fidelity of headphone audio components. Vendor/manufacturer may use some frequencies internally further limiting useful frequency range(and thereby bandwidth)

5 Examples University of Michigan Hi-Jack project

6 Examples Credit-card swipe-reader

7 USB Adapters Many mobile phones have a USB port on them for data transfer to a PC, recharging, etc. Unlike RS-232 or TTL-serial devices, USB devices can t be connected to each other ad-hoc. USB Devices are either a USB-Host or USB-Client device

8 The real problem... The USB standard is both a data communications AND a power standard. A USB Host must provide 500mA power at 5V minimum to connected client devices in addition to protocol support. (Phones or cameras typically can t do that) USB Clients will communicate only with devices they recognize as a Host, like a desktop or laptop computer. Sensor carrier boards are USB Client devices, so how do we get them to talk to a phone, which is also a USB Client?

9 Answer... USB bridge/adapter boards which provide the necessary power as well as protocol support but processor-wise are just microcontrollers. Sparkfun IOIO Board Google Android Accessory Board...and about 12 others from different vendors

10 USB Bridge Boards(cont d) Features Analog & Digital I/O pins for attaching sensors, servos,motors, LEDs, etc. Open Hardware design, often with Open Source firmware. Currently Limited to Android devices (Apple requires a licensing agreement for attaching devices to their hardware)

11 The ThermalPod Project Huawei IDEOS Android Phone TMP-36 temperature sensor IOIO Bridge Board =

12 What s going on here? -USB Host on IOIO provides power and data exchange between phone and board -Android app on phone sends commands to IOIO via the Android Debug service. -Microcontroller on IOIO reads analog signal from temperature sensor & sends that back over the Android Debug Port

13 On the phone side... An Android application, written using the standard Android SDK and the IOIO Library, gets the sensor voltage data off the board and converts that to a temperature value that is then displayed on the screen. The IOIO Library works with any Android phone running Android 1.5 or later. The official ADK Library requires an Android or later. Different boards have different OS requirements.

14 Going further... Any of the analog or digital sensors used in the wireless sensor exercises in this School can be connected to one of these boards: Temperature Moisture Humidity Light etc. You can also set the pins to output and turn on LEDs, a buzzer/bell, turn a servo-motor, etc. Attach a Zigbee Coordinator node to the UART pins and use the phone as a sensor gateway.

15 Some useful links University of Michigan Hi-Jack Project: Details on USB Host/Client, etc.: Android Accessory Development Kit: IOIO Board - Freeduino USB Host: Generally useful USB Host Board blog: