MotivationDevices of Future
Could we build a device that enables better communication in rural India for under Rs. 500? In this section we are going to discuss about such a device which will help us in acheiving this objective. Only design information is given.
Peer-to-Peer Pager
This minimal thing is something like a pocket MP3 player crossed with a pager. It contains a power source, a CPU, energy storage such as a battery, some volatile memory, some nonvolatile memory, a short-range radio, audio codec hardware, and audio input and output to which you can attach headphones and a small microphone, and interact with the device entirely by audio. Perhaps this device could be as small as an adult's finger so it can be carried all the time, like jewellery.
Applications
- send email to other users of similar devices, as voice. Essentially this device lets you talk to friends and family even when they're not nearby.
- send it over the Internet as well, perhaps using Bluetooth to a cellphone.
- keep notes to yourself prices, to-do items, etc.
- compose and publish vocal essays, prayers, songs, etc.
- listen to the essays, etc. of others
- be notified of events happening out of your sight but within multihop radio range
- use voice synthesis software to read existing text, such as email or ebooks
Design Components
- CPU
There are many CPUs that can operate under 25 milliwatts at a few MIPS.
Atmel's AVR-based FPSLIC
FPGAless CPUs like the ATtiny11 - Power Sources
Disposable batteries, mechanical generators, grid power, solar cells, and car-battery power. - Energy Storage
- Volatile memory
DRAM is far too power-hungry for such a device, so static CMOS RAM may be the only usable alternative. A few megabytes would be nice in order to support a wide range of applications, but only a few kilobytes are needed for the basic networking and voice-mail logic. However, if the CPU is running audio codecs, it will probably need at least a few hundred kilobytes to support that.
- Nonvolatile Memory
There are only two presently feasible alternatives for nonvolatile memory in such a cheap and low-power device: "flash" EEPROM, and nothing. The "volatile" memory might be sufficiently nonvolatile under some circumstances; if it can survive for weeks or months on the residual energy stored in the energy storage device when the device has too little power to run the CPU, particularly if recharging is quick and easy (as with the mechanical generator and solar types), the advantage of "flash" may be small.
- Audio Input and Output
The quantities of energy required to be stored for such a device might occupy a wide range; solar pagers might need to store only enough energy for night operation, which might be quite minimal, while pagers powered off the grid might need to store enough energy for a week's operation, and at the extreme end, a device the user can re-power by shaking (like the Forever Flashlight) might only need a few minutes of power consumption.
So an energy storage system might usefully store anything from 1 mAh (if the user can easily add more energy) to 20 mAh (for a system solar) to 110mAh (for a weekly-grid-charged system).
Methods are implemented to get audio input/output.
Users
Developed for use in Villages.
Contact Information
Kragen Sitaker wrote the first draft about Low Cost P2P Pagers; it came from discussions with Rohit Khare and Smruti Vidwans, and Dan Gould provided some useful insights as well. Barbara Hohlt told them about TDM power control.
More Information
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