A Case for Custom Silicon in Enabling Low-Cost Information Technology for Developing Regions

1. A Case for Custom Silicon in Enabling Low-Cost Information Technology for Developing Regions Z. Foo, David Devecsery, T. Schmid, N. Clark, R. Frank, M. Ghaed, Y. Kuo, Lee, Y. Park, Z. Renner, N. Slottow, V. Vinay, M. Wieckowski, D. Yoon, C. Schmidt , D. Blaauw, P. Chen, and P. Dutta The University of Michigan

2. Motivation • Recent studies show benefits of information in developing regions • Avaaj Otalo • Mobile-phone-based interactive voice forum • Users found value listening to questions and answers • Digital Green Project • Disseminate agricultural information through video • Large increase in adoption of agricultural practices The University of Michigan

3. Motivation • Talking Book Project • Provide on-demand access to information from local experts • Information pre-loaded onto devices, and re-programmed in field • Farmers showed a significant increase in crop production • Question: Why aren’t these devices more popular in developing regions? The University of Michigan

4. Commodity Devices Not Sufficient • Radio • No replay capability • No indexing • No on-demand information • Voice Recorder • No indexing • Information distribution difficult • Cell Phone • Too expensive - $20-$40 • Running cost too high - $.10-$.30/min. in rural Africa • High power draw • Connection unreliable The University of Michigan

5. Custom Devices Still Not Sufficient • Lifeplayer • Provides data recording, playback, indexing, communication • Costs around $100 • Very large • Talking Book • Similar functionality to Lifeplayer • Scaled way down • Hand-held • Costs between $20 and $35 • 2 - 3 day lifetime on AA batteries Source: lifelineenergy.org The University of Michigan

6. Our Goal Design a custom device: Provide recording, playback, communication, data indexing < $10 Reduce upkeep cost to user Case Study: Redesign Talking Book The University of Michigan

7. Improving The Talking Book • Reduce costs with • Custom silicon integration • Flatter memory hierarchy • Unconventional communication • Will reduce cost to $10 and power by 6x The University of Michigan

8. Use Custom Silicon • Aggressively integrate into custom silicon • Eliminate discrete components The University of Michigan

9. Integrate to Chip • Speaker amp • Voltage regulators • Oscillators • One off chip crystal • Inexpensive, and slow The University of Michigan

10. Memory Hierarchy External NOR Flash Internal Flash Core External SD Card Internal RAM • Old Memory Hierarchy • Goals of new system: • Minimize Costs • Allow for large code bases • Easy for programmers The University of Michigan

11. Minimizing Memories • Use only one NAND Flash • Lower power • Less expensive • NAND Flash • Chips wear out • Not fault tolerant • Slower • Requires software FTL • Uses cache • Improve performance • Reduces flash wear Microcontroller Core Cache Software FTL NAND Flash The University of Michigan

12. Custom Cache • 4-way set associative • 128 KB memory • Cache must use core • Interrupts fetch data • Similar to MMU • Pinned region • Stops critical code from missing • Allows real-time guarantees Microcontroller Core Cache Software FTL NAND Flash The University of Michigan

13. Move Interfaces On-Chip • Push button interface • Expensive - $1 • Requires membrane switch-pad • Mechanical failure • Replace with Capacitive Sensors: • Low chip area • Nearly no cost • Built into PCB • No physical system The University of Michigan

14. Communications The University of Michigan

15. Communications FM Radio • Long range voice distribution • Digital data through RDS sub-band • Download information over night The University of Michigan

16. Communications FM Radio • Replaces USB • Wireless peer to peer • 500Kb/s • Integrated into PCB • Minimal hardware cost Inductive Link The University of Michigan

17. Communications Cell Phone FM Radio • On-demand information download • Directly download voice • Digital data with FSK modulation • Firmware Updates Inductive Link The University of Michigan

18. Bill of Materials - Components The University of Michigan

19. Bill of Materials - Board The University of Michigan

20. Bill of Materials - System The University of Michigan

21. NRE Costs Custom silicon equal COTS 70k units Custom silicon < $10 at 400k units The University of Michigan

22. Power Costs 2 Week battery lifetime on 2 AA Batteries Overall 6x power reduction The University of Michigan

23. Summary • Current devices are not sufficient • Custom silicon: • Gives similar functionality to old Talking Book • Allows entire system on three chips • Reduces all costs to within goals • Custom silicon presents a viable option for large-quantity developing world products The University of Michigan

24. Low-Power Core • Use ARM Cortex-M0 processor • 50MHz core clock • ARM v6m ISA • 32-bit performance • 16-bit instruction size • <10% of total chip energy in active mode • Decodes, timescales, & plays audio real time The University of Michigan

25. Cell Phone Issues Use More Power Stuff about why not good The University of Michigan