Featherweight Electronic Book
for
Rural Education
Rajkumar Singh Parihar
BITS Pilani
Mentors
Kentaro Toyama Vibhore Goyal
MSR India
Outline • Overview of TEM
• Overview of Featherweight Electronic Book
• Motivation and Innovation behind Design
• Block Diagrams and Various Alternatives
• Basic Building Blocks of Design – Microcontroller
– MMC and Interfacing
– Key Pad and Interfacing
– PWM signal to Audio Generation • 5th Order Active Low Pass filter Design
• Audio Amplifier
• Speaker interfacing
• Future Directions and Improvements
Technology for Emerging Markets
Understand (potential) technology users in emerging-market countries – E.g., urban middle-class
– E.g., rural entrepreneurs
Invent new technologies and make suggestions on policy
Contribute to growth in emerging markets and to socio-economic development of poor communities worldwide
Government-sponsored lunches
at a rural school in Tamil Nadu
Goals
Featherweight Computing??
• Devices which do a small calculation for their functioning
comes under this category.
• Technologists generally call them “Digital Manipulative”.
why??
• The Motivation and idea behind the approach is to create
a new capability in object without changing Basic overall
look and architecture. (i.e. create a talking capability in a book
with reprogramming over time so that it can read its text also.)
Smart Computational Toys
• “Smart toys combine the best of the two worlds – traditional toys and the power of computers and electronic chips. Experts predict that almost every toy will be powered by interactive technology in near future”.
- Herman D’Hooge and team, smart toys: Brave new world
• “Researchers are now exploring ways of adding computational capabilities to everyday objects ranging from notepads and desktops to eyeglasses and shoes”.
- weiser,M.(1991). The computer for the 21st century. Scientific American 265,3,94-104.
• “Our goal in designing new “digital manipulatives” is to make a new set of concepts salient for children. Our basic strategy is to embed computational and communications capabilities in traditional children’s toys”.
- Mitchel Resnick & team at MIT media lab. Digital manipulatives: New Toys to think With
Featherweight Computing
• Anticipated target user is from remote rural areas. They may be…
– Illiterate or semi-literate adults
– Children
– Physically disabled (e.g., blind)
– Economically poor
– Without access to consistent electrical power
• Characteristics of featherweight computing:
– Serves single purpose well
– Very cost-effective
– Simple user interaction
– Low power
– Robust, highly reliable
Actual User
Kids Illiterate
Adults
Blind People
Electronic Book
• Target customer – Strong interest in improving quality of life through increased literacy and
information.
– Need effective ways to access information (e.g., health, hygiene, agriculture, etc.) in local languages.
• Solution: electronic book – Designed for education
– Could cost US$20-30
– Extends standard “book” format; touching book causes audio playback
– Uses 4 AA batteries
– Strong plastic encasing
• Existing products – LeapFrog LeapPad
– Fisher-Price PowerTouch
Our Goals at MSRI
• The TEM group is interested in experimenting with electronic books in rural India.
• Existing products do not allow flexibility to create local content.
• We will create an electronic book where we have the flexibility to change the content ourselves.
• If we have time, we would like to experiment with our electronic book and try it with children in Bangalore slums.
Generic Block Diagram: E Book
Micro-controller
Digital Data to
Analog Signal
Converter
Touch
Pad
Storage
Device
Page
Decoder
Speaker
Internal
RAM
Different Possibilities that
We Considered
ATmega
162
Serial
DAC
SD
MMC
Speaker
ATmega
162
PWM
(LPF)
capacitance
Sensor
USB
drive
PIR
Sensing
Tech Speaker
ATmega 162
LPF
NCP
MMC
Speaker
ATmega
162
Parallel
DAC
MMC
card
ADC-08 Speaker
4x4
Keypad
8x8
Keypad
4x4
Keypad
Audio
Amplifier
1 2 3 4
5 6 7 8
9 0 A B
C D E F
(1) (2)
(3) (4)
Optimized Block Diagram for
Final Implementation
MuC
Key Pad
MMC
LPF
(5th order)
Audio
AMP
Speaker
XTAL
Gnd
Gnd
Vcc
Vcc
Why did we choose?
1. Cheap and Cost Effective
2. Components are Easily available
3. Easy interfacing of Blocks
4. Easy programming for
configuration
1 2 3 4
5 6 7 8
9 0 A B
C D E F
Basic Building Blocks (Components)
• MuC ATmega 162
• MMC NCP 128MB
• Keypad 4x4
• LPF 5th Order using
LM324
• Audio Amplifier LM386
• Speaker 8-ohm
Cost (INR)
60/-
200/- (16MB)
20/-
10/-
10/-
20/-
Total 320/- (INR) This Estimation is valid for production of 1000 Such books.
Flow Diagram (E Book)
Power ON
Touch
An object on
PAD
Audio
Feedback
POWER
ON/OFF
Wait for
Next INT
ON
OFF
Good Bye
Power ON
All device
•I/O port DIR_INIT
•MMC_INIT
•Wait for INTR
Keypad
PRESS?
•Calculate ADD (Size, CLUS) of file
•Read SEC 1 by 1 into BUFF
Take A PCM Sample from BUFF
Generate PWM equ. to DIGI_DATA
FILE_SIZE = FILE_SIZE - 512;
Y
N
FILE_SIZE?
0 1
Flow Chart of System Events
User Interaction and Responses from Device
Microcontroller : ATmega-162
• Computer on a chip – CPU core
– Memory (ROM and RAM)
– Digital I/O ports
– Easy interfacing
Key features: • High performance
• Low power consumption (2.7- 5V)
• High code density (16KB)
• In-system development
• SPI ( MMC Interfacing )
• 2 USARTS (RS-232 Interfacing)
• PWM Signal Generation Capability
• 3 Programmable Timer
MMC • Multimedia card
– Storage for audio data
– Portable
– Removable
• Advantages: – Moderate cost
– Robust
– Small size
– Serial Peripheral Interface
• 4 signals for interface
– Data in
– Data out
– Clock
– Chip select
1
2
3
4
5
6
7
5.6K
20
21
AT
me
ga
162
1
40
MuC
/SS
MOSI
MISO
SCK
RST
OC1A
PA
PC
PB
PD
22pF
16MHz
Vcc
XTAL1
XTAL2
MMC
User Interaction :Touch Keypad
• Allows user interaction with device
• Based on contact or pressure
• Considered: – IR touch panel
– Capacitance touch pad
– Keypad(4x4, 8x8)
• Advantages: (4x4 keypad) – Inexpensive
– Easy to interface
– Readily available
– Sturdy
4x4Keypad
1
4
7
A
8
0 B
9
3 F
E
2
D
C
5 6
Keypad Interfacing : How It Works?
All the rows are grounded
and columns are scanned
until one of them is zero.
One row is high at a time
and all the columns are
read.
For Some Combination all
the column will become High.
The combination of column
read (0111,1011,1101,1110)
and Value sent to Row
(1000,0100,0010,0001)
will give a unique value
which can be easily
mapped into
“unique Key PRESS”.
Schematic for keypad interfacing
4x4
Keypad
1
4
7
A
8
0 B
9
3 F
E
2
D
C
5 6
20K(each)
20
21
AT
me
ga
162
1
40
MuC
/SS
MOSI
MISO
SCK
RST
OC1A
PA
PC
P
B
P
D
20K
22p
F
16MHz
Vcc
XTAL1
XTAL2
What is a PWM Signal?
• When communication by pulses was introduced, the
Amplitude (PAM), Phase (PPM) and Pulse width (PWM)
become possible modulation options.
• In PWM the duty cycle of each pulse of a symmetric
Square Wave is modified to proportional with the audio
sample Value at that Instant.
• How do we Implement that?
PWM Signal: Audio Generation
PWM Signal to Analog Waveform:-
1. A simple RC circuit, fourth-order low pass active filter and audio amplifier are used to convert the PWM signal into audio signal.
2. RC circuit and Low Pass Filter is used for harmonics and carrier frequency generated by PWM signals. The RC circuit is for attenuation. It prevents the saturation of the low pass filter and the audio amplifier
3. The audio amplifier will drive the speaker to generate the audio.
The output sound quality is as good as an AM radio.
Active LPF: PWM signal to Audio
Analog wave Generation
LOW PASS
FILTER
Audio
AMPLIFIER
PWMO
To LPF
PWMO
33K + +
+
5th Order LOW Pass Filter
LM324
850p
F
850pF
850pF
850pF
46K
850pF
33K
68K 56K
Vout
200uF
10ohm
LM386
+
50nF
2 4
5
3
6
Vin Vout
Complete Schematic (All in One)
• Include all the library files
• MMC initiation
• FAT16 Implementation
• 4x4 Keypad press detection function
• Reading the clusters, sector by sector
• PWM signal for each byte
• Check the size of file and Data Read
• Read the cluster until the data read==file size.
• Wait for a new key press.
+ +
+
5th Order LOW Pass Filter
LM324
850p
F
850pF
850pF
850pF
46K
850pF
33K
6
8
K
4x4
Keypad
1
4
7
A
8
0 B
9
3 F
E
2
D
C
5 6
20K(each)
1
2
3
4
5
6
7
5.6K
20
21
AT
me
ga
162
1
40
MuC
/SS
MO
SI
MIS
O
SCK
RST
OC1A
PA
PC
P
B
P
D
20K
22p
F
16MHz
Vcc
XTAL1
XTAL2
200uF
10ohm
33K
56K
LM386
+
50nF
2 4
5
3
6
MMC
Program Structure:
Future Improvements:
• Keypad can be replaced by a better and sophisticated
Touch pad (i.e. Power Touch Pad).
• To improve the audio quality of sound a Low pass filter
IC can be used in place of LPF made of Discrete
components.
• MMC connectors will make the transfers of files from PC
to board Easy.
• Using MP3 decoder files directly can be stored in mp3
format which is most popular because of it’s smaller size
and good voice quality. Right now only 8-bit PCM wave
format files can be used.
Analog to Digital Recording and playing Chain
ADC
Continuously varying electrical energy is an analog of the sound pressure wave.
Microphone converts acoustic to electrical energy.
ADC (Analog to Digital Converter) converts analog to digital electrical signal.
Digital signal transmits binary numbers.
DAC (Digital to Analog Converter) converts digital signal in computer to analog for your headphones.
DAC
Basic Digital Audio Concepts
• Sampling rate – Number of sample taken of a signal in a given time
(usually one second)
• Bit depth – Describes the accuracy of the audio data
• Channels – E.g. Stereo has two channels
• Bit rate – Measured in kilobits per second (Kbps) is a function
of the bit depth and sampling rate
Basic Wave File Layout
Chunk ID "RIFF"
Chunk Data Size
RIFF Type ID "WAVE"
Chunk ID "fmt "
Chunk Data Size
Chunk Data Size
Sample Format Info Chunk ID "data"
Digital Audio Samples
52 49 46 46 9e a6 03 00 57 41 56 45 66 6d 74 20 RIFFž¦..WAVEfmt 1e 00 00 00 55 00 01 00 22 56 00 00 a0 0f 00 00 ....U..."V.. ..
01 00 00 00 0c 00 01 00 02 00 00 00 68 00 01 00 ............h.. 71 05 66 61 63 74 04 00 00 00 be 1e 14 00 64 61 ..q.fact....¾...
74 61 60 a6 03 00 ff f3 40 c4 00 13 c1 51 ed b9 data`¦..ÿó@Ä..
Chunk ID
Chunk
Data Size RIFF Type Chunk ID
Chunk Data Size
16 + extra format bytes Compression
code Number of
channels
Sample rate Average bytes
per second
Block align Significant bits
per sample Extra format bytes
data chunk size
Sample Data
Chunk ID
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