Cell Phone Docking Station

1
Cell Phone Docking Station
ECE 345 Project Presentation

• Daniel Finch
• Mihir Shah
• David Johns
• TA Jeff Cook

2
Introduction

• What
• Who
• Where
• When
• Why?

3
What

• Design a system to interface a home telephone
  network with a cell phone.
• Allow incoming calls to a cell phone to ring a
  home network
• Allow audio communications between a cell phone
  and home network
• Provide a seamless environment between the cell
  phone, the home network, and the subscriber line

4
Who, Where, When, Why

• A person wishing to answer cell calls while at
  home without the discomfort of a small cell phone
• A person wishing to charge a cell phone while
  keeping the cells connectivity readily
  available.
• After work, plug the cell phone in the unit,
  charge it up and keep connected.

5
Objective - the original plan

• What we intended to do
• Provide 100 cell phone functionality through use
  of the landline phone

6
BUT

• Motorola has no university support!

7
What we built
SLIC
8
DC / DC Converter

• Uses MC34063A IC
• Inverts 5V to -24V
• Provides reference voltage for SLIC and ringing
  off hook detector

9
SLIC (MC33121) Functionality

• Subscriber Line Integrated Circuit
• Provides Tip/Ring telephone line conversion to
  audio I/O.
• Audio dB level controlled by network attached to
  chip
• Provides hook status of subscriber line

10
Audio Isolation

• 11 Isolation transformers used to reduce
  feedback on audio I/O

SLIC
RXI
TIP
Audio Out
-
-
Audio In
TXO
RING

11
Ring Generator Circuit

• 90V, 20Hz AC signal generated by Cambridge Black
  Magic ring generator (12VDC input).
• Controlled by logic signals from the STAMP and
  component network

12
Ringing Hook Detector

• Custom circuit.
• Provides signal for the STAMP to switch the relay
  from the ringing circuit to the SLIC audio
  conversion circuit.

Rectifier And Reference
Inverter
-24V
12V
-
741
1k?
1k?
20Hz
1.3M?
620?

-
12V
741
-12V
Ring

270k?
20Hz Square Wave (when switched) 0V Else
Unity Gain Follower
-12V
1k?
13
Ringing Generator Output

• Black Magic Telephone Ringing Generator (LS0014)
• 20 Hz AC Sine Wave
• 90 Vrms

14
Ring Output Rectifier

• Diode -Resistor Network
• Remove positive component of sine wave

15
After Unity Gain Follower

• Provides current to drive the ring signal
• Makes sinusoid more of a square wave

16
After Inversion

• Provides positive ring signal for Basic Stamp 2
  to decode
• 20 Hz square wave

17
Cellular Phone Ring Detection Attempts

• Audio out from data connector
• Too small (153mV)
• Too Fast (900MHz)
• Data Bus signals
• Not readable by Basic Stamp 2
• Current Sensing IC
• Didnt work for Vin gt 5V

18
Final Cellular Phone Ring Detection Design

• Audio out from 2.5mm audio jack on phone (20 Hz,
  1V-pp signal)

19
Amplified Cellphone Ring Signal

• Amplified output, compared in Basic Stamp to
  amplitude level
• High amplitude signal (- line noise) ring.

20
Stamp functionality

• Cell ring detection

waitforring2 for reps 1 to 5 pause 20 if in20
then dialtone if in10 then noring totaltotal1 n
oring next if totalgt1 then ring goto waitforring
21
Stamp functionality

• Ringing off-hook detection

pulsin 3, 1, stuff2 ' wait for pickup if
stuff2gt10000 then goback if stuff2lt30 then
goback goto pickup
22
STAMP flow chart
23
The Mechanical Finger

• STA Push Tubular Solenoid
• 5.2V input
• Draws 3A
• 12V / 5A Radio Shack Relay - Basic Stamp 2
  controlled
• Mounted in custom built cradle for cell phone to
  line up with the solenoid.

24
Functionality and Testing

• Test cell ring detection - no erroneous rings
• Test 2 second on, 4 second off ringing - 5 ring
  maximum
• Test hook status functionality
• Test solenoid functionality of send button
• Test audio I/O between cell and land phone, and
  also multiple land phones
• Test cell hang up when phone goes on-hook

25
Challenges

• Contacting Motorola - for both iDen and Microtac
  cell phones
• Cell phone ring detection
• Ringing off-hook detection
• Implementing solenoid
• Debugging noise from SLIC circuit

26
Recommendations

• Dialtone generator
• Databus decoding - Motorola or other brand
• Ability to dial land-line phone using cell line
  connection
• Better cell ring detection (using databus)

27
?Any Questions??Any Comments?

• Where can I buy one?