Wireless Portable USB Hub

1
Wireless Portable USB Hub

• ECE 445 Senior Design Project
• Group 13 Mathews Antony, Charles Hsieh and
  Steven Li

2
Engineering Considerations

• Must interface with devices compliant with USB
  Standard 1.0 and 1.1
• Max throughput must be around 12Mbps
• Signal must travel uncorrupted for a range of 4m
  
• Current drawn from Vbus must be less than 500mA
• System must be battery powered

3
Consumer Considerations

• End product must be in the form of 2 dongles
• It must follow a plug and play model, allowing
  the customer to connect and disconnect
  effortlessly
• The product must retail for less than 30
• Universally adaptable to all of the consumers'
  USB devices

4
USB Standard

• Uses 4 shielded wires
• 2 power (5V and GND)?
• 2 differential data lines (D D-)?
• Uses a Tiered Star Topology
• 127 Devices can be connected to a single USB bus
• Power to each device can be monitored
• Both high speed (12 Mbps) and Low Speed (4 Mbps)
  are supported
• Dynamically loadable and unloadable drivers
• User plugs in device
• Host detects device
• Host interrogates the new device
• Host loads the appropriate driver
• Device is ready to be used

5
Different Ways to Utilize USB Signal

• I2C
• RS232
• SPI

6
I2C, RS232, SPI
7
Design Decision 1 Which Bus Architecture?

• Choose SPI
• Why?
• Has a Master/Slave relationship similar to USBs
  Tiered Star Topology
• Optimized for Point to Point Communications
• Full Duplex Communications
• Capable of much higher throughput when compared
  to other Buses

8
Different Ways to Transmit Wirelessly

• Ultra Wide Band
• WiFi (802.11 b)?
• Infrared (IrDA)?

9
UWB, Wifi, and IRDA
10
Design Decision 2 Which Wireless Architecture?

• Choose Infrared (IrDA)?
• Why?
• Cheap! (4 per transceiver module)?
• 16Mbps Max Throughput
• Very low power consumption (300mW)?
• Deals very well with EMI
• All other architectures were either still in
  development phases or too expensive

11
Block Diagram of 3rd Initial Design
IR-PIC Interface
USB Bus Signal
IR-switching MUX
0
TxD
VFIR Transceiver
B-Style USB Plug
PwrCntrl-PIC Interface
Microchip PIC Microcontroller
1
sel
Port Power EN/Dis
USB Power Controller
SCLK
Over Current Flag
RxD
Gnd
Bus Active
Periph-PIC Interface
sel
D
D-
SCLK
USB Interface switching MUX
0
USB Peripheral Controller
1
12
Software Overview
Pwr Cntrlr Flip Sw

• Configure IR Module and/or other modules
• SPI programming sequences
• Control dynamics of overall circuit
• Handle Device Reset
• Monitor Bus activity flag
• Flip Power Controller Port Enable/Disable flag

No
Yes
Load Prog Sequences to output buffers
Shift buffers to read MSB
Output MSB on lines with SCLK
Last Sequence Programmed?
No
Yes
Is there Over Current?
No
Yes
Turn Off Load Port
Turn On Load Port
13
1st Plug-in Run

• The IR module did not turn transmit
• Potentially multitude of problems exist
• Outline of IR Module Trouble-shooting
• Software check programming sequence and timing
  specifications
• Hardware check pin voltages and diode voltages

14
Testing the IR Module

• Setup Time 10us

15
Testing the IR Module

• Hold Time 100us

16
Testing the IR Module

• Input Sequences
• Register0 Main Control Register
• 01-1-0000-010-1-11101000-00
• Register1 IR Transmission rate
• 01-1-1000-010-1-01000000-00
• Register2 IrED Current
• 01-1-0100-010-1-00000100-00

17
Testing the IR Module

• Reading from programmed registers

Register 0 data 11101000 Register 1
data 01000000 Register 2 data 00000100
18
Waveform Testing Conclusion

• SPI timing specifications met
• Able to program registers and read correct data
  bits from the same registers
• Discrepencies Found
• To Enable All, Main Control Register must be set
  to 0b11101000. The suggested Main Register value
  is 0b11110000.
• To read from registers the input sequence must
  be 0b010000001001111111111100 (this sequence
  reads from reg0) and it is not clear from the
  datasheet this was ever mentioned.
• The RxD line does not echo TxD line when in SD
  mode.

19
IR Module Hardware Testing
Pin Voltages on tfdu8108

• Specs as indicated by Vishay
• Pins 1,4,6, and 7 voltages should be near Vcc
• Diode Voltages from pins 27 to Gnd (pin 8) are
  around 0.5V

Diode Voltages on tfdu8108
20
Conclusion of Hardware Tests

• Pin voltages normal indicates our supporting
  circuits for the IR module is correctly built
• Diode voltages normal indicates our IR module do
  not have burned internal connections
• Other Possibilities
• Try Different VFIR manufacturers?

21
Power Controller

• Battery Life 625mAh
• Converts 9VDC to 5VDC
• Four outputs, each supply 5V
• Current Limit 500mA max
• Overcurrent Protection _at_ 380mA
• Overtemperature Protection _at_ 140C

22
Power Controller Battery Life

• Total design current grain 80mA
• Power Controller 8mA
• IR Controller 18-20mA
• PIC Microcontroller 20mA
• Theoretical Max Current 500mA
• Actual Max Current 350400mA

23
Power Controller Battery Life (Cont.)

• Battery Life Expectancy
• Without Load
• 625(mAhrs)/80(mA) 7.81Hrs
• 7 Hours 48 Minutes
• Max Current
• 625(mAhrs)/500(mA) 1.25Hrs
• 1 Hour 15 Minutes
• Recommended Current
• 625(mAhrs)/(350mA) 1.79Hrs
• 1 Hour 48 Minutes

24
Power Controller Output

• Vmax 5.07V
• Vaverage 4.98V
• Vmin 4.89V
• Vripple 0.09V

25
Power Controller Output

• 63 Test Cases
• MOSFET or without MOSFET
• 5V LDO or without 5V LDO
• Charge capacitors in the LDO
• Best setup
• Vext 9V
• 5V LDO Enabled
• Charge capacitance of 0.01uF
• Current
• Best Case
• Iout 400mA
• Most cases
• MOSFET Disabled, LDO Enabled
• Iout 222mA
• Worst Case
• MOSFET Disabled, LDO Disabled
• Iout 0mA

26
Power Controller Overcurrent/Overtemperature

• Current gt 380mA Overcurrent
• Vovercurrent 0V 1.51V (ON)
• Vovercurrent 1.51V 3.3V (OFF)
• PIC Microcontroller
• Control the overcurrent condition
• Turn off the output when the condition is on

Vmax 250mV Vaverage 250mV Vmin 235mV
LED of Power Controller
LED of Overcurrent Condition
When the overcurrent condition is on
Overcurrent output waveform
27
Power Output USB Devices Demo

• Plug and Play
• Correctly Power up the USB devices and provides
  its appropriate functionality

28
PCB Adapters Modular Design and Testing
VFIR Controller
Peripheral Controller
Power Controller
29
Improving Our Design

• What needs to be changed?
• Need USB Bridge Controller
• IrDA Encoder/Decoder
• Programming Sequence Externally Selectable (for
  debugging)

30
Putting it all together
Small Overall Package Size
31
IrDA System Improved Design
IR-switching MUX
0
TxD
VFIR Transceiver
B-Style USB Plug
Microchip PIC Microcontroller
1
Vbus
sel
Port Power EN/Dis
USB Power Controller
D
D-
SCLK
Over Current Flag
RxD
Gnd
Bus Active
IrDA Decoder
IrDA Encoder
sel
USB Bus Signal
D
USB Interface switching MUX
0
USB Peripheral Controller
USB Bridge Controller
1
32
IrDA-dongle Design Prototype
Power Controller
Overall IrDA-system
VFIR Module, Peripheral Controller, PIC
Microcontroller
33
Questions?