BT Adapter

Features

• Bluetooth interface
• USB interface (?)
• On-board rechargeable battery
• Charges via USB port (rate set by port type? If USB charger, assume 500ma)
• LEDs indicate battery charge status, USB power, BT module searching, BT module connected
• Mini-B USB connector

Reasonable intelligent power: If powered by USB, BT module is always on. If powered by battery, push-button switch turns BT module on/off, and automatically turns off after some period of inactivity from the BT module TXD line. Unit has low battery warning (flashing LED), and automatically shuts off when the battery goes below a certain voltage.

Theory

• If connected to USB port

• Attempt to get 500ma configuration
  • Charge battery at 500ma (minus overhead)
  • Assume operating in CDC mode
  • Remains on while attached to USB
  • If unplugged, powers off
• If only 100ma configuration available
  • Charge battery at 100ma (minus overhead)
  • Assume operating in CDC mode
  • Remains on while attached to USB
  • If unplugged, powers off

• If USB charger detected

• Charge battery at 500ma
• If button pressed
  • Power on RN-41
  • Remains powered on
  • If power removed, auto-power off after inactivity

• If no USB port or charger

• If button pressed
  • Power on RN-41
  • Auto-powers off after inactivity

Indicators, etc

• Blue RN-41 LED

• 100ms on, 900ms off indicates waiting for association
• 200ms on, 200ms off indicates connection open
• Off indicates RN-41 disabled

• Green USB LED

• 100ms on, 900ms off indicates 100ma profile
• 500ms on, 500ms off indicates 500ma profile
• Off indicates no USB connection

• Red charging status LED

• 200ms on, 200ms off indicates low battery
• 100ms on, 900ms off indicates charged battery
• Solid indicates charging
• Off indicates no charger availability (and no low battery)

Parts

• Roving Networks Bluetooth module

• Product page
• BlueSMiRF Schematic
• RN-41 Command Set
• RN-41 Datasheet

• Linear Tech LPC3455 LiPo battery charger

• Product page
• Datasheet

• 2600ma 3.7V Li-Ion battery

• Product page
• Technical information

• Maxim MAX4906F USB Switch

• Product page
• Data sheet

• Microchip PIC18F26J50 (?)

• Product page
• Datasheet

• Fairchild FAN3989 USB Charger Detection

• Product page
• Datasheet

Resources

• USB Specifications
• FindChips.com