I built a dual I/O (USB & RS-232) cradle for my Compaq iPAQ PocketPC to better enable my development work, as well as to enable me to use an external keyboard while leaving the iPAQ in the cradle. I recently purchased the Targus Stowaway portable keyboard and was very disappointed to discover that it cannot support the iPAQ fully loaded with a PC Card Expansion Pack.
The dual cradle is based on the original design by David Landais, although I started out with a USB cradle and grafted RS-232 onto it.
Tools
- Torx screwdriver (T6 size)
- fine round file or sharp knife (I used a Dremel rotary tool with a 1/8″ hole drill bit)
- soldering iron & solder (you need a very fine tip)
- heat gun, matches or a lighter
- wire cutter/stripper
- magnifying glass
- continuity tester (I used a Sperry DM-5300 digital multimeter)
Materials
- shrink tubing or electrical tape
- Compaq iPAQ USB Cradle (part #176481-B21)
- female DB9 connector
- 9-conductor cable with mesh shielding
For the last two items, I cannibalized a retired HP200LX serial sync cable. If you want to waste perfectly good money, you could cannibalize Compaq iPAQ Serial Autosync Cable (part #191008-B21) for this purpose.
Most of these tools & supplies can be found in your nearby electronics store such as RadioShack.
Instructions
- Unscrew the four T6 screws on the bottom of the cradle
- Detach the cradle bottom from the top (beware the springs inside)
- Remove the tiny PCB from the cradle
- Strip the 9-conductor cable and the individual wires inside it
- With the continuity tester, figure out which wires in the cable connect to which pins in the DB9 connector
- Solder each wire to the respective pin on the exposed backside of the tiny connector on the PCB. Follow the wiring diagram below
- Test each connection all the way through
- Use the round file, sharp knife or drill to expand the I/O cable opening in the back of the cradle so that the additional cable fits snugly out of the cradle (see the picture above)
- Re-assemble the cradle using the four T6 screws (remember the springs)
- Test both USB and serial connections by configuring ActiveSync to only use one of them at a time
Electrical Connections
| DB9 | CON2 | Signal | Description |
|---|---|---|---|
| 01 | 06 | DCD | RS-232 Data Carrier Detect |
| 02 | 04 | RXD | RS-232 Receive Data |
| 03 | 05 | TXD | RS-232 Transmit Data |
| 04 | 07 | DTR | RS-232 Data Terminal Ready |
| 05 | 09 | SGND | RS-232 Signal Ground |
| 06 | 01 | DSR | RS-232 Data Set Ready |
| 07 | 02 | RTS | RS-232 Request To Send |
| 08 | 03 | CTS | RS-232 Clear To Send |
| 09 | 08 | RI | RS-232 Ring Indicator |
| shell | 10 | GND | Power Ground |