I have searched around this website but have found no helpful information regarding the serial port of the Treo 300.

- What is the pin out?
- Do I need an external power supply to power this port?
- Are there API's out there that will allow my application to read data from this port?

Thanks for any information.

-Henk
dutchman1234 at hotmail dot com

You need an external power source for the Treo serial port (or any Handspring PDA). They get power from the computer they are connected to.

The pinouts should be:
Pin Name I/O/P1 Function
1 RXD I Receive Data
2 TXD O/P Transmit Data/Power
3 No Connect GPIO to internal battery pack
4 HS2* I Serial Cradle Detect
5 HS1* I HotSync Interrupt
6 GND P Ground
7 USB_D- I/O USB Data Negative
8 USB_D+ I/O USB Data Positive
9 DQ I/O 1-wire communication pin
10 PACK+ P a1 Battery Positive Terminal
11 PACK+ P a1 Battery Positive Terminal
12 GND P Ground
13 GND P Ground
14 VDOCK P Cradle Power (charging)
15 VDOCK P Cradle Power (charging)

I had a hard time finding the Treo technical reference guide (which used to be downloadable from Handspring's web site), so when I finally found it I put a copy of it on my web server, here:

http://www.burtonsys.com/handspring_treo_techref.html

The TechRef is circa 2002, and it covers the Treo 90/180/180g/270. It doesn't cover the Treo 300, but the 300 is very similar to the 270 (but PCS/CDMA instead of GSM), and the pinouts are identical (see p.50 of the TechRef).

Note that the Treo's serial lines are TTL (5v) levels, not RS-232. If you need RS-232 levels then the easiest solution is to buy a Treo serial hotsync cable on eBay.

I hacked up a serial hotsync cable to make this connector:

http://www.burtonsys.com/treo_connector.jpg

The red wire is RxD.
The orange wire is TxD.
The black wire is ground.

The circuitry that you see on the little PCB is the TTL/RS-232 voltage level conversion circuit that hides in the connector housing of a serial hotsync cable. That big silver thing in the middle is the hotsync push-button (which should tell you which side of the connector we're looking at in the photo).

For my application I didn't need the RS-232 level translation, so I just cut the traces and used wires soldered directly to the edge connector. (Soldering those tiny connections is challenging, BTW!)

-Dave
dave314 at burtonsys.com