How to Connect Your Handspring PDA to a Serial Network

Visor® handheld computers by Handspring® are unique in that they have only TTL levels available on the handheld to cradle connector. They use level shifting circuitry inside the serial cradle or cable to reach RS-232 compatible levels of ±6V.

This requires lines DTR and/or RTS (pins 7 and 4 on a male DB9 and pins 8 and 6 on a DB9 female) as high inputs to power the level shifting circuitry. If at least one of these lines is not available or high there will be no signals available on the DB9 connector.

Visor, Visor Deluxe, Visor Neo, Visor Prism, Visor Pro and Visor Platinum handhelds by Handspring use the same serial synchronization cradle and cable. However, to recharge the Prism and Pro, you will need a special cradle that supplies power to the recharge pin. The Visor Edge requires its own serial cradle and cable, too.

The Treo series also has its own cable and cradle. The cables, available from Visor dealers, bring the Visor's serial port out to a DB9 female connector, configured as a DCE device. This allows the cable to be connected directly to a PC's serial port, which is configured as DTE. Only lines TD and RD are supported for communications. Lines DTR and/or RTS are required as high inputs to the serial cradle or cable to ensure proper RS-232 voltage levels of ±6V. The cradles for these handhelds are not compatible with any other handheld. A USB cradle or cable for these handhelds cannot control another USB peripheral device.

Click here for a comprehensive connection chart for all of these and other PDA's.