Re: NTLK Using a Stowaway Keyboard with a Newton

From: Grant [Stuck On The Grid] Hutchinson (
Date: Tue Aug 01 2000 - 00:05:46 CDT

On 30/07/2000 11:53 AM Michael J. Hu▀mann wrote:

>The Stowaway can't be a USB device for one reason: on the USB bus, there
>is always exactly one host controller and up to 127 peripherals. If the
>keyboard was a USB device, either it or the Visor would have to be the
>host controller, but the Visor can't be the host because it is plugged
>into a Mac's or PC's host controller itself, and the keyboard can't be a
>host controller because it is powered from the Visor. Needless to say,
>just plugging one USB peripheral into another won't work.

According to the pinout diagram for the Visor cradle connector, there are
pins specifically marked as USB Data + and USB Data -. The datasheet
states that these two pins "implement the USB signaling protocol for
communicating with a USB host, such as a PC or a Mac." I believe this to
mean that since a Mac or PC with a USB port is a USB host (or hub) and
not a USB peripheral, the keyboard (or other device connected to the
Visor port) does not need to be USB itself. The Visor cradle acts like an
adapter, not as a USB device.

There are also standard TTL level asynchronous serial communication pins
marked RXD and TXD (for Receive Data and Transmit Data) on the connector

For all the gory cradle connector details, see chapter 2 of the
Development Kit for Handspring Handheld Computers. I have a copy of it
posted to this page of my site.



Grant Hutchinson Interface Considerations & Toys

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