Registered: Dec 1999
Location:
Posts: 1

Here is the discussion I spawned on a ham radio discussion list. It involved using the Visor to control a small portable handheld (ham) transceiver. Apparently the radio requires RS-232 signals to input signals it will recognize andx respond to. My (novice) problem is that I don't know enough about RS-232 to know if I can make the Visor do it (in other words, I am not sharp enough to decipher the nuances of the Developers Manual). Maybe one of you can help me out, directly ([email protected]) or on this list. I will cross-post to the other list if you want, since it is a 'closed' list.

Thanks - Mark (N4OGL)
===================
Here's where we are so far - my reply is to another ham on the list (Daniel). To decipher the buzzwords, the TH-D7A is the brand of radio I'm trying to interface.

Hi Daniel,

I have the Visor USB Cable (found at http://www.handspring.com/products/cradlescables.asp). Is that what you mean by "modem cable"? Or is there an alternative source? I have the USB cable, and just wondered if I can modify it by cutting the end off and putting on the right plugs and a power source (as shown on www.pocketaprs.com page, regarding the 9v battery addition to the Visor cable).

Mark

> -----Original Message-----
> From: Lavoie Daniel[[email protected]]
> Sent: Wednesday, February 23, 2000 12:22 PM
> To: 'TAPR Hot Technology APRS'
>
>
> Mark,
> I once spoke to HandSpring regarding the Visor's serial port and basically
> the Visor is not a true RS-232 device because the port signals are 0-5V and
> not +12v to -12v required by the TH-D7. The only way to get a true RS-232
> signal is to add a level converter or buy the Visor's modem cable (if you
> can find one) which has a built in converter.
>
> > ----------------------------------------------------------------------
> >
> > Subject: VISORs, TH-D7A, PocketAPRS and "Pin 2"
> > From: "Mark Keiser" <[email protected]>
> > Date: Tue, 22 Feb 2000 16:05:00 -0600
> > Hi HT-APRS community,
> >
> > I'm ready to play with my VISOR and pocketAPRS. I saw the
> > interfacing comments
> > for the Visor on the web page, and I
> > wanted to send this excerpt from the Developers manual,
> > because (frankly
> > I may be over my head here.
> >
> > On the Visor page (http://www.pocketaprs.com/visor.html), it
> > said to insulate
> > Pin 2 from the stand ("...there is a way
> > to "fool" the Visor serial stand into talking to RS-232
> > devices without
> > finding a way to separately power the stand. To
> > do this simply involves insulating Pin 2 ("KBD") from the
> > stand..."). I
> > have a Visor-connector-to-bare-wire cable
> > (after cutting off the USB connector), and I wonder whether
> > you could interpret
> > the following excerpt as grounding Pin 2
> > to the ground in the connector as fooling the Visor, and
> > getting it to
> > accept from and provide commands to the TH-D7A.
> >
> > If anyone could help me understand this, and whether this
> > will work to
> > drive a TH-D7A, I would be grateful. My goal is
> > to get the GPS Springboard module for my Visor, and then just
> > have a
> > TH-D7A and the Visor with an internal
> > module for GPS as my portable APRS station.
> >
> > 73s de N4OGL
> >
> > Excerpt from the Visor Developer's Kit, page 72:
> >
> > The handheld platform supports character input from an
> > external keyboard
> > or pen-based device through the Cradle
> > Connector located at the bottom of the handheld device. Pin 2
> > of the eight
> > -pin Cradle Connector is the keyboard detect
> > pin (KBD*). Grounding this pin indicates to the handheld
> > processor that:
> > 1. A keyboard or other remote UI device is present on the
> > Cradle Connector
> > and
> > 2. Incoming serial data packets on RXD (pin 1 on the Cradle
> > Connector)
> > should be interpreted as described by this
> > document.
> >
> > Note that the Cradle Connector does not include hardware
> > signaling for
> > buffer overflow conditions within the handheld
> > device. Therefore the maximum recommended serial transfer
> > speed to the
> > handheld device is limited to 9600 kbps.
> >
> > Remote UI is supported in all existing versions of PalmOS.
> >
> > 3.1 Remote UI Packet Description
> >
> > As long as pin 2, KBD*, on the Cradle Connector is held low,
> > the handheld
> > will receive incoming data packets on RXD and
> > interpret them as Remote UI Packets. Remote UI Packets have
> > three sections:
> > a header, a body, and a CRC as shown in
> > (the) Figure.

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Registered: Sep 1999
Location: Hoboken, NJ, 07030
Posts: 105

I'm no expert but I believe that the USB cable will not do what you want.
To access the RS232 portion of the Visor port you will need to connect to different pins. You might want to check out the thread on converting serial cradles to USB. Also note, for a standard RS232 signal you will need to amplify the signal lines.
Best of luck with your project, let me know if you get it to do graphitti to code conversions :-), I've always wanted to be a ham but haven't had time.

Registered: Dec 1999
Location: Connecticut USA
Posts: 2682

The Visor "speaks" TTL on the RX and TX pins (1 and 8 on the Visor connector). Therefore, a TTL to RS232 converter needs to be used. I believe that the serial cradle has one built in and would probably work for you. A null modem adapter may be needed but I'm not sure.

There are some threads here from some folks who have successfully connected to an external modem... should be the same concept I would think.

------------------
MarkEagle - Ice is nice!

[This message has been edited by MarkEagle (edited 02-23-2000).]