Subject:
|
Re: Wireless communication with the Handyboard
|
Newsgroups:
|
lugnet.robotics.handyboard
|
Date:
|
Fri, 16 Apr 1999 06:28:59 GMT
|
Original-From:
|
Ryan Hinton <hintonr@et.byu.eduAVOIDSPAM>
|
Viewed:
|
1121 times
|
| |
|
|
We just finished using the same comm. boards for our senior project,
so maybe I can help a little.
On Fri, 16 Apr 1999 DjKOz97@aol.com wrote:
> Hello,
>
> I've been very busy trying to communicate with the Handyboard via a
> wireless link ( HP Development kit form Linx Technologies). I have
> run into a slight problem-
>
> The kit comes with 2 "development boards" - each contains a
> transmitter, receiver, and an antenna. Linx provides software to
> establish a simplex communication between 2 computers ( which means
> only one transmitter/receiver pair are used at a time). In order to
> communicate with the handyboard, I'll need ( I think ) at least a
> two way half duplex transmission protocol.
>
> Here is the problem: In the current set-up, all four Linx Tx/ Rx
> modules are enabled at the same time. They all transmit at the same
> frequency, which causes a problem. Data sent to the transmitter on
> "Board 1" is immediately picked up by the receiver on the same
> board, having a loop- back effect. The problem can be solved by
> transmitting and receiving at two different frequencies, which is
> not too difficult, considering that Linx provides a dip switch to
> select between 8 different frequencies.
> Having explored this solution, however, I keep getting the following
> message whenever I try to run IC via the wireless link:
>
> Looking for prompt, received 255
> Synchronizing with Board....
> The number "received" varies with each successive synchronization
> attempt.
One interesting phenomenon we noticed was that we received random
noise at the receiver when the transmitter wasn't on. However, when
the transmitter was powered up, the receiver was quite consistent--and
mostly noise-free.
> So here is the question:
> On the Handyboard side: Is it possible to somehow monitor a pin on
> the 68HC11 to see whether it is transmitting or receiving? I plan
> to use this pin to enable only one Tx/ Rx pair at a time. (The Linx
> Tx/ Rx modules have a power down pin for this purpose).
>
> On the PC side: Could I use the DTR, CTS, and RTS serial pins to perform the
> same function?
> I am confident that the wireless link works in the simplex mode, since I was
> able to transmit an analog audio signal from a Walkman to a Stereo!
> Any thoughts on the matter would be highly appreciated.
That sounds along the right lines of thinking, but the problem to me
seems to be coordination. You're going wireless to remove the direct
link, right? But to use a pin from the Handyboard to enable only one
of the TX/RX pairs at a time would require a wire connection back to
the PC, true?
To me, it appears one of your more important issues is multiplexing
the serial line to/from the Handyboard/PC. You didn't mention this in
your e-mail, but it seems fairly obvious, so perhaps the omission was
purely typographical. Anyway, you'll need a mux somewhere to choose
between the serial line from the RX board and to the TX board. (As
far as I know, anyway, IC can't transmit/receive on two different COM
ports on the PC, nor push/pull serial data from different sources on
the Handyboard.)
Once you've established all the correct lines, voltage levels,
etc. (we had a hard time with this...), you'll need select lines for
the mux on each end. Now, we didn't play with this, but I remember a
RSSI signal from the RX boards that, if I understand correctly, was
supposed to indicate a detected carrier--i.e. it's receiving
something. It seems you should hook this up as the select line to
your mux. That way the serial line defaults to transmit, but should
switch over to the RX board when it's receiving data. You'll have to
check the documentation on the Linx boards, but this may be your
ticket.
Incidentally, don't forget to use a null-modem cable between the Linx
boards and the Handyboard. This simple oversight cost us (me) a great
deal of time and frustration.
-------------------
Ryan Hinton ;)
ryan_hinton@byu.edu
http://www.et.byu.edu/~hintonr
|
|
Message is in Reply To:
 | | Wireless communication with the Handyboard
|
| Hello, I've been very busy trying to communicate with the Handyboard via a wireless link ( HP Development kit form Linx Technologies). I have run into a slight problem- The kit comes with 2 "development boards" - each contains a transmitter, (...) (25 years ago, 16-Apr-99, to lugnet.robotics.handyboard)
|
3 Messages in This Thread:
 
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
