Subject:
|
Re: Connecting two HandyBoards through their serial ports
|
Newsgroups:
|
lugnet.robotics.handyboard
|
Date:
|
Thu, 12 Nov 1998 16:22:02 GMT
|
Original-From:
|
Fred G. Martin <fredm@media.mit.#IHateSpam#edu>
|
Viewed:
|
2236 times
|
| |
| |
Gads Bill, you are right and my info in the FAQ is dead wrong. I
have updated the FAQ with the corrected information.
*Thanks a lot* for working this one through. There are few things
more annoying than completely wrong documentation (compiler bugs maybe
are one of them).
Fred
In your message you said:
> Hello, everyone:
>
> Richard Drushel helped me solve the problem that I was having
> in getting two HandyBoards to communicate through their serial
> ports by suggesting that I check to be sure that the wiring on the
> RJ11 cable I was using corresponded to a "null modem" connection.
> Indeed, the connecting RJ11 cable I was using turned out NOT to be
> a null modem cable.
>
> On the HandyBoard FAQ, the following question tells how to
> connect two HandyBoards:
>
> > I want to plug two Handy Boards together so that they can
> > communicate. What kind of cable should I use?
> >
> > For this application, you must use the network style RJ11 cable
> > (as described above). Do not use the normal telephone style
> > RJ11 cable used to connect the HB to the serial interface, or
> > you will suffer the smoke and burn consequences noted above.
>
> The question before this one in the FAQ -- "The R11 on my
> Interface/Charger is smoking hot and is turning black! ..." --
> describes a network-style RJ11 cable by saying that if you hold
> the the ends of the cable plug-to-plug, both contact side up, the
> wires line up as follows:
>
> -------+ +--------
> --------- black| |yellow -----------
> --------- red| |green -----------
> --------- green| |redn -----------
> --------- yellow| |black -----------
> -------+ +--------
>
> Wiring an RJ11 cable this way avoids smoking the power supplies
> on the two HandyBoards, because the unswitched power leads of the
> two HandyBoards are connected, the ground leads are connected, the
> RxD leads are connected and the TxD leads are connected.
>
> Either the above diagram is wrong (I think that it's right,
> actually) or the advice in the FAQ to use this kind of cable is
> wrong, because it is necessary for the RxD and TxD leads on the
> two HandyBoards to be swapped and the ground leads to be matched.
> The unswitched power leads aren't needed for serial communication,
> but if they are connected, then they have to be matched. Namely, if
> you wire your RJ11 cable so that when you compare the cable plugs
> contact side up you get the pairings:
>
> -------+ +--------
> -------- black| |black ------------
> -------- red| |green ------------
> -------- green| |red ------------
> -------- yellow| |yellow ------------
> -------+ +--------
>
> This wiring switches TxD and RxD, but matches up the unswitched power
> leads and the ground leads on the two robots.
>
> When you use an RJ11 cable wired this way to connect two HandyBoards,
> then the serialio.c functions implement serial communication between
> the two HandyBoards quite nicely.
>
> Bill Bynum
>
|
|
Message is in Reply To:
2 Messages in This Thread:
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|