Stamp <-> PC via Parallax RF transceivers

Archiver

Hi,

I'm working on a final year project which involves wireless control
of a Growbot (Stamp controlled robot), via a PC. I've purchased a
pair of Parallax's RF transceivers (#27994). I'm using a MAX232 chip
to convert to/from RS232 <-> TTL on the PC end.

I've been able to successfully transmit byes from the PC to the Stamp
(with the Stamps's TX pin disconnected), and from the Stamp to the PC
(with the PC's TX pin disconnected). However, with both TX pins
connected I'm unable to receive byes; I think this stems from the
fact that the serial communication "idles" at logic high, and
interferes with the other transmitting signal. Could this be the
case?

If so, I'm thinking about physically inverting the signals between
the MAX232 and the transceiver (on the PC end) and using the Stamp's
serin and serout inverting options (on the Stamp end). This would
invert all signals to/from both transceivers and cause the
transmitters to "idle" at logic low.

I'd appreciate any thoughts on the issue. Thanks.

Marcus

Archiver

Hey

What you're doing sounds exactly what I did a few months ago. We're
building two vehicles, that can transmit/receive data from a computer
station.

But, that's exactly what I did. I put an inverter on both ends.
Works fine. The TX pin on the PC end is always high, and I couldn't
find any other option than to invert the sucker.

By the way, what are you programming in on the PC side? That's the
stage I'm at now. I 'borrowed' some code from beyondlogic.org to get
the serial port working, but, I'm wondering if there is an easier way
or not...

Anyways..hope to hear from u soon

Debu

--- In basicstamps@y..., "freud_20" <8mjjw@q...> wrote:
> Hi,
>
> I'm working on a final year project which involves wireless control
> of a Growbot (Stamp controlled robot), via a PC. I've purchased a
> pair of Parallax's RF transceivers (#27994). I'm using a MAX232
chip
> to convert to/from RS232 <-> TTL on the PC end.
>
> I've been able to successfully transmit byes from the PC to the
Stamp
> (with the Stamps's TX pin disconnected), and from the Stamp to the
PC
> (with the PC's TX pin disconnected). However, with both TX pins
> connected I'm unable to receive byes; I think this stems from the
> fact that the serial communication "idles" at logic high, and
> interferes with the other transmitting signal. Could this be the
> case?
>
> If so, I'm thinking about physically inverting the signals between
> the MAX232 and the transceiver (on the PC end) and using the
Stamp's
> serin and serout inverting options (on the Stamp end). This would
> invert all signals to/from both transceivers and cause the
> transmitters to "idle" at logic low.
>
> I'd appreciate any thoughts on the issue. Thanks.
>
> Marcus

Archiver

Hey

What you're doing sounds exactly what I did a few months ago. We're
building two vehicles, that can transmit/receive data from a computer
station.

But, that's exactly what I did. I put an inverter on both ends.
Works fine. The TX pin on the PC end is always high, and I couldn't
find any other option than to invert the sucker.

By the way, what are you programming in on the PC side? That's the
stage I'm at now. I 'borrowed' some code from beyondlogic.org to get
the serial port working, but, I'm wondering if there is an easier way
or not...

Anyways..hope to hear from u soon

Debu

--- In basicstamps@y..., "freud_20" <8mjjw@q...> wrote:
> Hi,
>
> I'm working on a final year project which involves wireless control
> of a Growbot (Stamp controlled robot), via a PC. I've purchased a
> pair of Parallax's RF transceivers (#27994). I'm using a MAX232
chip
> to convert to/from RS232 <-> TTL on the PC end.
>
> I've been able to successfully transmit byes from the PC to the
Stamp
> (with the Stamps's TX pin disconnected), and from the Stamp to the
PC
> (with the PC's TX pin disconnected). However, with both TX pins
> connected I'm unable to receive byes; I think this stems from the
> fact that the serial communication "idles" at logic high, and
> interferes with the other transmitting signal. Could this be the
> case?
>
> If so, I'm thinking about physically inverting the signals between
> the MAX232 and the transceiver (on the PC end) and using the
Stamp's
> serin and serout inverting options (on the Stamp end). This would
> invert all signals to/from both transceivers and cause the
> transmitters to "idle" at logic low.
>
> I'd appreciate any thoughts on the issue. Thanks.
>
> Marcus

Archiver

Debu,

Thanks - I will go ahead and try the inverter. As for programming
the PC serial port, I'm using an ActiveX Control, MSComm, which can
be used very easily from Visual Basic 6.0. It abstracts the serial
port's UART, so you don't have to fiddle with control registers at
all. I too looked into controlling the UART directly and was quite
releived to find the required functionality through VB, which I'm
also conveniently using for the project's GUI.

Let me know if you need further details.

Marcus

--- In basicstamps@y..., "debu_sen_22" <debu_sen_22@y...> wrote:
> Hey
>
> What you're doing sounds exactly what I did a few months ago.
We're
> building two vehicles, that can transmit/receive data from a
computer
> station.
>
> But, that's exactly what I did. I put an inverter on both ends.
> Works fine. The TX pin on the PC end is always high, and I
couldn't
> find any other option than to invert the sucker.
>
> By the way, what are you programming in on the PC side? That's the
> stage I'm at now. I 'borrowed' some code from beyondlogic.org to
get
> the serial port working, but, I'm wondering if there is an easier
way
> or not...
>
> Anyways..hope to hear from u soon
>
> Debu
>
> --- In basicstamps@y..., "freud_20" <8mjjw@q...> wrote:
> > Hi,
> >
> > I'm working on a final year project which involves wireless
control
> > of a Growbot (Stamp controlled robot), via a PC. I've purchased
a
> > pair of Parallax's RF transceivers (#27994). I'm using a MAX232
> chip
> > to convert to/from RS232 <-> TTL on the PC end.
> >
> > I've been able to successfully transmit byes from the PC to the
> Stamp
> > (with the Stamps's TX pin disconnected), and from the Stamp to
the
> PC
> > (with the PC's TX pin disconnected). However, with both TX pins
> > connected I'm unable to receive byes; I think this stems from the
> > fact that the serial communication "idles" at logic high, and
> > interferes with the other transmitting signal. Could this be the
> > case?
> >
> > If so, I'm thinking about physically inverting the signals
between
> > the MAX232 and the transceiver (on the PC end) and using the
> Stamp's
> > serin and serout inverting options (on the Stamp end). This
would
> > invert all signals to/from both transceivers and cause the
> > transmitters to "idle" at logic low.
> >
> > I'd appreciate any thoughts on the issue. Thanks.
> >
> > Marcus

Archiver

Hi there,

I am not using a stamp as my microcontroller but I purchased a pair
of the Parallax RF transceivers to some data tranmission for my
graduate project. I thought somebody could give me a few troubleshooting
points. I am able to wire up the modules and have them do the switch
mode operation i.e in1 turns on out1 which I assume that means the
RF works fine but the serial mode doesn't function properly.

My micro (a 8051 based) is connected to the serial pin of the module.
I have verified that this is running at 9600 because I can connect this
directly to my PC and have it spit out my numbers in hyperterm. So I
connect my micro through a max232 to do the level shifting then
to the serial pin on transceiver. I am not using the flow control rather
my micro is just spitting out a '1' every second which I thought is slow
enough of the transceiver.

On my receiver, I connect the receive data pin to another max232 and
then on to my PC on pin 3 on a DB9 and pin 5 on the DB9 is grounded.

With this setup nothing comes through. My mode pin on both modules
are both high to enable serial mode. Any ideas or clues? I've been really
stumped by this for 2 days since each part seems to work fine.

Much thanks in advance,
Thomas