TWS Interface
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Posts: 46,084
I want to communicate with a Stamp from my PC keyboard via an RF link.
I need software that will let me send keystrokes directly to the serial port.
I need to know how to connect an interface IC - the Max232 - between the
serial port and the TWS input. The interface will be used for Transmit only.
Thanks
Sid
I need software that will let me send keystrokes directly to the serial port.
I need to know how to connect an interface IC - the Max232 - between the
serial port and the TWS input. The interface will be used for Transmit only.
Thanks
Sid
Comments
Paul
Original Message
From: <Newzed@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, March 26, 2001 4:20 PM
Subject: [noparse][[/noparse]basicstamps] TWS Interface
> I want to communicate with a Stamp from my PC keyboard via an RF link.
>
> I need software that will let me send keystrokes directly to the serial
port.
>
> I need to know how to connect an interface IC - the Max232 - between the
> serial port and the TWS input. The interface will be used for Transmit
only.
>
> Thanks
> Sid
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
Sid
working on a project for school involving RF communication between a PC and
a BOEBot. It's coming along fairly well. I am using Visual Basic on the
PC. Anyway, I did some research on RF and decided to use the TWS/RWS from
Reynolds, and am also using a MAX233 as an intermediary between the RS-232
serial cable and the transmitter.
Good luck to everyone on all of their projects!
Paul Contino
Original Message
From: <Newzed@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, March 26, 2001 7:26 PM
Subject: Re: [noparse][[/noparse]basicstamps] TWS Interface
> Which one, Paul. there are four different kinds.
>
> Sid
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
is a little more expensive, but allows for a bit faster data transfer rate
(200 kbps vs. 120 kbps) and a higher slew rate (something to do with speed
of op-amp voltage change, all internal to the MAX IC). The "C" is for
commercial use (temperature range, which I think 0-70 degrees Celsius should
work just fine for most applications). The "PP" is for PDIP (Plastic
Dual-In-Line). I know that there is a "WIDE SO" version, but I am not sure
exactly what that means -- some of the pin outs are for a different use.
Hope this helps. That's all that I can tell you. Everything is on the
Maxim website [noparse][[/noparse] www.maxim-ic.com ]. Do a search for MAX233 and take a look
at the data sheet (PDF).
Good luck.
Paul
Original Message
From: <Newzed@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, March 26, 2001 7:26 PM
Subject: Re: [noparse][[/noparse]basicstamps] TWS Interface
> Which one, Paul. there are four different kinds.
>
> Sid
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
First thing first: why don't you guys use the DS275 from Dallas
instead of the MAX232 or MAX233? Much easier to use in my view!
Second, is there any way to send data with a BS2 at the transmitting
end to the receiver hooked to a DS275(max232) at the receiving end
have the stamp debug screen read the incoming info? If not, how do I
get hyperterminal to read the incoming info...or a QBasic routine?
Thanks,
Corey.
--- In basicstamps@y..., "Paul Contino" <continpf@e...> wrote:
> My bad. Which MAX233 do you ask? I chose the MAX233ACPP. The "A"
version
> is a little more expensive, but allows for a bit faster data
transfer rate
> (200 kbps vs. 120 kbps) and a higher slew rate (something to do with
speed
> of op-amp voltage change, all internal to the MAX IC). The "C" is for
> commercial use (temperature range, which I think 0-70 degrees
Celsius should
> work just fine for most applications). The "PP" is for PDIP (Plastic
> Dual-In-Line). I know that there is a "WIDE SO" version, but I am
not sure
> exactly what that means -- some of the pin outs are for a different use.
> Hope this helps. That's all that I can tell you. Everything is on the
> Maxim website [noparse][[/noparse] www.maxim-ic.com ]. Do a search for MAX233 and take
a look
> at the data sheet (PDF).
>
> Good luck.
>
> Paul
>
>
>
>
>
Original Message
> From: <Newzed@a...>
> To: <basicstamps@y...>
> Sent: Monday, March 26, 2001 7:26 PM
> Subject: Re: [noparse][[/noparse]basicstamps] TWS Interface
>
>
> > Which one, Paul. there are four different kinds.
> >
> > Sid
> >
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
Why do I need a line driver/receiver? From what I can tell, many serial
ports will accept TTL levels as data in, and the Stamp manual itself has
an example of using a 22K resistor for data from a serial port to the
stamp. So, is it only when I must drive higer voltages from the stamp,
like for a serial port that won't accept TTL, or for greater cable
lengths? And why would a line receiver be better than a 22K resistor?
Anyone? I'm fairly hardware clueless.
Second, For the receiving end, I just hooked the data out of the RWS-434
directly to the input pin (pin 2 on a DB9) on the serial port and
connected the ground. Configured HyperTerminal for 2400b, 8N1. Just
worked.
Kevin
the_coin_guy@y... wrote:
>
> Hi all,
>
> First thing first: why don't you guys use the DS275 from Dallas
> instead of the MAX232 or MAX233? Much easier to use in my view!
>
> Second, is there any way to send data with a BS2 at the transmitting
> end to the receiver hooked to a DS275(max232) at the receiving end
> have the stamp debug screen read the incoming info? If not, how do I
> get hyperterminal to read the incoming info...or a QBasic routine?
>
> Thanks,
> Corey.
>
> --- In basicstamps@y..., "Paul Contino" <continpf@e...> wrote:
> > My bad. Which MAX233 do you ask? I chose the MAX233ACPP. The "A"
> version
> > is a little more expensive, but allows for a bit faster data
> transfer rate
> > (200 kbps vs. 120 kbps) and a higher slew rate (something to do with
> speed
> > of op-amp voltage change, all internal to the MAX IC). The "C" is for
> > commercial use (temperature range, which I think 0-70 degrees
> Celsius should
> > work just fine for most applications). The "PP" is for PDIP (Plastic
> > Dual-In-Line). I know that there is a "WIDE SO" version, but I am
> not sure
> > exactly what that means -- some of the pin outs are for a different use.
> > Hope this helps. That's all that I can tell you. Everything is on the
> > Maxim website [noparse][[/noparse] www.maxim-ic.com ]. Do a search for MAX233 and take
> a look
> > at the data sheet (PDF).
> >
> > Good luck.
> >
> > Paul
> >
> >
> >
> >
> >
Original Message
> > From: <Newzed@a...>
> > To: <basicstamps@y...>
> > Sent: Monday, March 26, 2001 7:26 PM
> > Subject: Re: [noparse][[/noparse]basicstamps] TWS Interface
> >
> >
> > > Which one, Paul. there are four different kinds.
> > >
> > > Sid
> > >
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> > >
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
level you should not.
FYI -- we used Max232's on some equipment where we used to work and got
500'+ distance at 300 baud. the new stuff used Max495's and we were able to
go 1500'+ at 9600 baud.
Original Message
> OK, I'll take a shot at the second if you can answer my other question.
> Why do I need a line driver/receiver? From what I can tell, many serial
> ports will accept TTL levels as data in, and the Stamp manual itself has
> an example of using a 22K resistor for data from a serial port to the
> stamp. So, is it only when I must drive higer voltages from the stamp,
> like for a serial port that won't accept TTL, or for greater cable
> lengths? And why would a line receiver be better than a 22K resistor?
> Anyone? I'm fairly hardware clueless.
>
> Second, For the receiving end, I just hooked the data out of the RWS-434
> directly to the input pin (pin 2 on a DB9) on the serial port and
> connected the ground. Configured HyperTerminal for 2400b, 8N1. Just
> worked.
>
> If you need true PC variety RS232, you have to use a line driver. For TTL
> level you should not.
I guess this is where my confusion is, the definition of 'true PC
variety RS232'. I've tried on 4 different PC, all where able to
directly read from the stamp, no line driver (all at short, < 4' cable
lengths). And assuming a short cable run is fine for a given
applicaiton so direct stamp->PC sems to work, what about PC->stamp. Do
you know of any badness from using the PC->22Kresistor->stamp method?
>
> FYI -- we used Max232's on some equipment where we used to work and got
> 500'+ distance at 300 baud. the new stuff used Max495's and we were able to
> go 1500'+ at 9600 baud.
OK, this sounds like a good example of greater cable length needing
higher voltages.
Thanks,
Kevin
that I also have had great results with the DS275.
= Steve
At 10:54 PM 03/27/2001 -0500, you wrote:
>Rodent wrote:
>>
>> If you need true PC variety RS232, you have to use a line driver. For TTL
>> level you should not.
>
>I guess this is where my confusion is, the definition of 'true PC
>variety RS232'. I've tried on 4 different PC, all where able to
>directly read from the stamp, no line driver (all at short, < 4' cable
>lengths). And assuming a short cable run is fine for a given
>applicaiton so direct stamp->PC sems to work, what about PC->stamp. Do
>you know of any badness from using the PC->22Kresistor->stamp method?
>
>>
>> FYI -- we used Max232's on some equipment where we used to work and got
>> 500'+ distance at 300 baud. the new stuff used Max495's and we were able to
>> go 1500'+ at 9600 baud.
>
>OK, this sounds like a good example of greater cable length needing
>higher voltages.
>
>Thanks,
>
>Kevin
>
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
You might wind up toasting your stamp if you connect one of the regular data
ports to a PC serial port.
If you look at a schematic for the BS2 processors, you'll see the serial
port for the PC has a simple line driver built out of a few transistors.
Original Message
> > If you need true PC variety RS232, you have to use a line driver. For
TTL
> > level you should not.
>
> I guess this is where my confusion is, the definition of 'true PC
> variety RS232'. I've tried on 4 different PC, all where able to
> directly read from the stamp, no line driver (all at short, < 4' cable
> lengths). And assuming a short cable run is fine for a given
> applicaiton so direct stamp->PC sems to work, what about PC->stamp. Do
> you know of any badness from using the PC->22Kresistor->stamp method?
line driver at all.
Original Message
> I've not been following this thread too closely, but would like to throw
in
> that I also have had great results with the DS275.
from the serial port, hence the 22k resistor (I imagine). Writing to
the serial port seems like it'd only work of the serial port was able to
accept the non-standard RS-232 voltages.
Still just wondering if I'm missing something here. Why does everyone
seem to jump to the added cost/component of a line driver?
Is this just a case of, "just because it works for me, in my situation,
doesn't mean it'll work for everyone, so always best to follow the
spec"?
ko
Rodent wrote:
>
> If I remember right, true RS232 is + / - 12 volts, where TTL is 0-5 volts.
> You might wind up toasting your stamp if you connect one of the regular data
> ports to a PC serial port.
>
> If you look at a schematic for the BS2 processors, you'll see the serial
> port for the PC has a simple line driver built out of a few transistors.
>
>
Original Message
>
> > > If you need true PC variety RS232, you have to use a line driver. For
> TTL
> > > level you should not.
> >
> > I guess this is where my confusion is, the definition of 'true PC
> > variety RS232'. I've tried on 4 different PC, all where able to
> > directly read from the stamp, no line driver (all at short, < 4' cable
> > lengths). And assuming a short cable run is fine for a given
> > applicaiton so direct stamp->PC sems to work, what about PC->stamp. Do
> > you know of any badness from using the PC->22Kresistor->stamp method?
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
in fact I just finished a project this evening that uses the 22K resistor
to protect the pic's( or stamp) internal protection diodes from blowing
apart. Any time you put a voltage greater then about 0.7 vdc above the
stamps supply voltage, typically 5 vdc,the internal diodes will begin to
conduct. This allows happens if you put a voltage less than -0.7 vdc below
ground.
The stamps internal protection diodes are rated for a maximum of 20
milliamps. I've run over 25 milliamps through the protection diodes for
several days to see if they would fail, and they did not.
So, If you put + 12 vdc on to your stamp pin through a 22 K resistor, then
the current would be about 12 vdc-5.7vdc= 6.3 vdc/22 K = 0.286 milliamps
through the protection diode, well within it's range and it should work
just fine.
It's also a good idea to use a resistor on your output pin, something
around 1 K to protect it from accidental shorts.
Most if not all pc's, included laptops should have no trouble recognizing
the stamp's output pin swing of 0 to +5 vdc.....
At 10:04 PM 03/27/2001 -0600, you wrote:
>We're not trying to dis the DS275, just trying to justify the need for any
>line driver at all.
>
>
Original Message
>
>
>> I've not been following this thread too closely, but would like to throw
>in
>> that I also have had great results with the DS275.
>
>
>
>
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>Still just wondering if I'm missing something here. Why does everyone
>seem to jump to the added cost/component of a line driver?
For me the reason is reliability, I build projects for other people and
would hate to see a unit returned due to the loss of a protection diode.
Thanks to the PIC's robust I/O protection diodes, you can get away with it
most of the time..............Then again a line driver for $2 or $3 keeps
the pic happy.
fwiw
Steve
Kein
sargent@s... wrote:
>
> >
> >Still just wondering if I'm missing something here. Why does everyone
> >seem to jump to the added cost/component of a line driver?
>
> For me the reason is reliability, I build projects for other people and
> would hate to see a unit returned due to the loss of a protection diode.
> Thanks to the PIC's robust I/O protection diodes, you can get away with it
> most of the time..............Then again a line driver for $2 or $3 keeps
> the pic happy.
>
> fwiw
>
> Steve
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
the current revision) to define standards for interconnection of data
transmission equipment ("DTE", e.g. a computer) and data
communications equipment ("DCE", usually a modem). At the time DB-25
connectors were specified, a large number of wires were defined in the
cable (many optional) and many electrical requirements are specified.
The objective was to guarantee that if ports and cables met the
standard they could be safely interconnected and expected to work. The
following site, among many others,
http://www.rad.com/networks/1995/rs232/rs232.htm will tell yhou a lot
about the actual standard.
The computer industry later abandoned DB-25 in favor of the smaller
DB-9 connectors. This still allows enough connections to support
external modems but I don't think the RS-232 standard has actually
been modified to include this subset. The standard also requires the
signal sources to be between +3 and +12 when positive and -3 and -12
when negative. Receivers are supposed to tolerate up to +25 to -25
volts. But most, if not all, computers have been designed to accept
"TTL" signal inputs as well as "real" RS-232. TTL signals must be
relatively "clean" to work well.
Stamp pins do not meet the port requirements for RS-232 but driver
chips such as the MAX232 do. The driver chips are also compatible with
Stamp pins. Voila! A $3 interface that meets standards in both
directions and protects your Stamp. There are other workarounds, such
as adding resistors here and there, that will work in specific cases
but I wouldn't trust this for all situations without knowing the
details. The drivers are also increasingly useful for any combinations
of higher data rates and longer cables.
Cable capacitance causes signal distortion that increases with the
length of the cable. This typically (depending on the driver, the
receiver and the cable selected) supports RS-232 9600 baud
communications over at least 100 cable feet. Halve the distance every
time the rate is doubled or vice versa. However, the RS-232 standard
actually specifies cables only to a maximum of 50 feet. Your mileage
may vary.
I hope this backgound stuff helps.
--- In basicstamps@y..., Kevin Olalde <kolalde@h...> wrote:
> Yep, I'd certainly be worried about nuking the stamp trying to
_read_
> from the serial port, hence the 22k resistor (I imagine). Writing
to
> the serial port seems like it'd only work of the serial port was
able to
> accept the non-standard RS-232 voltages.
>
> Still just wondering if I'm missing something here. Why does
everyone
> seem to jump to the added cost/component of a line driver?
>
> Is this just a case of, "just because it works for me, in my
situation,
> doesn't mean it'll work for everyone, so always best to follow the
> spec"?
>
> ko
>
> Rodent wrote:
> >
> > If I remember right, true RS232 is + / - 12 volts, where TTL is
0-5 volts.
> > You might wind up toasting your stamp if you connect one of the
regular data
> > ports to a PC serial port.
> >
> > If you look at a schematic for the BS2 processors, you'll see the
serial
> > port for the PC has a simple line driver built out of a few
transistors.
> >
> >
Original Message
> >
> > > > If you need true PC variety RS232, you have to use a line
driver. For
> > TTL
> > > > level you should not.
> > >
> > > I guess this is where my confusion is, the definition of 'true
PC
> > > variety RS232'. I've tried on 4 different PC, all where able to
> > > directly read from the stamp, no line driver (all at short, < 4'
cable
> > > lengths). And assuming a short cable run is fine for a given
> > > applicaiton so direct stamp->PC sems to work, what about
PC->stamp. Do
> > > you know of any badness from using the PC->22Kresistor->stamp
method?
> >
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
computers today? (if there is such a place)
Robert Staph, W3RCS
The Center for Advanced Technologies
Original Message
From: <fdavidson@m...>
To: <basicstamps@yahoogroups.com>
Sent: Wednesday, March 28, 2001 9:15 AM
Subject: [noparse][[/noparse]basicstamps] Re: TWS Interface
> The RS-232 Standard was developed many years ago (RS-232C is, I think,
> the current revision) to define standards for interconnection of data
> transmission equipment ("DTE", e.g. a computer) and data
> communications equipment ("DCE", usually a modem). At the time DB-25
> connectors were specified, a large number of wires were defined in the
> cable (many optional) and many electrical requirements are specified.
> The objective was to guarantee that if ports and cables met the
> standard they could be safely interconnected and expected to work. The
> following site, among many others,
> http://www.rad.com/networks/1995/rs232/rs232.htm will tell yhou a lot
> about the actual standard.
>
> The computer industry later abandoned DB-25 in favor of the smaller
> DB-9 connectors. This still allows enough connections to support
> external modems but I don't think the RS-232 standard has actually
> been modified to include this subset. The standard also requires the
> signal sources to be between +3 and +12 when positive and -3 and -12
> when negative. Receivers are supposed to tolerate up to +25 to -25
> volts. But most, if not all, computers have been designed to accept
> "TTL" signal inputs as well as "real" RS-232. TTL signals must be
> relatively "clean" to work well.
>
> Stamp pins do not meet the port requirements for RS-232 but driver
> chips such as the MAX232 do. The driver chips are also compatible with
> Stamp pins. Voila! A $3 interface that meets standards in both
> directions and protects your Stamp. There are other workarounds, such
> as adding resistors here and there, that will work in specific cases
> but I wouldn't trust this for all situations without knowing the
> details. The drivers are also increasingly useful for any combinations
> of higher data rates and longer cables.
>
> Cable capacitance causes signal distortion that increases with the
> length of the cable. This typically (depending on the driver, the
> receiver and the cable selected) supports RS-232 9600 baud
> communications over at least 100 cable feet. Halve the distance every
> time the rate is doubled or vice versa. However, the RS-232 standard
> actually specifies cables only to a maximum of 50 feet. Your mileage
> may vary.
>
> I hope this backgound stuff helps.
>
>
> --- In basicstamps@y..., Kevin Olalde <kolalde@h...> wrote:
> > Yep, I'd certainly be worried about nuking the stamp trying to
> _read_
> > from the serial port, hence the 22k resistor (I imagine). Writing
> to
> > the serial port seems like it'd only work of the serial port was
> able to
> > accept the non-standard RS-232 voltages.
> >
> > Still just wondering if I'm missing something here. Why does
> everyone
> > seem to jump to the added cost/component of a line driver?
> >
> > Is this just a case of, "just because it works for me, in my
> situation,
> > doesn't mean it'll work for everyone, so always best to follow the
> > spec"?
> >
> > ko
> >
> > Rodent wrote:
> > >
> > > If I remember right, true RS232 is + / - 12 volts, where TTL is
> 0-5 volts.
> > > You might wind up toasting your stamp if you connect one of the
> regular data
> > > ports to a PC serial port.
> > >
> > > If you look at a schematic for the BS2 processors, you'll see the
> serial
> > > port for the PC has a simple line driver built out of a few
> transistors.
> > >
> > >
Original Message
> > >
> > > > > If you need true PC variety RS232, you have to use a line
> driver. For
> > > TTL
> > > > > level you should not.
> > > >
> > > > I guess this is where my confusion is, the definition of 'true
> PC
> > > > variety RS232'. I've tried on 4 different PC, all where able to
> > > > directly read from the stamp, no line driver (all at short, < 4'
> cable
> > > > lengths). And assuming a short cable run is fine for a given
> > > > applicaiton so direct stamp->PC sems to work, what about
> PC->stamp. Do
> > > > you know of any badness from using the PC->22Kresistor->stamp
> method?
> > >
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
So I finished my cup of coffee, and then I said "Why go through all of this
TWS/Max232/22K resistor stuff?"
Pin 3 of the Stamp DB9 connector - the Tx pin - goes directly to the serin
pin on the Stamp module, which is really pin 16.
So at the very beginning of the Train program I wrote:
N9600 con 16468
com var byte
serin 16, N9600, [noparse][[/noparse]com]
if com = "A" then start1
if com = "B" then stop1 'and so on for a few more "if's"
Loaded the program into Stamp, exited the Stamp Editor to free up Com1 port,
the went to Hyperterminal. Hit A on the keyboard and Train 1 started up and
ran. Hit B on the keyboard and Train 1 stopped.
All so very simple once I had Hyperterminal - no wires, no TWS, no line
driver, I didn't even have to move the serial cable.
I can now make the train do anything I want it to just by hitting the right
letter on the keyboard.
Sid
I find www.google.com very good at looking up these kinds of things.
That's what I used to find RS-232 documents. Google should be very
effective if you know the name of the standard or at least an acronym
that is related.
But I can't help you with a centralized source for computer standards
in general.
Fred, K1IZM
--- In basicstamps@y..., "Robert Staph" <rstaph@a...> wrote:
> Can you point me to a web page that has alot of the standards used
in
> computers today? (if there is such a place)
>
> Robert Staph, W3RCS
> The Center for Advanced Technologies
>
>
>
Original Message
> From: <fdavidson@m...>
> To: <basicstamps@y...>
> Sent: Wednesday, March 28, 2001 9:15 AM
> Subject: [noparse][[/noparse]basicstamps] Re: TWS Interface
>
>
> > The RS-232 Standard was developed many years ago (RS-232C is, I
think,
> > the current revision) to define standards for interconnection of
data
> > transmission equipment ("DTE", e.g. a computer) and data
> > communications equipment ("DCE", usually a modem). At the time
DB-25
> > connectors were specified, a large number of wires were defined in
the
> > cable (many optional) and many electrical requirements are
specified.
> > The objective was to guarantee that if ports and cables met the
> > standard they could be safely interconnected and expected to work.
The
> > following site, among many others,
> > http://www.rad.com/networks/1995/rs232/rs232.htm will tell yhou a
lot
> > about the actual standard.
> >
> > The computer industry later abandoned DB-25 in favor of the
smaller
> > DB-9 connectors. This still allows enough connections to support
> > external modems but I don't think the RS-232 standard has actually
> > been modified to include this subset. The standard also requires
the
> > signal sources to be between +3 and +12 when positive and -3 and
-12
> > when negative. Receivers are supposed to tolerate up to +25 to -25
> > volts. But most, if not all, computers have been designed to
accept
> > "TTL" signal inputs as well as "real" RS-232. TTL signals must be
> > relatively "clean" to work well.
> >
> > Stamp pins do not meet the port requirements for RS-232 but driver
> > chips such as the MAX232 do. The driver chips are also compatible
with
> > Stamp pins. Voila! A $3 interface that meets standards in both
> > directions and protects your Stamp. There are other workarounds,
such
> > as adding resistors here and there, that will work in specific
cases
> > but I wouldn't trust this for all situations without knowing the
> > details. The drivers are also increasingly useful for any
combinations
> > of higher data rates and longer cables.
> >
> > Cable capacitance causes signal distortion that increases with the
> > length of the cable. This typically (depending on the driver, the
> > receiver and the cable selected) supports RS-232 9600 baud
> > communications over at least 100 cable feet. Halve the distance
every
> > time the rate is doubled or vice versa. However, the RS-232
standard
> > actually specifies cables only to a maximum of 50 feet. Your
mileage
> > may vary.
> >
> > I hope this backgound stuff helps.
> >
> >
> > --- In basicstamps@y..., Kevin Olalde <kolalde@h...> wrote:
> > > Yep, I'd certainly be worried about nuking the stamp trying to
> > _read_
> > > from the serial port, hence the 22k resistor (I imagine).
Writing
> > to
> > > the serial port seems like it'd only work of the serial port was
> > able to
> > > accept the non-standard RS-232 voltages.
> > >
> > > Still just wondering if I'm missing something here. Why does
> > everyone
> > > seem to jump to the added cost/component of a line driver?
> > >
> > > Is this just a case of, "just because it works for me, in my
> > situation,
> > > doesn't mean it'll work for everyone, so always best to follow
the
> > > spec"?
> > >
> > > ko
> > >
> > > Rodent wrote:
> > > >
> > > > If I remember right, true RS232 is + / - 12 volts, where TTL
is
> > 0-5 volts.
> > > > You might wind up toasting your stamp if you connect one of
the
> > regular data
> > > > ports to a PC serial port.
> > > >
> > > > If you look at a schematic for the BS2 processors, you'll see
the
> > serial
> > > > port for the PC has a simple line driver built out of a few
> > transistors.
> > > >
> > > >
Original Message
> > > >
> > > > > > If you need true PC variety RS232, you have to use a line
> > driver. For
> > > > TTL
> > > > > > level you should not.
> > > > >
> > > > > I guess this is where my confusion is, the definition of
'true
> > PC
> > > > > variety RS232'. I've tried on 4 different PC, all where
able to
> > > > > directly read from the stamp, no line driver (all at short,
< 4'
> > cable
> > > > > lengths). And assuming a short cable run is fine for a
given
> > > > > applicaiton so direct stamp->PC sems to work, what about
> > PC->stamp. Do
> > > > > you know of any badness from using the
PC->22Kresistor->stamp
> > method?
> > > >
> > > >
> > > >
> > > > Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> >
> >
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
> >
> >