Beginner, How to connect the second serial port?
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As above subject, how to connect the second serial port? Now i am
using BS 2p 24 pin and need to connect the second serial port to the
device.
using BS 2p 24 pin and need to connect the second serial port to the
device.
Comments
The big factor is do you need "true" RS232 levels or not.
If you are communicating over a short distance to another TTL-level
device, you can just connect the Stamp to the device. If the device has
real RS232 (with plus and minus voltages) you may be able to connect the
Stamp's output directly to the device and the Stamp's input through a
22K resistor to the device's output. This is not "correct RS232" but it
works in many, many cases. Many popular RS232 Ics will accept 0 and 5V
input even though it is not "to spec". The input protection diodes will
limit the pin voltage to 5.7 and -0.7V and the resistor will limit the
current. You can find this explained in the manual under SERIN and/or
SEROUT.
However, some devices won't accept 0/5V, or you may want the protection
and robustness of a real RS232 driver/receiver (real RS232 devices are
current limited and relatively noise immune, for example). In that case,
you probably will want a MAX232 chip. You can get these on a nice PC
board all ready to go at http://www.al-williams.com/awce/rs1.htm or just
the chips nearly anywhere (including
http://www.al-williams.com/awce/components.htm). This chip and four
capacitors allow you to do "true" RS232 with a single 0 and 5V supply.
Hope that helps!
Al Williams
AWC
* Floating point math for the Stamp, PIC, SX, or any microcontroller
http://www.al-williams.com/awce/pak1.htm
>
Original Message
> From: wanyia [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=DQUIogz0brADxG1o02FMgoQopm8uk368heMOp6-RPZq3MWafVVmWVtpU2CMuLJVhOBFmiSMAZmLL]wanyia@y...[/url
> Sent: Wednesday, April 17, 2002 3:37 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Beginner, How to connect the second
> serial port?
>
>
> As above subject, how to connect the second serial port? Now i am
> using BS 2p 24 pin and need to connect the second serial port to the
> device.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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>
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> http://docs.yahoo.com/info/terms/
>
--- In basicstamps@y..., "Al Williams" <alw@a...> wrote:
> Any two pins on the BS2P can become a serial port.
>
> The big factor is do you need "true" RS232 levels or not.
>
> If you are communicating over a short distance to another TTL-level
> device, you can just connect the Stamp to the device. If the device has
> real RS232 (with plus and minus voltages) you may be able to
connect the
> Stamp's output directly to the device and the Stamp's input through a
> 22K resistor to the device's output. This is not "correct RS232" but it
> works in many, many cases. Many popular RS232 Ics will accept 0
and 5V
> input even though it is not "to spec". The input protection diodes will
> limit the pin voltage to 5.7 and -0.7V and the resistor will limit the
> current. You can find this explained in the manual under SERIN and/or
> SEROUT.
>
> However, some devices won't accept 0/5V, or you may want the
protection
> and robustness of a real RS232 driver/receiver (real RS232 devices
are
> current limited and relatively noise immune, for example). In that
case,
> you probably will want a MAX232 chip. You can get these on a nice PC
> board all ready to go at http://www.al-williams.com/awce/rs1.htm or
just
> the chips nearly anywhere (including
> http://www.al-williams.com/awce/components.htm). This chip and
four
> capacitors allow you to do "true" RS232 with a single 0 and 5V supply.
>
> Hope that helps!
>
> Al Williams
> AWC
> * Floating point math for the Stamp, PIC, SX, or any microcontroller
> http://www.al-williams.com/awce/pak1.htm
>
>
>
> >
Original Message
> > From: wanyia [noparse][[/noparse]mailto:wanyia@y...]
> > Sent: Wednesday, April 17, 2002 3:37 AM
> > To: basicstamps@y...
> > Subject: [noparse][[/noparse]basicstamps] Beginner, How to connect the second
> > serial port?
> >
> >
> > As above subject, how to connect the second serial port? Now i am
> > using BS 2p 24 pin and need to connect the second serial port to
the
> > device.
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@y...
> > from the same email address that you subscribed. Text in the
> > Subject and Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> >