5V TTL to true rs232
Archiver
Posts: 46,084
Hi Folks,
I'm trying to interface a Stamp to a serial device on TX and RX which is
*very* fussy about the rs232 voltages. I've tried Max232 to interface, but
the device remains silent. This seems to be becauseMax232 outputs a max of
+/- 8.5v unloaded and the device is loading it down to +/-8v which just
does not seem to be enough to wake up the device.
It works fine however on my PC, which works at +12 and - 12v. I know it is
not my code because I've done lots of subsitution testing to prove the
assertion on the 8v issue.
Does anyone know of a Max 232 type device which works to true 12v or higher?
I'm so desperate I'm willing to work with a +/- 12v PSU to get this working.
Any help would be appreciated.
Thanks
Tony Wells
I'm trying to interface a Stamp to a serial device on TX and RX which is
*very* fussy about the rs232 voltages. I've tried Max232 to interface, but
the device remains silent. This seems to be becauseMax232 outputs a max of
+/- 8.5v unloaded and the device is loading it down to +/-8v which just
does not seem to be enough to wake up the device.
It works fine however on my PC, which works at +12 and - 12v. I know it is
not my code because I've done lots of subsitution testing to prove the
assertion on the 8v issue.
Does anyone know of a Max 232 type device which works to true 12v or higher?
I'm so desperate I'm willing to work with a +/- 12v PSU to get this working.
Any help would be appreciated.
Thanks
Tony Wells
Comments
Sorry to hear the MAX232 isn't working. +/- 5V is supposed to do the
trick.
The "traditional" way to go is a 1488 and 1489. One is the line driver
and the other is the line receiver. You provide +/- 12V and you are in
business. Don't mess with the ajustment pins because with some vendors
they never worked correctly anyway. I don't know who still carries
these.
Are you absolutely certain the voltage is the problem? If you hook your
Stamp to the PC does it seem to do what you expect? Something else to
think about: if you are able to talk from the PC to the device through a
straight cable, and you can talk from the Stamp to the PC with a
straight cable, then you need a cross cable to talk between the Stamp
and the device (how's that for a syllogism?).
What is it that makes you certain it is a voltage-related issue?
Al Williams
AWC
* Floating point A/D
http://www.al-williams.com/awce/pak9.htm
>
Original Message
> From: tony.wells@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=3Ywr6LucOc0_PHX4m4Zly-yb5Quij5jyv6K1gduFK9rSa_MhOtNNoimy1U63Xx7ohq-8DrN26BatJZlDLw]tony.wells@a...[/url
> Sent: Monday, January 21, 2002 4:13 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
>
>
> Hi Folks,
>
> I'm trying to interface a Stamp to a serial device on TX and
> RX which is
> *very* fussy about the rs232 voltages. I've tried Max232 to
> interface, but the device remains silent. This seems to be
> becauseMax232 outputs a max of
> +/- 8.5v unloaded and the device is loading it down to +/-8v which
> +just
> does not seem to be enough to wake up the device.
>
> It works fine however on my PC, which works at +12 and - 12v.
> I know it is not my code because I've done lots of
> subsitution testing to prove the assertion on the 8v issue.
>
> Does anyone know of a Max 232 type device which works to true
> 12v or higher? I'm so desperate I'm willing to work with a
> +/- 12v PSU to get this working.
>
> Any help would be appreciated.
>
> Thanks
>
> Tony Wells
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> 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/
>
using a max232 chip they invert the data stream
Original Message
From: "Al Williams" <alw@a...>
To: <basicstamps@yahoogroups.com>
Sent: January 21, 2002 2:35 PM
Subject: RE: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
Hi Tony,
Sorry to hear the MAX232 isn't working. +/- 5V is supposed to do
the
trick.
The "traditional" way to go is a 1488 and 1489. One is the line
driver
and the other is the line receiver. You provide +/- 12V and you
are in
business. Don't mess with the ajustment pins because with some
vendors
they never worked correctly anyway. I don't know who still
carries
these.
Are you absolutely certain the voltage is the problem? If you
hook your
Stamp to the PC does it seem to do what you expect? Something
else to
think about: if you are able to talk from the PC to the device
through a
straight cable, and you can talk from the Stamp to the PC with a
straight cable, then you need a cross cable to talk between the
Stamp
and the device (how's that for a syllogism?).
What is it that makes you certain it is a voltage-related issue?
Al Williams
AWC
* Floating point A/D
http://www.al-williams.com/awce/pak9.htm
>
Original Message
> From: tony.wells@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=eCGPf2C95O3sf6eS3g0zPRZblgEUIPnGIQgB_b76PdS2RzK_Ztje7H6BS8rQdZ-9JgiwY1Pv_wW6pC3c65mJ2vc]tony.wells@a...[/url
> Sent: Monday, January 21, 2002 4:13 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
>
>
> Hi Folks,
>
> I'm trying to interface a Stamp to a serial device on TX and
> RX which is
> *very* fussy about the rs232 voltages. I've tried Max232 to
> interface, but the device remains silent. This seems to be
> becauseMax232 outputs a max of
> +/- 8.5v unloaded and the device is loading it down to +/-8v
which
> +just
> does not seem to be enough to wake up the device.
>
> It works fine however on my PC, which works at +12 and - 12v.
> I know it is not my code because I've done lots of
> subsitution testing to prove the assertion on the 8v issue.
>
> Does anyone know of a Max 232 type device which works to true
> 12v or higher? I'm so desperate I'm willing to work with a
> +/- 12v PSU to get this working.
>
> Any help would be appreciated.
>
> Thanks
>
> Tony Wells
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> 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/
>
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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/
> Are you absolutely certain the voltage is the problem? If you hook your
> Stamp to the PC does it seem to do what you expect? Something else to
> think about: if you are able to talk from the PC to the device through a
> straight cable, and you can talk from the Stamp to the PC with a
> straight cable, then you need a cross cable to talk between the Stamp
> and the device (how's that for a syllogism?).
>
> What is it that makes you certain it is a voltage-related issue?
>
I'm aware of the 1488 thanks, but was hoping there was a 5v powered chip
which outputs +/- 12v.
I'm absolutely sure it is voltage related because::
a. The external device (a Rugby MSF receiver) is normally powered from the
rs232 line and when I connected the device to the PC I identified the pin
supplying -12v from the PC which causes the device to wake up. When I simply
move the same wire from the PC end and move it across to the Stamp Max232
equivalent which supples -8v the device goes back to sleep and remains as
sleepy as Mr Sleepy in Sleepyville. When I move the wire back to the PC the
device wakes up and is as alert as Mr Rabbit in a field of angry farmers!
> Sorry to hear the MAX232 isn't working. +/- 5V is supposed to do the
> trick.
*Your* max232 is working fine - its was for another project which is done
and dusted....
Original Message
From: "Al Williams" <alw@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, January 21, 2002 10:35 PM
Subject: RE: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
> Hi Tony,
>
> Sorry to hear the MAX232 isn't working. +/- 5V is supposed to do the
> trick.
>
> The "traditional" way to go is a 1488 and 1489. One is the line driver
> and the other is the line receiver. You provide +/- 12V and you are in
> business. Don't mess with the ajustment pins because with some vendors
> they never worked correctly anyway. I don't know who still carries
> these.
>
> Are you absolutely certain the voltage is the problem? If you hook your
> Stamp to the PC does it seem to do what you expect? Something else to
> think about: if you are able to talk from the PC to the device through a
> straight cable, and you can talk from the Stamp to the PC with a
> straight cable, then you need a cross cable to talk between the Stamp
> and the device (how's that for a syllogism?).
>
> What is it that makes you certain it is a voltage-related issue?
>
> Al Williams
> AWC
> * Floating point A/D
> http://www.al-williams.com/awce/pak9.htm
>
>
>
> >
Original Message
> > From: tony.wells@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=Nu6GQ1dDKlVq5PdOqrKwpal-WIcmENA3XbLgDq3iNTN2srgoRaFJytebDmWbJ2FnP9Pq6MkC1tke48B7dg]tony.wells@a...[/url
> > Sent: Monday, January 21, 2002 4:13 PM
> > To: basicstamps@yahoogroups.com
> > Subject: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
> >
> >
> > Hi Folks,
> >
> > I'm trying to interface a Stamp to a serial device on TX and
> > RX which is
> > *very* fussy about the rs232 voltages. I've tried Max232 to
> > interface, but the device remains silent. This seems to be
> > becauseMax232 outputs a max of
> > +/- 8.5v unloaded and the device is loading it down to +/-8v which
> > +just
> > does not seem to be enough to wake up the device.
> >
> > It works fine however on my PC, which works at +12 and - 12v.
> > I know it is not my code because I've done lots of
> > subsitution testing to prove the assertion on the 8v issue.
> >
> > Does anyone know of a Max 232 type device which works to true
> > 12v or higher? I'm so desperate I'm willing to work with a
> > +/- 12v PSU to get this working.
> >
> > Any help would be appreciated.
> >
> > Thanks
> >
> > Tony Wells
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > 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/
> >
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> 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/
>
>
>
The max232 generates normally +/- 10V from a single 5V and requires four
0.1uF caps to do so.
It may be your device draws a little bit more current than usual hence
the -8V.
I regarly use 10uF caps without problems and these keep the voltages to +/-
10V.
With the increased caps you can draw more current without decreasing the
voltages too much.
Regards peter
Oorspronkelijk bericht
Van: tony.wells@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=UxKDjy5XEYxAUrhSzDpjRNi4-ZFWysOe-J17QQaEySSCzBwrKuSQ8OlUzF6VB7wgo_4CKF91R6aXdClhkXB2ZQ]tony.wells@a...[/url
Verzonden: maandag 21 januari 2002 20:25
Aan: basicstamps@yahoogroups.com
Onderwerp: Re: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
AW wrote:
> Are you absolutely certain the voltage is the problem? If you hook your
> Stamp to the PC does it seem to do what you expect? Something else to
> think about: if you are able to talk from the PC to the device through a
> straight cable, and you can talk from the Stamp to the PC with a
> straight cable, then you need a cross cable to talk between the Stamp
> and the device (how's that for a syllogism?).
>
> What is it that makes you certain it is a voltage-related issue?
>
I'm aware of the 1488 thanks, but was hoping there was a 5v powered chip
which outputs +/- 12v.
I'm absolutely sure it is voltage related because::
a. The external device (a Rugby MSF receiver) is normally powered from the
rs232 line and when I connected the device to the PC I identified the pin
supplying -12v from the PC which causes the device to wake up. When I simply
move the same wire from the PC end and move it across to the Stamp Max232
equivalent which supples -8v the device goes back to sleep and remains as
sleepy as Mr Sleepy in Sleepyville. When I move the wire back to the PC the
device wakes up and is as alert as Mr Rabbit in a field of angry farmers!
> Sorry to hear the MAX232 isn't working. +/- 5V is supposed to do the
> trick.
*Your* max232 is working fine - its was for another project which is done
and dusted....
Original Message
From: "Al Williams" <alw@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, January 21, 2002 10:35 PM
Subject: RE: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
> Hi Tony,
>
> Sorry to hear the MAX232 isn't working. +/- 5V is supposed to do the
> trick.
>
> The "traditional" way to go is a 1488 and 1489. One is the line driver
> and the other is the line receiver. You provide +/- 12V and you are in
> business. Don't mess with the ajustment pins because with some vendors
> they never worked correctly anyway. I don't know who still carries
> these.
>
> Are you absolutely certain the voltage is the problem? If you hook your
> Stamp to the PC does it seem to do what you expect? Something else to
> think about: if you are able to talk from the PC to the device through a
> straight cable, and you can talk from the Stamp to the PC with a
> straight cable, then you need a cross cable to talk between the Stamp
> and the device (how's that for a syllogism?).
>
> What is it that makes you certain it is a voltage-related issue?
>
> Al Williams
> AWC
> * Floating point A/D
> http://www.al-williams.com/awce/pak9.htm
>
>
>
> >
Original Message
> > From: tony.wells@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=UxKDjy5XEYxAUrhSzDpjRNi4-ZFWysOe-J17QQaEySSCzBwrKuSQ8OlUzF6VB7wgo_4CKF91R6aXdClhkXB2ZQ]tony.wells@a...[/url
> > Sent: Monday, January 21, 2002 4:13 PM
> > To: basicstamps@yahoogroups.com
> > Subject: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
> >
> >
> > Hi Folks,
> >
> > I'm trying to interface a Stamp to a serial device on TX and
> > RX which is
> > *very* fussy about the rs232 voltages. I've tried Max232 to
> > interface, but the device remains silent. This seems to be
> > becauseMax232 outputs a max of
> > +/- 8.5v unloaded and the device is loading it down to +/-8v which
> > +just
> > does not seem to be enough to wake up the device.
> >
> > It works fine however on my PC, which works at +12 and - 12v.
> > I know it is not my code because I've done lots of
> > subsitution testing to prove the assertion on the 8v issue.
> >
> > Does anyone know of a Max 232 type device which works to true
> > 12v or higher? I'm so desperate I'm willing to work with a
> > +/- 12v PSU to get this working.
> >
> > Any help would be appreciated.
> >
> > Thanks
> >
> > Tony Wells
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > 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/
> >
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> 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/
>
>
>
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
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Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
The MAX232A uses .1uF caps. The MAX232 uses 1uF caps.
Al Williams
AWC
* Easy RS-232 Prototyping
http://www.al-williams.com/awce/rs1.htm
>
Original Message
> From: peter verkaik [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=AnLOdpzBFgqrJc-QiImOmyygKojPPnq6gq3Z0pXgD-ifeTUGp4VTSsmjnAWMota_w2dXhDLHvtPjdGjAdxKgsQ]peterverkaik@b...[/url
> Sent: Monday, January 21, 2002 11:48 PM
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
>
>
> Hi,
>
> The max232 generates normally +/- 10V from a single 5V and
> requires four 0.1uF caps to do so. It may be your device
> draws a little bit more current than usual hence the -8V. I
> regarly use 10uF caps without problems and these keep the
> voltages to +/- 10V. With the increased caps you can draw
> more current without decreasing the voltages too much.
>
> Regards peter
>
>
>
Oorspronkelijk bericht
> Van: tony.wells@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=drJGvids_7xRfqk4RwVrW1_BB_JSSCoZ_sfKYtO0mjNeLoee7RRFuZ6W4GRzzgFMohfjfJzqEZKDVKG9d0mP]tony.wells@a...[/url
> Verzonden: maandag 21 januari 2002 20:25
> Aan: basicstamps@yahoogroups.com
> Onderwerp: Re: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
>
> AW wrote:
> > Are you absolutely certain the voltage is the problem? If you hook
> > your Stamp to the PC does it seem to do what you expect? Something
> > else to think about: if you are able to talk from the PC to
> the device
> > through a straight cable, and you can talk from the Stamp to the PC
> > with a straight cable, then you need a cross cable to talk
> between the
> > Stamp and the device (how's that for a syllogism?).
> >
> > What is it that makes you certain it is a voltage-related issue?
> >
>
> I'm aware of the 1488 thanks, but was hoping there was a 5v
> powered chip which outputs +/- 12v.
>
> I'm absolutely sure it is voltage related because::
>
> a. The external device (a Rugby MSF receiver) is normally
> powered from the rs232 line and when I connected the device
> to the PC I identified the pin supplying -12v from the PC
> which causes the device to wake up. When I simply move the
> same wire from the PC end and move it across to the Stamp
> Max232 equivalent which supples -8v the device goes back to
> sleep and remains as sleepy as Mr Sleepy in Sleepyville. When
> I move the wire back to the PC the device wakes up and is as
> alert as Mr Rabbit in a field of angry farmers!
>
> > Sorry to hear the MAX232 isn't working. +/- 5V is supposed
> to do the
> > trick.
> *Your* max232 is working fine - its was for another project
> which is done and dusted....
>
>
>
Original Message
> From: "Al Williams" <alw@a...>
> To: <basicstamps@yahoogroups.com>
> Sent: Monday, January 21, 2002 10:35 PM
> Subject: RE: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
>
>
> > Hi Tony,
> >
> > Sorry to hear the MAX232 isn't working. +/- 5V is supposed
> to do the
> > trick.
> >
> > The "traditional" way to go is a 1488 and 1489. One is the
> line driver
> > and the other is the line receiver. You provide +/- 12V and
> you are in
> > business. Don't mess with the ajustment pins because with
> some vendors
> > they never worked correctly anyway. I don't know who still carries
> > these.
> >
> > Are you absolutely certain the voltage is the problem? If you hook
> > your Stamp to the PC does it seem to do what you expect? Something
> > else to think about: if you are able to talk from the PC to
> the device
> > through a straight cable, and you can talk from the Stamp to the PC
> > with a straight cable, then you need a cross cable to talk
> between the
> > Stamp and the device (how's that for a syllogism?).
> >
> > What is it that makes you certain it is a voltage-related issue?
> >
> > Al Williams
> > AWC
> > * Floating point A/D http://www.al-williams.com/awce/pak9.htm
> >
> >
> >
> > >
Original Message
> > > From: tony.wells@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=drJGvids_7xRfqk4RwVrW1_BB_JSSCoZ_sfKYtO0mjNeLoee7RRFuZ6W4GRzzgFMohfjfJzqEZKDVKG9d0mP]tony.wells@a...[/url
> > > Sent: Monday, January 21, 2002 4:13 PM
> > > To: basicstamps@yahoogroups.com
> > > Subject: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
> > >
> > >
> > > Hi Folks,
> > >
> > > I'm trying to interface a Stamp to a serial device on TX and RX
> > > which is
> > > *very* fussy about the rs232 voltages. I've tried Max232 to
> > > interface, but the device remains silent. This seems to be
> > > becauseMax232 outputs a max of
> > > +/- 8.5v unloaded and the device is loading it down to
> +/-8v which
> > > +just
> > > does not seem to be enough to wake up the device.
> > >
> > > It works fine however on my PC, which works at +12 and -
> 12v. I know
> > > it is not my code because I've done lots of subsitution
> testing to
> > > prove the assertion on the 8v issue.
> > >
> > > Does anyone know of a Max 232 type device which works to
> true 12v or
> > > higher? I'm so desperate I'm willing to work with a
> > > +/- 12v PSU to get this working.
> > >
> > > Any help would be appreciated.
> > >
> > > Thanks
> > >
> > > Tony Wells
> > >
> > >
> > > To UNSUBSCRIBE, just send mail to:
> > > basicstamps-unsubscribe@yahoogroups.com
> > > 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/
> > >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > 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/
> >
> >
> >
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> 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/
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject
and Body of the message will be ignored.
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I use 10uF caps on the max232N. No sweat.
Regards peter
Oorspronkelijk bericht
Van: Al Williams [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=b31psb3ci4a5aQGNhTn87JHgGKYHxULwo5GaouaOLfR7Csym3MVAONYPok1AaZTAJBsTS4aGeCm7tHzJ]alw@a...[/url
Verzonden: dinsdag 22 januari 2002 05:29
Aan: basicstamps@yahoogroups.com
Onderwerp: RE: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
Hi Peter,
The MAX232A uses .1uF caps. The MAX232 uses 1uF caps.
Al Williams
AWC
* Easy RS-232 Prototyping
http://www.al-williams.com/awce/rs1.htm
>
Original Message
> From: peter verkaik [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=YReSCJpGeyo_FUKjMqVlD3vcsO_huCd892-7SQ2l3EvzeWxTiaTJEoEfsd4s75A_dZzQ3ZHHVxu1QRfDh8A8rAqzsMs]peterverkaik@b...[/url
> Sent: Monday, January 21, 2002 11:48 PM
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
>
>
> Hi,
>
> The max232 generates normally +/- 10V from a single 5V and
> requires four 0.1uF caps to do so. It may be your device
> draws a little bit more current than usual hence the -8V. I
> regarly use 10uF caps without problems and these keep the
> voltages to +/- 10V. With the increased caps you can draw
> more current without decreasing the voltages too much.
>
> Regards peter
>
>
>
Oorspronkelijk bericht
> Van: tony.wells@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=tcyo_lMF7MtaVCytHV0Ihx5-ss4sUGis0NX84_gulL9MZY8eHSsBTVeftoxHDeYwP7mFBu7pRocdIyC_kl5onw]tony.wells@a...[/url
> Verzonden: maandag 21 januari 2002 20:25
> Aan: basicstamps@yahoogroups.com
> Onderwerp: Re: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
>
> AW wrote:
> > Are you absolutely certain the voltage is the problem? If you hook
> > your Stamp to the PC does it seem to do what you expect? Something
> > else to think about: if you are able to talk from the PC to
> the device
> > through a straight cable, and you can talk from the Stamp to the PC
> > with a straight cable, then you need a cross cable to talk
> between the
> > Stamp and the device (how's that for a syllogism?).
> >
> > What is it that makes you certain it is a voltage-related issue?
> >
>
> I'm aware of the 1488 thanks, but was hoping there was a 5v
> powered chip which outputs +/- 12v.
>
> I'm absolutely sure it is voltage related because::
>
> a. The external device (a Rugby MSF receiver) is normally
> powered from the rs232 line and when I connected the device
> to the PC I identified the pin supplying -12v from the PC
> which causes the device to wake up. When I simply move the
> same wire from the PC end and move it across to the Stamp
> Max232 equivalent which supples -8v the device goes back to
> sleep and remains as sleepy as Mr Sleepy in Sleepyville. When
> I move the wire back to the PC the device wakes up and is as
> alert as Mr Rabbit in a field of angry farmers!
>
> > Sorry to hear the MAX232 isn't working. +/- 5V is supposed
> to do the
> > trick.
> *Your* max232 is working fine - its was for another project
> which is done and dusted....
>
>
>
Original Message
> From: "Al Williams" <alw@a...>
> To: <basicstamps@yahoogroups.com>
> Sent: Monday, January 21, 2002 10:35 PM
> Subject: RE: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
>
>
> > Hi Tony,
> >
> > Sorry to hear the MAX232 isn't working. +/- 5V is supposed
> to do the
> > trick.
> >
> > The "traditional" way to go is a 1488 and 1489. One is the
> line driver
> > and the other is the line receiver. You provide +/- 12V and
> you are in
> > business. Don't mess with the ajustment pins because with
> some vendors
> > they never worked correctly anyway. I don't know who still carries
> > these.
> >
> > Are you absolutely certain the voltage is the problem? If you hook
> > your Stamp to the PC does it seem to do what you expect? Something
> > else to think about: if you are able to talk from the PC to
> the device
> > through a straight cable, and you can talk from the Stamp to the PC
> > with a straight cable, then you need a cross cable to talk
> between the
> > Stamp and the device (how's that for a syllogism?).
> >
> > What is it that makes you certain it is a voltage-related issue?
> >
> > Al Williams
> > AWC
> > * Floating point A/D http://www.al-williams.com/awce/pak9.htm
> >
> >
> >
> > >
Original Message
> > > From: tony.wells@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=tcyo_lMF7MtaVCytHV0Ihx5-ss4sUGis0NX84_gulL9MZY8eHSsBTVeftoxHDeYwP7mFBu7pRocdIyC_kl5onw]tony.wells@a...[/url
> > > Sent: Monday, January 21, 2002 4:13 PM
> > > To: basicstamps@yahoogroups.com
> > > Subject: [noparse][[/noparse]basicstamps] 5V TTL to true rs232
> > >
> > >
> > > Hi Folks,
> > >
> > > I'm trying to interface a Stamp to a serial device on TX and RX
> > > which is
> > > *very* fussy about the rs232 voltages. I've tried Max232 to
> > > interface, but the device remains silent. This seems to be
> > > becauseMax232 outputs a max of
> > > +/- 8.5v unloaded and the device is loading it down to
> +/-8v which
> > > +just
> > > does not seem to be enough to wake up the device.
> > >
> > > It works fine however on my PC, which works at +12 and -
> 12v. I know
> > > it is not my code because I've done lots of subsitution
> testing to
> > > prove the assertion on the 8v issue.
> > >
> > > Does anyone know of a Max 232 type device which works to
> true 12v or
> > > higher? I'm so desperate I'm willing to work with a
> > > +/- 12v PSU to get this working.
> > >
> > > Any help would be appreciated.
> > >
> > > Thanks
> > >
> > > Tony Wells
> > >
> > >
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