serial to ttl
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Posts: 46,084
I am trying to interface a Stamp's SEROUT to an OOPIC. Is there a
simple solution to invert the signal and to ttl voltage levels.
simple solution to invert the signal and to ttl voltage levels.
Comments
(usually) get away with driving the RS232 port's receive pin directly
from a Stamp. This is out of the RS232 spec but it usually works. If it
doesn't work, you can't blame anyone because it isn't supposed to work,
but it usually works.
The trick is connecting the RS232 transmitter to the Stamp. Put a 22K
resistor in series between the RS232 transmitter and the Stamp's receive
pin. When the Stamp "sees" a voltage over 5V, the internal protection
diodes will turn on clamping the input pin to about 5.7V. The So a 12V
input through the 22K resistor will result in (12-5.7)/22000 which is
not enough current to blow the protection diodes.
Then you have to set the Stamp to use a non-inverted baud mode. This is
kind of a hack. It is not as noise immune nor can you get away with it
over long cables.
If you want real RS232 have a look at http://www.al-williams.com/rs1.htm
-- these boards use a MAX232 to get real RS232 in and out. It is a kit,
so you can usually work it into whatever you are building (or put the
pins we supply in and it fits nicely in a solderless breadboard).
If you read the SERIN/SEROUT manual pages, you'll find all of this is
explained. Also have a look at http://www.wd5gnr.com/stampfaq.htm -- a
lot of related info there too.
Al Williams
AWC
* 8 channels of PWM
http://www.al-williams.com/awce/pak5.htm
>
Original Message
> From: elscottyrmt [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=K3bpAvSOGN4KdvAd8opd2AJg8ad7eYEnuUBwTtqyI5yn84dKyEQAKEN3JL25dmgqhKHJQsAi9l-Hxm4nqlI5lA5D]scottlosoya@c...[/url
> Sent: Saturday, May 31, 2003 1:00 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] serial to ttl
>
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> I am trying to interface a Stamp's SEROUT to an OOPIC. Is there a
> simple solution to invert the signal and to ttl voltage levels.
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pins and specify a "true" baudmode value. This will generate
TTL-level, non-inverted serial data as expected by your OOPIC. A
wire would be the only further interface needed.
Regards,
Steve
On 31 May 03 at 6:00, elscottyrmt wrote:
> I am trying to interface a Stamp's SEROUT to an OOPIC. Is there a
> simple solution to invert the signal and to ttl voltage levels.