What is the baud rate?
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Posts: 46,084
I've heard about the baud rate, I know you need it in commands such
as serin and serout, but I want to understand what it actually is.
Please can someone explain this to me. Is it the frequency? Thanks.
as serin and serout, but I want to understand what it actually is.
Please can someone explain this to me. Is it the frequency? Thanks.
Comments
byte actually requires 10 bits to send because there is a start bit and (at
N-8-1) as stop bit. So, at 9600 baud, you can send about 960 bytes per
second.
Jan Axelson's "Serial Port Complete" is a good reference book for serial
communications.
-- Jon Williams
-- Parallax
In a message dated 3/10/2003 11:28:02 AM Central Standard Time,
e99bf0e8@s... writes:
> I've heard about the baud rate, I know you need it in commands such
> as serin and serout, but I want to understand what it actually is.
> Please can someone explain this to me. Is it the frequency? Thanks.
>
[noparse][[/noparse]Non-text portions of this message have been removed]
clearly.....but now can I just ask you to clarify the difference
between baud rate and baud mode? Are they the same? Thanks again.
--- In basicstamps@yahoogroups.com, jonwms@a... wrote:
> The baud rate is the transmission rate in bits per second.
Technically, an
> byte actually requires 10 bits to send because there is a start bit
and (at
> N-8-1) as stop bit. So, at 9600 baud, you can send about 960 bytes
per
> second.
>
> Jan Axelson's "Serial Port Complete" is a good reference book for
serial
> communications.
>
> -- Jon Williams
> -- Parallax
>
>
> In a message dated 3/10/2003 11:28:02 AM Central Standard Time,
> e99bf0e8@s... writes:
>
> > I've heard about the baud rate, I know you need it in commands
such
> > as serin and serout, but I want to understand what it actually
is.
> > Please can someone explain this to me. Is it the frequency?
Thanks.
> >
>
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
rate of communications, but the level of 1 and 0 bits, and how [noparse][[/noparse]for SEROUT]
the serial line is driven.
See the manual for details.
-- Jon Williams
-- Parallax
In a message dated 3/10/2003 11:43:23 AM Central Standard Time,
e99bf0e8@s... writes:
> Thanks for answering my question, that explained it very
> clearly.....but now can I just ask you to clarify the difference
> between baud rate and baud mode? Are they the same? Thanks again.
[noparse][[/noparse]Non-text portions of this message have been removed]
Here is one definition on the web:
http://www.its.bldrdoc.gov/fs-1037/dir-004/_0559.htm
If you need a rough rule-of-thumb, divide the stated baud rate by 10 to get
an approximate character transmission rate; e.g., 9600 baud is approximately
960 characters per second. This guideline comes from the following
assumptions: short messages, a standard 8-bit character, required start and
stop bits, and usual inter-character delays.
HTH,
Daniel
Original Message
From: Caryatnid [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=UkSGQwCITQmGuPRvrmg6HrJhqUk6dqkWsCtHkCAjvCLq0_ngsva3FLHjD3KVOgm1y3jVuF-Lm2aKJlG77xqYJQ]e99bf0e8@s...[/url
Sent: Monday, March 10, 2003 12:27 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] What is the baud rate?
I've heard about the baud rate, I know you need it in commands such
as serin and serout, but I want to understand what it actually is.
Please can someone explain this to me. Is it the frequency? Thanks.
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For example, 1200 baud means the signal can change its value 1200
times in a second.
Bit per second, or bps is not necessarily the same as baud rate. If
the voltage used to represent signal has only two states (ie - +5v,
0v, like on a BASIC STAMP) then baud is the same as bps. If the
voltages used to represent a signal that has multiple states then the
bits per second will be higher than the actual baud rate.
MODEMS, for example, trasmit at 2400 baud. It is a physical
limitation on the phone line. However, due to sophisticated data
transmission technics and data compression MODEMS are able to
transmit signals up to about 56kbps (although the federal government
places limitations on this speed), even though the actual baud rate
is 2400.
However, to reiterate, when you are talking about data transmission
with wire-to-wire digital comunications (like with a STAMP), baud
rate is the same as bps.
-Dustin
--- In basicstamps@yahoogroups.com, "Caryatnid" <e99bf0e8@s...> wrote:
> I've heard about the baud rate, I know you need it in commands such
> as serin and serout, but I want to understand what it actually is.
> Please can someone explain this to me. Is it the frequency? Thanks.
the number of data bits to be sent (7 or 8) and the
'parity' bit (None, or Even). In the Stamp, there
is the added feature of an Open Collector mode
(which allows multiple output pins to be connected
in a 'party line' without damage).
Also 'normal' 232 drivers invert their data, so the
Stamp has an option for driving with (no driver)
or without (has driver, Invert) an external 232 driver.
The SEROUT command allows you (the programmer) to
add in these parameters with the baud rate selector,
to produce a 'Baud Mode'.
SerOpenCol CON $8000 ' If Set, use OpenCollector
(Drive to 0, float to +5 if 'Normal' inversion)
SerInvert CON $4000 ' If Set, use 'Invert' mode (with 232 driver)
' If clear, use 'Normal' (no external drivers)
SerParity CON $2000 ' If Set, use 7 Data, Even Parity.
' If clear, 8 data, No parity (default)
Usual use of the BS2 Programming Port is:
SEROUT, 16, 84 + SerInvert, [noparse][[/noparse]"Hi"]
' ie Pin 16, 9600 baud, Inverted -- because the BS2 has an
' on module 232 driver on the programming port
Now, for how to find that '84', you really DO need the manual.
--- In basicstamps@yahoogroups.com, jonwms@a... wrote:
> The baudmode parameter for SERIN and [noparse][[/noparse]particularly] SEROUT not only
set the
> rate of communications, but the level of 1 and 0 bits, and how [noparse][[/noparse]for
SEROUT]
> the serial line is driven.
>
> See the manual for details.
>
> -- Jon Williams
> -- Parallax
>
>
> In a message dated 3/10/2003 11:43:23 AM Central Standard Time,
> e99bf0e8@s... writes:
>
> > Thanks for answering my question, that explained it very
> > clearly.....but now can I just ask you to clarify the difference
> > between baud rate and baud mode? Are they the same? Thanks again.
>
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]