1200 or 2400 Baud with an 8 or 16 bit microcontroller

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Hi,  Is there a way to do 1200 or 2400 baud with an 8 or 16 bit
microcontroller?

I have an application that requires modem communications.  In the past
I have done 110 - 300 baud half duplex with an 8 bit but now most
modems are not able to communicate below 1200 baud.  I would be
interested in finding 3rd party software routines that we can purchase
or get freeware.  I heard somewhere that some microcontroller vendors
offer this.

Any information would be appreciated.

Thank you

Bradley

Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
Most 8 and 16 bit microcontrollers are capable of doing well over
57.6kbaud, many can do several hundred kbaud. Units with built in UARTs
will be faster, but even simple micros without the UART hardware are
capable of impelmenting software UARTs that can operate at speeds of
38.4kbaud and higher. Equally, once you have picked your micro, assuming
it is one of the more commonly available types, it will usually have
application  notes available that show you how to implement a UART.

Cheers

Al

Bradley wrote:
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Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
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Correct me if I'm wrong, but my impression of the OP's posting is that
he wants to do the FSK/PSK/QAM/whatever in firmware, e.g. V.21, V.23,
V.22/bis, etc. I don't think you'll be doing V.34 etc etc in firmware
on a 16-bit micro unless it has an on-chip DSP :)

Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
snipped-for-privacy@larwe.com (Lewin A.R.W. Edwards) wrote in message
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You are correct, I want to do this in firmware and base speed
requirement needs to be 1200 or 2400 buad (v.22BIS).  PCB cost is
critical in the product.  We do not mind spending more time on
software getting the communications working. I do however "seem to"
remember that some microcontroller vendors actually offer this
software as a freebie or purchase.

Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
You've said this is a price critical product, yet are willing to spend $???
on software development !!
I can get real modems for less than $20C that are approved,replaceable and
very.very easy to program.
That $20 hardware is a LOT cheaper than HOURS and HOURS of trying to program
some other hardware solution.
Been there..done that..even the time spent 'on the net' should and must be
considered to the overall cost of the product

fwiw
jay



Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
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I've only seen high-speed softmodems available for ARM cores (you can
run K56flex on a 74MHz ARM7; probably slower, for that matter).

Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller

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Look at Scenix (Now Ubicom)

Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
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 Does this have to work on a fully open, any-dial-up, any host modem
basis (for 5+years), or do you have a more closed system.
Duplex, or simplex ?

 Challenge with uC solutions is the higher BAUD rates quickly
need Phase and Analog processing & line corrections.

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 They do, at lower end baud rates.

 Another 'cost optimise' approach, is to use two uC - rather than
one loaded up with everything, two smaller ones can work better.
 Look at TDK, they have a modem IC that is uC+Firmware, and use that
with your own now smaller/cheaper companion uC.
 IIRC Motorola have some SPI Modem Chips.
 
-jg

Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
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Lots of questions,  I would prefer that it work with any standard
modem or at least most standard modems for at least 5+ years.  This
application is industrial so if I understand the question a closed
system.

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I agree, a 2uC design might be the way to go.

Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
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 The TDK 73M2901CL sounds very close to what you need.
Means you can keep your present controller too :)

Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
Hi,

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No shortage of softmodems around. For a start:

<http://www.innovada.com/ ("embedded modem less than $3"), up to
V.32bis

<http://www.elektroniknet.de/d&e/softmodem/ (MSP430, auf Deutsch)

<http://www.motorola.com/mediacenter/news/detail/0,,2305_1886_23,00.html>
(press release, Motorola free reference design softmodem for ColdFire
MCF5407, auf Deutsch), the English product page is at
<http://e-www.motorola.com/webapp/sps/site/prod_summary.jsp?code=RDCFSM&parentCode=MCF5407&nodeId02%VS0lT2RSknbsK7cj>

Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller

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Also be careful with 1200 and 2400 baud speeds with current modems.  Some
very popular ones don't really support these rates, even though they say
they do.  This rate is below what typical modem makers find useful.
Everyone wants to go faster, so the low end has reallly suffered.

I found tech support from the major modem makers absolutely horrible 2-3
years ago.  If you're not putting it on a PC and using standard windows
drivers the tech support is useless.

If you're looking to embed a modem in a project, I had very good results
with the Multi-tech embeddable modem modules.

Scott



Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
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Be especially leery of 1200 baud modems.  During their heyday
there were various incompatible standards.  By the time 2400 came
along standards kept them compatible.

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   Available for consulting/temporary embedded and systems.
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Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
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Man, my memory may be going but...

Didn't pretty much everyone settle on v.22 for Async 1200bps?  I know
for Sync 1200bps there were at least three different standards (Bell,
Europe and Racal-Vadic), and European and U.S. 300bps standards were
different.  Or was it that the U.S. was using 212A at 1200 and then
everyone merged together at 2400bps with v.22bis?

Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
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The last.

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Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller

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Absolutely

Check out Microchip's (PIC) website www.microchip.com. Under the "Engineer's
toolbox" you will find a wealth of information, application notes, and
sample code for all
sorts of asynchronous communications.

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Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
been there..done that

The most reliable way is to take an off the shelf modem and wire it up to
the microcontroller.
I did this with 8052 and 2400Baud modems several years ago for remote energy
control systems. It got around all the hassles of DOC( FCC in USA)
requirements and made it simple to replace the modem card in case it got
fried. I used a desktop 'motherboard-daughterboard' expander to join the two
together.
Programming was a snap, took, oh a couple of hours more or less.

Hmm...12 years and still working.....
Now if what you want to do is doit all in software,well, that's another
story. Sorry, I went for the easy and reliable way..

hth
jay



Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
You suggestion bears merit. I have come from an environment where PCB
cost has been critical.  That is why we used 110 and 300 baud half
duplex which only worked with a small number of modems.  Now I am in
an environment where it is a bit different.  For one of my
applications I can afford to use a real modem.  The other application
is still very PCB cost sensitive and I would like to recieve or
purchase tested bit banging software for use on an 8 or 16 bit micro.

Bradley



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Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
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<Technical nitpick>  With modems 1200 bps and up, baud != bps.  Baud is
the rate of carrier shift, and at modem speeds above 300 bps, they use
more than two states to transfer more than one bit per shift.  For
example, if a modem is 400 baud with 8 states, each shift transfering 3
bits, that gives 1200 bps.

I lost interest in how modems work after 9600 bps and the Telebit/HST
flamewars.  Now they approach 56kbps by use of black magic voodoo.  :^)
</Technical nitpick>

--
Ron Sharp.



Re: 1200 or 2400 Baud with an 8 or 16 bit microcontroller
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Another technical nitpick: Bell 202 was 1200 baud FSK (baud == bps) half
duplex. Well, technically there was a low-speed reverse-channel (5 buad),
but I don't know of of the back-channel ever being in the real world, and
most of the Bell-202 modem chips on the market don't even support th
ereverse-channel. Bell 202 is still in use in millions of telemtry and
industrial control applications (esp. ones that use the HART protocol).

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