Help need : I need more than 2 UARTs

Started by Christophe September 30, 2006
Hello,

I'am trying to set up an application with an Xbee module and an
graphical display, both with an serial interface. As far as I
understand, there are only 2 uarts on my LPC2138 board. I would like
to keep UART 0 for programing and communication with the module, so I
need one more uart. What is the best way to achieve that ? SPI to UART
converter like the MAX3100, or perhaps a I2C to UART circuit, or
perhaps is it possible to emulate an uart with GPIO... Any advices
will be appreciate.

Thanks for your help,
Best regards,
Christophe.

An Engineer's Guide to the LPC2100 Series

Christophe wrote:
>
> Hello,
>
> I'am trying to set up an application with an Xbee module and an
> graphical display, both with an serial interface. As far as I
> understand, there are only 2 uarts on my LPC2138 board. I would like
> to keep UART 0 for programing and communication with the module, so I
> need one more uart. What is the best way to achieve that ? SPI to UART
> converter like the MAX3100, or perhaps a I2C to UART circuit, or
> perhaps is it possible to emulate an uart with GPIO... Any advices
> will be appreciate.
>
Well, you've named all the possible solutions. So start looking at the
tradeoffs and pick one.

TomW

--
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net http://cyberiansoftware.com http://openzipit.org
"Windows? No thanks, I have work to do..."
----------------
In my current project, I'm using a LPC915 device connected to the
I2C bus of a LPC2148. It acts as a I2C slave implementing a circular
buffer on the UART side. Using an "intelligent" device like that,
enables one to add some "pre-processing" to the uart data....
The LPC915 ius cheap too, has internal osc, much cheaper than the
MAX3100 solution...It would be very easy to scale this solution,
just add more LPC915 on the I2C bus...(depends ofcourse on the
amount of data that needs to be sent/received over the uart !)

Regards,
Carsten Groen

--- In l..., Tom Walsh wrote:
>
> Christophe wrote:
> >
> > Hello,
> >
> > I'am trying to set up an application with an Xbee module and an
> > graphical display, both with an serial interface. As far as I
> > understand, there are only 2 uarts on my LPC2138 board. I would
like
> > to keep UART 0 for programing and communication with the module,
so I
> > need one more uart. What is the best way to achieve that ? SPI
to UART
> > converter like the MAX3100, or perhaps a I2C to UART circuit, or
> > perhaps is it possible to emulate an uart with GPIO... Any
advices
> > will be appreciate.
>
--- In l..., Tom Walsh wrote:
>
> Christophe wrote:
> >
> > Hello,
> >
> > I'am trying to set up an application with an Xbee module and an
> > graphical display, both with an serial interface. As far as I
> > understand, there are only 2 uarts on my LPC2138 board. I would
like
> > to keep UART 0 for programing and communication with the module,
so I
> > need one more uart. What is the best way to achieve that ? SPI
to UART
> > converter like the MAX3100, or perhaps a I2C to UART circuit, or
> > perhaps is it possible to emulate an uart with GPIO... Any
advices
> > will be appreciate.
> >
> Well, you've named all the possible solutions. So start looking
at the
> tradeoffs and pick one.
>
> TomW

Tom: all solutions? some of the responses to this post have flushed
out a couple not on the original list, notably adding a cheap micro.

I guess that was the intent of the original post. Hardly deserving
the abrupt response above.

Brendan.
--- In l..., Carsten Gr wrote:
>
> In my current project, I'm using a LPC915 device connected to the
> I2C bus of a LPC2148. It acts as a I2C slave implementing a circular
> buffer on the UART side. Using an "intelligent" device like that,
> enables one to add some "pre-processing" to the uart data....
> The LPC915 ius cheap too, has internal osc, much cheaper than the
> MAX3100 solution...It would be very easy to scale this solution,
> just add more LPC915 on the I2C bus...(depends ofcourse on the
> amount of data that needs to be sent/received over the uart !)
>
> Regards,
> Carsten Groen

We do something similar with a LPC2134 - the same micro as the main
system's one. The main system uses both UARTs: we implemented an I2C
to UART on the 2nd LPC2134 for a (plug-in) debug port (i.e. it's only
used for development, not for the main product). I'm not suggesting
you use anything as powerful if it's to be included in the main
system, but the setup works well: there are plenty of cheap 8-bit
micros, that work out quite cost effective. The can also be used as
a "port expander" for other IO as well.

Brendan